Method and device for determining digital value indicative of physical quantity to be measured

Abstract

The invention relates to a method and a device for determining a digital value indicative of a physical quantity to be measured. A method (1000) of providing a digital value (Dout) indicative of a physical quantity to be measured by a sensor circuit or bridge circuit having two excitation nodes (E1, E2) and at least one output node (RO1, RO2), the method comprising the steps of: a) applying (1002) a time-varying bias signal to the excitation nodes, such that at least one output node provides a time-varying output signal (Vp, Vn); b) determining (1003) a first time value (T1) or a first count value (N1) or a first index (Index1) associated with a first event (event1) at which the first output signal (Vp) exceeds the first threshold signal (Vt1); c) providing (1004) a digital value (Dout) indicative of the physical quantity to be measured based on the at least one time value (T1) or count value (N1) or index value (Index1).

Description

Technical Field

[0001] The present invention relates generally to the field of digitization methods and circuits, and more particularly to methods and circuits for digitizing the differential output of a sensor circuit or bridge circuit having two excitation nodes (also referred to as "input nodes") and two readout nodes (also referred to as "output nodes"). The present invention also relates to an integrated circuit comprising such a sensor or bridge and a digitization circuit. Background Art

[0002] Figure 1 is a schematic representation of a horizontal Hall element with two excitation nodes E1, E2 (or "input nodes") and two readout nodes RO1, RO2 (or "output nodes"). When a constant voltage (commonly referred to as a "bias voltage") is applied to the input nodes, a current will flow through the Hall element. In the absence of a magnetic field, the voltages v1, v2 at the output nodes are equal, and thus the differential voltage Vdiff (Vdiff) across these nodes will be equal to zero. In the presence of a magnetic field oriented perpendicular to the Hall element, the voltage levels at the output nodes will be different, and a differential voltage Vdiff will appear across the output nodes RO1, RO2.

[0003] Figure 2A is a schematic representation of a Wheatstone bridge comprising four resistors R1, R2, R3, R4 (e.g., magnetoresistive elements or piezoresistive elements). The bridge has two parallel branches, each branch comprising two resistors connected in series. The bridge has two excitation nodes (or "input nodes") E1, E2 and two readout nodes (or "output nodes") RO1, RO2. When the four resistance values ​​R1 to R4 are equal, the bridge is in balance and the output voltages v1, v2 are equal, so the differential voltage Vdiff at the output nodes is zero. When one of the resistance values ​​changes, the bridge is no longer balanced and a voltage difference Vdiff will appear at the output node.

[0004] Figure 3 A method for performing a differential voltage signal Vdiff (such as, for example, Figure 1 The differential output voltage of the Hall element or Figure 2A The sensing and digitization circuit includes a differential amplifier followed by a classical analog-to-digital converter (ADC). The ADC provides a digital value Dig_value corresponding to the differential voltage Vdiff, which indicates the physical value to be measured (for example, in the case where Vdiff comes from a horizontal Hall element, the physical value is a magnetic field component; or, for example, in the case where Vdiffs comes from a Wheatstone bridge with a piezoresistive element, the physical value is a pressure value; etc.).

[0005] Many different types of ADCs are available, having different characteristics in terms of conversion speed, power consumption, accuracy, space occupied (eg, silicon area), etc.

[0006] There is always room for improvement or substitution. Summary of the invention

[0007] An object of embodiments of the present invention is to provide a method and circuit for providing a digital value indicative of a physical quantity to be measured by a sensor circuit or a bridge circuit having two excitation nodes (or "input nodes") and at least one readout node (or "output node") (e.g., two output nodes, or three output nodes).

[0008] Another object of embodiments of the present invention is to provide an integrated circuit comprising such a sensor circuit or a bridge circuit and such an evaluation or processing circuit.

[0009] It is an object of certain embodiments of the invention to provide such an integrated sensor device with error detection capabilities.

[0010] These and other objects are achieved by embodiments of the present invention.

[0011] According to a first aspect, the present invention provides a method of providing a digital value (e.g., Dout) indicative of a physical quantity to be measured by a sensor circuit or a bridge circuit, the sensor circuit or the bridge circuit having two excitation nodes (e.g., E1, E2) and at least one output node (e.g., RO1, RO2) (e.g., two readout nodes), the method comprising the following steps: a) applying a time-varying bias signal (e.g., Vbias) (e.g., a bias voltage or a bias current) to the excitation nodes (e.g., E1, E2) so that at least one output node (e.g., RO1, RO2) provides at least one time-varying output signal (e.g., Vp, Vn) (e.g., Vp, Vn) For example, output voltage or output current); c) determining at least one time value (for example, T1) or at least one count value (for example, N1) or at least one index value (for example, index1) associated with a first event (for example, event1), at which first event (for example, event1) at which at least one read signal (for example, Vp) exceeds at least one threshold signal (for example, Vt); d) determining a digital value (for example, Dout) indicating the physical quantity to be measured based on the at least one time value (for example, T1) or the at least one count value (for example, N1) or the at least one index value (for example, index1).

[0012] The method according to the first aspect can also be expressed as follows: A method for providing a digital value (e.g., Dout) indicating a physical quantity to be measured by a sensor circuit or a bridge circuit, the sensor circuit or the bridge circuit having two excitation nodes (e.g., E1, E2) and at least one output node (e.g., RO1, RO2) (e.g., two readout nodes), the method comprising the following steps: a) applying a time-varying bias signal (e.g., Vbias) (e.g., a bias voltage or a bias current) having, for example, a predefined waveform or a configurable waveform to the excitation nodes (e.g., E1, E2) so that at least one output node (e.g., RO1, RO2) provides at least one time-varying output signal (e.g., Vp, Vn) (e.g., an output voltage or an output current); b) using (e.g., considering and and / or generate) at least one threshold signal (Vt), which has a predefined value or a configurable value or a predefined waveform or a configurable waveform; c) determine at least one time value (e.g., T1) or at least one count value (e.g., N1) or at least one index value (e.g., index1) related to a first event (e.g., event1), at which time at least one readout signal (e.g., Vp) exceeds at least one threshold signal (e.g., Vt); d) determine a digital value (e.g., Dout) indicating a physical quantity to be measured based on the at least one time value (e.g., T1) or the at least one count value (e.g., N1) or the at least one index value (e.g., index1).

[0013] Step d) may take into account the waveform of the bias signal, and / or the value or waveform of the threshold signal, explicitly or implicitly, for example by means of the first and / or second reference numbers and / or by means of one or more parameters.

[0014] Step d) may include using a predefined lookup table, or using one or more predefined mathematical formulas. For example, if only one predefined (i.e., known) bias waveform can be applied in step a), and if only one threshold or threshold signal (e.g., repeating the same threshold) can be applied in step b), there is a 1-to-1 relationship between the digital value and T1, or between the digital value and N1, or between the digital value and Index1, and the details of the waveform of the bias signal and / or threshold signal are not required in step d). In fact, they can be considered in the values ​​of the lookup table, or in the parameter values ​​or coefficients of (one or more) predefined mathematical functions.

[0015] However, if one from at least two different bias waveforms can be applied in step a), and / or if one from at least two thresholds or threshold signals can be applied in step b), then step d) may require knowing which of these bias waveforms and / or which of these thresholds or signals was actually used, but again, no characteristics of the waveforms themselves or of the thresholds themselves are required, and one or more references (e.g. one or more numbers) indicating which of the predefined bias waveforms and / or thresholds or threshold waveforms were used may be sufficient.

[0016] The predefined lookup table may be a predefined table determined during design or during simulation, or may be measured during calibration and stored in a non-volatile memory (e.g. a non-volatile memory of a sensor device comprising the sensor circuit and preferably also comprising a circuit for generating a bias waveform and a threshold signal), for example without any selection parameter (if only one specific bias waveform and only one specific threshold signal may be generated), or based on a selection parameter for the bias waveform (e.g. if the bias waveform may be selected from a plurality of predefined waveforms) and / or based on a selection parameter for the threshold signal (if the threshold waveform may be selected from a plurality of predefined waveforms) and / or based on one or more thresholds (e.g. a first value for Vt1 and a second value for Vt2).

[0017] The expression "using a predefined lookup table" may include performing linear interpolation.

[0018] The predefined mathematical formula can be a polynomial expression in one variable, for example, used to convert a single time value (T1) or a single count value (N1) or a single index value (index1) into the physical quantity, and the formula is applicable to a specific waveform of Vbias and a specific threshold or a specific threshold function.

[0019] In an embodiment, the bias signal is selected from a first group of a finite set of possible candidate bias signals and the threshold signal is selected from a second group of a finite set of possible values ​​or threshold signals, and step d) considers which candidate from the first group is used, and which candidate from the second group is used.

[0020] In an embodiment, the bias signal is a single predefined waveform and the threshold signal is a constant value within a given measurement cycle, but may change between different measurement cycles. In this case, a two-dimensional lookup table may be used in step d), or a mathematical formula of two variables (e.g., a first variable corresponding to the measured time or count or index, and a second variable or parameter corresponding to the applied threshold) may be used in step d).

[0021] In a preferred embodiment, steps a) to d) are performed (eg, repeatedly performed (eg, periodically performed)) at least twice.

[0022] In an embodiment, step b) comprises: using a single threshold signal (e.g., Vt) having a predefined or configurable value or a predefined or configurable waveform;

[0023] And step c) includes: determining a single time value (e.g., T1) or a single count value (e.g., N1) or a single index value (e.g., index1) associated with a single event (e.g., event1), at which the at least one output signal (e.g., Vp or Vn) exceeds the single threshold signal (e.g., Vt); and step d) includes: determining the digital value (e.g., Dout) based on the single time value (e.g., T1) or count value (e.g., N1) or index value (e.g., index1).

[0024] As mentioned above, step d) may take into account the waveform of the bias signal (Vbias) used in step a) (e.g., a reference to the waveform of the bias signal (Vbias) used in step a) or a parameter of the waveform of the bias signal (Vbias) used in step a)), and / or may take into account the value or waveform of the threshold signal used in step b) (e.g., a reference to the waveform of the threshold signal used in step b) or a parameter of the waveform of the threshold signal used in step b)).

[0025] In an embodiment, Dout is a function of T1 as well as a bias waveform and a threshold.

[0026] In an embodiment, Dout is a function of N1 as well as a bias waveform and a threshold.

[0027] In an embodiment, Dout is a function of index1 as well as a bias waveform and a threshold.

[0028] In an embodiment, only one predefined bias waveform is used in step a) and only one predefined threshold is used in step b) and Dout is determined in step d) as a function of T1 or N1 or index1.

[0029] In an embodiment, Dout is determined as the result of a lookup table using T1 or N1 as an index (optionally with interpolation).The lookup table may take into account the details of the bias waveform and the details of the threshold.

[0030] In an embodiment, Dout is determined as the result of a polynomial expression of a single variable T1 or N1 or index 1. The coefficients of the polynomial expression may take into account the details of the bias waveform and the details of the threshold.

[0031] In an embodiment, the sensor circuit or the bridge circuit has two output nodes (e.g., RO1, RO2); and step a) causes the two output nodes (e.g., RO1, RO2) to provide a first time-varying output signal (e.g., Vp) and a second time-varying output signal (e.g., Vn); and step b) includes: using (e.g., generating) a first threshold signal (e.g., Vt, Vt1), the first threshold signal (e.g., Vt, Vt1) having a first predefined value or a first configurable value or a first predefined waveform, and using (e.g., generating) a second threshold signal (e.g., Vt, Vt2), the second threshold signal (e.g., Vt, Vt2) is equal to or different from the first threshold signal, the second threshold signal has a second predefined value or a second configurable value, or a second predefined waveform; and the method further comprises step e): generating a time-varying common mode signal (e.g., Vcm (Vcommon mode)) as R*Vbias or as (Vp+Vn) / 2, where R is a predefined ratio and Vbias is a bias signal (e.g., a bias voltage); and wherein step c) comprises: determining a time-varying common mode signal (e.g., Vcm (Vcommon mode)) associated with a first event (e.g., event1) A first time value (e.g., T1) or a first count value (e.g., N1) or a first index value (e.g., index1) is determined, and at a first event, a first output signal (e.g., v1, Vp) exceeds a first threshold signal (e.g., Vt1); and a second time value (e.g., T2) or a second count value (e.g., N2) or a second index value (e.g., index2) associated with a second event (e.g., event2) is determined, and at the second event, a common mode signal (e.g., Vcm) exceeds a second threshold signal (e.g., Vt, Vt2); and wherein, step Step d) includes determining the digital value (e.g., Dout) based on the first time value and the second time value (e.g., T1, T2), or based on the first count value and the second count value (e.g., N1, N2), or based on the first index value and the second index value (e.g., index1, index2), or based on the difference between the first time value and the second time value (e.g., ΔT), or based on the difference between the first count value and the second count value (e.g., ΔN), or based on the difference between the first index value and the second index value (e.g., Δindex).

[0032] In an embodiment, a common mode signal (eg, a common mode voltage (eg, Vcm)) is generated as an average of two sense voltages (eg, Vp, Vn) or by adding the two sense voltages and dividing the sum by two.

[0033] In an embodiment, the common mode signal (eg, common mode voltage (eg, Vcm)) is generated as a predefined ratio of the bias voltage applied in step a) or as a predefined ratio of the supply signal (eg, supply voltage or supply current).

[0034] As mentioned above, step d) may take into account the waveform of the bias signal (Vbias) used in step a) and / or may take into account the value(s) or waveform(s) of the threshold signal(s) used in step b).

[0035] In an embodiment, step b) includes: using (e.g., generating) a first threshold signal (e.g., Vt, Vt1), the first threshold signal (e.g., Vt, Vt1) having a first predefined value or a first configurable value, or a first predefined waveform, and using (e.g., generating) a second threshold signal (e.g., Vt, Vt2), the second threshold signal (e.g., Vt, Vt2) being equal to or different from the first threshold signal, the second threshold signal having a second predefined value or a second configurable value, or a second predefined waveform; and step c) includes: determining a first time value (e.g., T1) or a first count value (e.g., N1) or a first index value (e.g., index1) associated with a first event (e.g., event1), at which the first output signal (e.g., v1, Vp) exceeds the first threshold signal (e.g., Vt, Vt1); and using a predefined second time value (e.g., T2ref (T2 reference)) or a predefined second count value associated with a second event (e.g., event2) (e.g., N2ref (N2 reference)) or a second index value (e.g., index2ref (index 2 reference)), at a second event, the common mode signal (e.g., Vcm) exceeds a second threshold signal (e.g., Vt, Vt2), the common mode signal is, for example, R*Vbias or as (Vp+Vn) / 2, where R is a predefined ratio and Vbias is a bias signal (e.g., bias voltage); and wherein step d) includes: determining the digital value (e.g., Dout) based on the first time value and the second time value (e.g., T1, T2ref), or based on the first count value and the second count value (e.g., N1, N2ref), or based on the first index value and the second index value (e.g., index1, index2ref), or based on the difference between the first time value and the second time value (e.g., ΔT), or based on the difference between the first count value and the second count value (e.g., ΔN), or based on the difference between the first index value and the second index value (e.g., Δindex).

[0036] As mentioned above, step d) may take into account the waveform of the bias signal (Vbias) used in step a) and / or may take into account the value(s) or waveform(s) of the threshold signal(s) used in step b).

[0037] In an embodiment, at least one threshold signal or threshold (eg, Vt; Vtp, Vtn) has a predefined voltage level or a predefined value.

[0038] In an embodiment, at least one threshold signal (eg, Vt; Vtp, Vtn) has a configurable voltage level or a configurable value.

[0039] In an embodiment, at least one threshold signal or value (e.g., Vt) is dynamically adjustable between two measurements, but is not dynamically adjustable during a single measurement (or digitization step) (i.e., within a Figure 5 During the time period T-ramp (T_ramp) it remains stable.

[0040] In an embodiment, the at least one threshold signal is generated by a digital-to-analog converter (DAC).

[0041] In an embodiment, at least one threshold signal is generated (eg, using a PWM module) as a PWM signal followed by a low pass filter (LPF).

[0042] In an embodiment, at least one threshold signal (e.g., Vt; Vtp, Vtn) is equal to a predefined ratio of the maximum bias signal, or a predefined ratio of the supply signal (e.g., supply voltage). The predefined ratio may be defined using a voltage divider comprising at least two resistors connected in series, or in any other suitable manner. In an embodiment, the value of the threshold signal is a predefined portion or fraction (e.g., 50%) of Vbias or a predefined portion or fraction (e.g., 50%) of the supply voltage VSS. The value of the portion may be defined by the resistance value of the at least two resistors connected in series.

[0043] In an embodiment, the sensor circuit or the bridge circuit has two output nodes (e.g., RO1, RO2); and step b) includes: using (e.g., generating) a first threshold signal (e.g., Vt, Vt1), the first threshold signal (e.g., Vt, Vt1) having a first predefined value or a first configurable value, or a first predefined waveform, and using (e.g., generating) a second threshold signal (e.g., Vt, Vt2), the second threshold signal (e.g., Vt, Vt2) being equal to or different from the first threshold signal, having a second predefined value or a second configurable value, or a second predefined waveform; and step a) enables the two output nodes (e.g., RO1, RO2) to provide a first time-varying output signal (e.g., Vp) and a second time-varying output signal (e.g., Vn); and step c) includes: determining a first time value (e.g., T1) or a first count value (e.g., N1) or a first index value (e.g., index1) associated with a first event (e.g., event1), in the first At an event, the first output signal (e.g., Vp) exceeds the first threshold signal (e.g., Vt, Vt1); and a second time value (e.g., T2) or a second count value (e.g., N2) or a second index value (e.g., index2) associated with a second event (e.g., event2) is determined, and at the second event, the second output signal (e.g., Vn) exceeds the second threshold signal (e.g., Vt, Vt2); and step d) includes: determining the digital value (e.g., Dout) based on the first time value and the second time value (e.g., T1, T2), or based on the first count value and the second count value (e.g., N1, N2), or based on the first index value and the second index value (e.g., index1, index2), or based on the difference between the first time value and the second time value (e.g., ΔT), or based on the difference between the first count value and the second count value (e.g., ΔN), or based on the difference between the first index value and the second index value (e.g., Δindex).

[0044] As mentioned above, step d) may take into account the waveform of the bias signal (Vbias) used in step a) and / or may take into account the value(s) or waveform(s) of the threshold signal(s) used in step b).

[0045] In an embodiment, the method further includes: determining a first threshold value (e.g., Val1) and a second threshold value (e.g., Val2), and applying these values ​​to at least one digital-to-analog converter to generate a first threshold signal and a second threshold signal (e.g., Vt1, Vt2), and dynamically adjusting these values ​​(e.g., Val1, Val2) in a control loop so that the first event is substantially consistent with the second event, or so that the difference between the first time value and the second time value (e.g., T1, T2), or the difference between the first count value and the second count value (e.g., N1, N2) is substantially equal to a predefined value; and step d) includes: treating the first threshold value and the second threshold value (e.g., Val1, Val2) as a first index value and a second index value, and determining the digital value (e.g., Dout) based on the first index and the second index (e.g., index1, index2), or based on the difference between the first index and the second index (e.g., Δindex).

[0046] In this embodiment, step d) may take into account the waveform of the bias signal (Vbias) used in step a), for example explicitly or implicitly in each period, if different bias waveforms are used, but this need not be done if only a single bias waveform is used.

[0047] Step d) may take into account a predefined difference (or offset) between T1 and T2 of the control loop, or a predefined difference between N1 and N2, if the difference is configurable, but in a preferred embodiment the difference (or offset) is not configurable.

[0048] In embodiments where the bias waveform is a single waveform and the predefined difference value of the control loop is fixed (e.g., hard-coded), the digital value "Dout" can be uniquely determined based on the value Δindex, for example using a lookup table containing values ​​determined during the calibration process, or values ​​derived therefrom, or using one or more mathematical formulas with predefined parameters and / or coefficients that can be determined during the calibration process and encode essentially the same information as the lookup table.

[0049] In an embodiment, the digital value “Dout” is determined based on only the value of index1 (ie, the value Val1 ) or is determined based on only the value of index2 (ie, the value Val2 ).

[0050] In an embodiment, the control loop is configured to dynamically adjust the value Val1 so that a first event (at the first event, Vp crosses Vt1) substantially always occurs at a first predefined time (e.g., T1target), and so that a second event (at the second event, Vn crosses Vn1) substantially always occurs at a second predefined time (e.g., T2target), wherein T1target and T2target have a predefined relationship relative to the period Tperiod, for example, T1target = 50% of Tperiod, and T2target = 60% of Tperiod, but of course, other percentages may also be used.

[0051] The method may also include the following steps: i) providing a sensor or bridge circuit having two excitation nodes (e.g., E1, E2) and at least one output node (e.g., RO1, RO2), such as a Hall element, a horizontal Hall element, a vertical Hall element, or a Wheatstone bridge, or a resistor bridge including at least one or at least two branches, each branch including at least two resistors (e.g., piezoresistors or magnetoresistive resistors), such as XMR, GMR, TMR, AMR.

[0052] The method may further include: providing one or more of the following: a timer, a counter operating at a predefined clock frequency (e.g., fCLK), a bias circuit (e.g., a variable voltage source or a variable current source), one or more comparators, an analog-to-digital converter (ADC), a digital-to-analog converter (DAC), a PWM circuit, a low-pass filter following the PWM circuit, and a lookup table with an index.

[0053] The method may also include the steps of: providing at least one comparator (e.g., one comparator or two comparators); and providing at least one threshold voltage (e.g., Vt) to a first input of at least one comparator; and providing at least one read voltage (e.g., Vp, Vn) to a second input of at least one comparator. In this case, the first event may be detected, for example, by monitoring when the output level of the comparator changes state.

[0054] The method may further include the following steps: providing at least one analog-to-digital converter (ADC); and step a) may further include: using the ADC to repeatedly digitize the at least one output voltage or the differential voltage formed by the two output voltages; and step b) may further include: (for example, by a comparison device (for example, by a programmable controller)) repeatedly comparing the multiple digital values ​​with at least one threshold.

[0055] In an embodiment, at least steps b) and c) are performed by a programmable controller, for example by a programmable digital processor.The controller may or may not be integrated in the same semiconductor substrate as the sensor circuit or the bridge circuit.

[0056] In a preferred embodiment, step c) comprises detecting when the sense voltage or the common mode voltage exceeds an associated threshold voltage by generating an interrupt signal when the output level of at least one comparator changes.Using interrupts avoids the use of a polling routine and is more power efficient.

[0057] In an embodiment, the bias signal of step a) has a waveform with a linearly increasing portion or a linearly decreasing portion; (also referred to as a "ramp"). The ramp may have a configurable slope and / or a configurable offset).

[0058] In an embodiment, the bias signal of step a) has a waveform with an exponential portion; (eg, such as may be generated by an RC circuit)

[0059] In an embodiment, the bias signal of step a) has a sinusoidal waveform.

[0060] In an embodiment, the method further includes the following steps: measuring temperature; and the method further includes the following steps: adjusting at least one threshold voltage based on the measured temperature, or adjusting at least one of the following items: a first time value (e.g., T1), a second time value (e.g., T2), a first count value (e.g., N1), a second count value (e.g., N2), a first index value (e.g., index1), a second index value (e.g., index2), a time difference (e.g., ΔT), a count difference (e.g., ΔN), an index difference (e.g., Δindex), a digital value based on the measured temperature (e.g., Dout).

[0061] In an embodiment, the sensor is or comprises at least one Hall element; (eg, a horizontal Hall element or a vertical Hall element).

[0062] In an embodiment, the bridge circuit is or includes at least one Wheatstone bridge. The Wheatstone bridge may include four resistors, which include one or more MR elements (e.g., AMR, TMR, GMR, XMR). The Wheatstone bridge may include four resistors, which include one or more piezoresistive elements.

[0063] In an embodiment, the bridge circuit comprises a plurality of branches, and wherein each branch comprises at least two resistors.

[0064] In an embodiment, the bridge circuit comprises a plurality of branches, and wherein each branch comprises at least two resistors.

[0065] According to a second aspect, the present invention also provides a circuit (e.g., a "sensing and digitizing circuit") for providing a digital value (e.g., Dout), which indicates a physical quantity to be measured by a sensor or a bridge circuit, the sensor or bridge circuit having two excitation nodes (e.g., E1, E2) and at least one readout node (e.g., RO1, RO2), the circuit comprising: a bias circuit; (preferably, the bias signal is applied to all sensors simultaneously); a threshold generator for generating at least one threshold signal or value; at least one of the following: a timer, a counter, a lookup table with a DAC; a comparison device (for comparing at least one readout voltage (e.g., Vp), or a signal or value derived therefrom, with at least one threshold signal or value; a controller configured to perform a method according to any aspect of the first aspect.

[0066] In embodiments where the sensor or bridge circuit has two readout nodes, the "circuit" may also be referred to as "circuit for digitizing the differential output signal of the sensor or bridge circuit."

[0067] Note that the threshold signal can be an analog signal (eg, a threshold voltage), or

[0068] According to a third aspect, the present invention also provides an integrated sensor device, comprising: at least one sensor or a bridge circuit having two excitation nodes (e.g., E1, E2) and at least one readout node (e.g., RO1, RO2); and at least one circuit according to the second aspect, which is operably connected to the excitation nodes and at least one readout node of the at least one sensor or bridge circuit.

[0069] In an embodiment, the integrated sensor device is a pressure sensor device and comprises at least one Wheatstone bridge comprising a plurality of piezoresistive elements.

[0070] In an embodiment, the integrated sensor device is a magnetic sensor device and comprises at least one Wheatstone bridge comprising a plurality of magnetoresistive elements (eg AMR, GMR, XMR, TMR).

[0071] In an embodiment, the integrated sensor device is a magnetic sensor device and comprises at least one horizontal Hall element and / or at least one vertical Hall element.

[0072] In an embodiment, the integrated sensor device comprises a plurality of at least two sensors or a bridge circuit.

[0073] In an embodiment, the integrated sensor device is a linear or angular position sensor device, a proximity sensor, a current sensor, or a torque sensor. In this case, the circuit can be further configured to output a digital value, or a value derived therefrom (e.g., a linear or angular position, a current value, a torque value).

[0074] In an embodiment, the integrated sensor device further includes one or two comparators, or three comparators (e.g., one for v1 or vp, one for v2 or vn, and one for Vcm) for each sensor or bridge circuit; wherein the output of each comparator is connected to a corresponding input of the controller.

[0075] Preferably, an input of the controller is configured to generate an interrupt to the controller, and preferably the controller has an interrupt routine for storing a time value or a counter value when an interrupt occurs.

[0076] In an embodiment, only one of the readout nodes is used, for example, because the second time value or count value or index value is based on a reference time or reference count, or because the common mode signal is derived from the bias signal. In this case, a single comparator can be used per sensor or per bridge circuit.

[0077] In an embodiment, two readout nodes are used, for example, because the second time value or count value or index value is based on a second event, wherein the second readout signal or value exceeds a threshold value. In this case, two comparators may be used per sensor or per bridge circuit.

[0078] In an embodiment, a circuit (e.g., a "sensing and digitizing circuit") is configured to provide a first digital value (e.g., Dout1); and the integrated sensor device further includes an analog-to-digital converter (e.g., ADC) configured to digitize one or both of the read voltages (e.g., Vp, Vn), or to digitize a differential voltage (e.g., Vdiff) formed by two read nodes (e.g., RO1, RO2), and to provide a second digital value (e.g., Dout2); and the sensor device is further configured to provide the first digital value and the second digital value (e.g., Dout1, Dout2) to allow an external controller to perform a consistency test, or is further configured to perform a consistency test of the first digital value and the second digital value (e.g., Dout1, Dout2), and to provide at least one of the following: the first digital value and the second digital value, or digital values ​​derived therefrom, and an error signal.

[0079] In other words, the integrated sensor device is configured to perform Fig.14 At least steps (i) and (ii) of the method illustrated in FIG.

[0080] According to a fourth aspect, the present invention also provides a method for providing a digital value (e.g., Dout) indicating a physical quantity to be measured by a sensor or a bridge circuit, the sensor or the bridge circuit having two excitation nodes (e.g., E1, E2) and at least one output node (e.g., RO1, RO2) (e.g., two readout nodes), the method comprising the following steps: a) applying a bias signal (e.g., Vbias) (e.g., a bias voltage or a bias current) to the excitation nodes (e.g., E1, E2) so that at least one output node (e.g., RO1, RO2) provides at least one output signal (e.g., Vp, Vn) (e.g., an output voltage or an output current); and applying a threshold signal (e.g., Vt), at least one of the bias signal and the threshold signal is a time-varying signal; b) determining at least one time value (e.g., T1) or at least one count value (e.g., N1) or at least one index value (e.g., index1) associated with a first event (e.g., event1), at which time at least one readout signal (e.g., Vp) exceeds at least one threshold signal (e.g., Vt); c) determining a digital value (e.g., Dout) indicating a physical quantity to be measured based on the at least one time value (e.g., T1) or the at least one count value (e.g., N1) or the at least one index value (e.g., index1).

[0081] In an embodiment, the method comprises applying a time varying bias signal and a time varying threshold signal.

[0082] In an embodiment, the method comprises applying a constant bias signal and a time varying threshold signal.

[0083] According to a fifth aspect, the present invention also provides a method for providing a digital value (e.g., Dout) indicating a physical quantity to be measured by a sensor or a bridge circuit, the sensor or the bridge circuit having two excitation nodes (e.g., E1, E2) and at least one output node (e.g., RO1, RO2) (e.g., two readout nodes), the method comprising the following steps: a) applying a time-varying bias signal (e.g., Vbias) (e.g., a bias voltage or a bias current) to the excitation nodes (e.g., E1, E2), so that at least one output node (e.g., RO1, RO2) provides at least one time-varying output signal (e.g., Vp, Vn) (e.g., Vp, Vn) , output voltage or output current); b) determining at least one time value (e.g., T1) or at least one count value (e.g., N1) or at least one index value (e.g., index1) associated with a first event (e.g., event1), at which first event (e.g., event1), at least one readout signal (e.g., Vp) exceeds at least one threshold signal (e.g., Vt); c) determining a digital value (e.g., Dout) indicating a physical quantity to be measured based on the at least one time value (e.g., T1) or the at least one count value (e.g., N1) or the at least one index value (e.g., index1).

[0084] In an embodiment, step b) includes: determining a first time value (e.g., T1) or a first count value (e.g., N1) or a first index value (e.g., index1) associated with a first event (e.g., event1), at which the first output signal (e.g., Vp) exceeds a first threshold signal (e.g., Vt, Vt1); and determining a second time value (e.g., T2) or a second count value (e.g., N2) or a second index value (e.g., index2) associated with a second event (e.g., event2), at which the second output signal (e.g., Vn) exceeds a second threshold signal (e.g., Vt1). t, Vt2), the second threshold signal (e.g., Vt, Vt2) is equal to or different from the first threshold signal; and step c) includes: determining a digital value (e.g., Dout) indicating a physical quantity to be measured by the sensor or bridge circuit based on the first time value and the second time value (e.g., T1, T2), or based on the first count value and the second count value (e.g., N1, N2), or based on the first index value and the second index value (e.g., index1, index2), or based on the difference (ΔT) between the first time value and the second time value, or based on the difference (ΔN) between the first count value and the second count value, or based on the difference (Δindex) between the first index value and the second index value.

[0085] Particular and preferred aspects of the invention are set out in the accompanying independent and dependent claims. Features from the dependent claims may be combined with features of the independent claims and with features of other dependent claims as appropriate, and not merely as explicitly set out in the claims. These and other aspects of the invention will be apparent from and elucidated with reference to the embodiment(s) described hereinafter. BRIEF DESCRIPTION OF THE DRAWINGS

[0086] Figure 1 A schematic block diagram of a horizontal Hall element is shown.

[0087] Figure 2A A schematic block diagram of a Wheatstone bridge comprising four resistors is shown.

[0088] Figure 2B A schematic block diagram of a bridge circuit with three branches (also called a "half-bridge"), each branch comprising three resistors, is shown.

[0089] Figure 3 shows a method for performing a differential voltage signal such as Figure 1 The sensor circuit or from Figure 2A A schematic block diagram of a circuit for digitizing a differential output voltage obtained by a bridge circuit.

[0090] Figure 4 An abstract high-level block diagram of the digitization circuit and integrated sensor device proposed by the present invention is shown.

[0091] Figures 5 to 9 Illustrative examples of graphs are shown, each graph showing a time-varying bias signal, one or two readout signals and one or two threshold signals, which may be used to illustrate the basic principles of the invention.

[0092] Figures 10 to 14 A flow chart of the method proposed by the present invention is shown.

[0093] Figures 15 to 17 A high-level block diagram of the circuits and devices proposed by the present invention is shown.

[0094] Fig.18 A digitization scheme with two parts (which can be represented by Fig.14 by means of and / or by Fig.17 An illustrative example of a graph of circuit usage).

[0095] These drawings are only schematic and non-limiting. In the drawings, for illustrative purposes, the size of some of the elements may be exaggerated and not drawn to scale. Any reference numerals in the claims should not be construed as limiting the scope. In different drawings, the same or similar reference numerals may refer to the same or similar elements. DETAILED DESCRIPTION

[0096] The present invention will be described with respect to specific embodiments and with reference to certain drawings, but the invention is not limited thereto but only by the claims. The drawings described are only schematic and non-limiting. In the drawings, for illustrative purposes, the size of some of the elements may be exaggerated and not drawn to scale. The dimensions and relative dimensions do not correspond to actual reductions in the practice of the invention.

[0097] Furthermore, the terms first, second, etc. in the specification and in the claims are used to distinguish between similar elements and are not necessarily used to describe a sequence in time, space, in ranking, or in any other manner. It should be understood that the terms so used are interchangeable under appropriate circumstances, and that the embodiments of the invention described herein are capable of operation in a sequence different from that described or illustrated herein.

[0098] Furthermore, the terms top, bottom, etc. in the description and claims are used for descriptive purposes and not necessarily for describing relative positions. It is to be understood that the terms so used are interchangeable under appropriate circumstances and that the embodiments of the invention described herein are capable of operation in orientations other than those described or illustrated herein.

[0099] It should be noted that the term "comprising" used in the claims should not be interpreted as being limited to the means listed thereafter; it does not exclude other elements or steps. Thus, the term should be interpreted as specifying the presence of the stated features, integers, steps or components as mentioned, but does not exclude the presence or addition of one or more other features, integers, steps or components, or groups thereof. Thus, the scope of the expression "a device comprising means A and B" should not be limited to devices consisting only of components A and B. It means that for the present invention, the only relevant components of the device are A and B.

[0100] References throughout this specification to "one embodiment" or "an embodiment" mean that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the invention. Thus, the appearances of the phrases "in one embodiment" or "in an embodiment" in various places throughout this specification do not necessarily all refer to the same embodiment, but may. Furthermore, in one or more embodiments, as would be apparent to one of ordinary skill in the art from this disclosure, the particular features, structures, or characteristics may be combined in any suitable manner.

[0101] Similarly, it should be appreciated that in the description of exemplary embodiments of the invention, for the purpose of streamlining the disclosure and aiding in the understanding of one or more of the various inventive aspects, the various features of the invention are sometimes grouped together in a single embodiment, figure, or description thereof. However, this method of disclosure should not be interpreted as reflecting an intention that the claimed invention requires more features than those explicitly recited in each claim. On the contrary, as reflected in the appended claims, the inventive aspects lie in fewer features than all of the features of a single preceding disclosed embodiment. Thus, the claims appended to the Detailed Description are hereby expressly incorporated into the Detailed Description, with each claim itself representing a separate embodiment of the invention.

[0102] In addition, although some embodiments described herein include some features included in other embodiments but do not include other features included in these other embodiments, the combination of features of different embodiments is intended to fall within the scope of the present invention and form different embodiments as will be understood by those skilled in the art. For example, in the appended claims, any of the embodiments claimed for protection may be used in any combination.

[0103] In the description provided herein, numerous specific details are set forth. However, it should be understood that embodiments of the present invention may be implemented without these specific details. In other examples, well-known methods, structures, and techniques are not shown in detail to avoid confusion in understanding this description.

[0104] In this document, the terms "count value" and "counter value" mean the same thing. The counter may be configured to be incremented by 1 or decremented by 1, but the present invention is not limited thereto.

[0105] The present invention generally relates to methods and circuits for providing a digital value (e.g., Dout) indicating a physical quantity to be measured by a sensor circuit (e.g., a magnetic field value or a pressure value), and more specifically, to methods and circuits for digitizing an output signal (e.g., a differential output signal vdiff) of a sensor circuit or a bridge circuit of the type having two excitation nodes (also referred to as "input nodes") and at least one (e.g., two) readout nodes (also referred to as "output nodes").

[0106] Figure 1 An example of such a sensor circuit (i.e., a horizontal Hall element 140) is shown, but the present invention is not limited thereto and works equally well for, for example, a vertical Hall element. When a bias signal (e.g., a bias voltage or a bias current) is applied to the Hall element, a differential signal (e.g., an output voltage or an output current) indicating the magnetic field characteristics will appear on the output node. However, the voltage between nodes RO1 and E2 can be regarded as another differential voltage, and the voltage between nodes RO2 and E2 can be regarded as another differential voltage.

[0107] Figure 2A An example of a bridge circuit 240 is shown, namely a Wheatstone bridge including four resistors R1, R2, R3, R4. The resistors may be, for example, piezoresistors formed on a silicon film for measuring pressure, or may be magnetoresistive (MR) elements (e.g., GMR, XMR, TMR, AMR elements) indicating magnetic field characteristics, but the present invention is not limited to a full-bridge circuit with two branches (each with a readout node), but works equally well for one or more half-bridges, each with one or more readout nodes, such as Figure 2B , a bridge circuit with three branches (each branch having three resistors and two sense nodes) is shown. Many differential voltages can be obtained from this circuit (e.g., between sense nodes RO1 and RO3, or between nodes RO3 and RO5, or between nodes RO3 and RO6, or between nodes RO2 and E2), just to name a few.

[0108] Figure 3 A classic circuit for sensing and digitizing a differential voltage signal Vdiff is shown. The differential voltage signal Vdiff is obtained, for example, from Figure 1 The horizontal Hall element shown in FIG. 1 is obtained, or from a vertical Hall element (not shown), or from Figure 2A The Wheatstone bridge shown in FIG. 1 is obtained, or from Figure 2B, or from another sensor circuit or bridge circuit having at least two excitation nodes E1, E2 and at least one output node RO1. As described above, the differential voltage can be obtained between two read nodes (e.g., RO1, RO2), but can also be obtained between a read node (e.g., RO1) and an excitation node (e.g., E2). Figure 3 The classical sensing and digitizing circuits have been discussed in the background section and are well known in the art.

[0109] Figure 4 An abstract high-level block diagram of a sensor or bridge 440, and a digitizing circuit 420 operatively connected to the sensor or bridge 440, is shown, the sensor or bridge 440 having two input nodes E1, E2 and two output nodes RO1, RO2. It can be seen that the digitizing circuit 420 is configured to provide a bias signal (e.g., a bias voltage or a bias current) to the input nodes E1, E2 of the sensor or bridge, and is configured to receive at least one output voltage (e.g., two output voltages v1, v2) from the sensor or bridge. Depending on the specific implementation, the digitizing circuit 420 may treat, for example, the signals V1 and V2 as differential voltage signals to be digitized, or may treat the signals V1 and "Vbias-(Vbias-)" as differential voltages. The digitizing circuit 420 is configured to convert the differential voltage signal into a digital value, which process may also be referred to as "digitizing" the differential voltage signal, or in fact, digitizing the measured physical signal (such as, for example, a magnetic field, pressure, etc.).

[0110] Figure 4 An integrated sensor device 430 is also shown, comprising such a sensor or bridge 440 and such a digitizing circuit 420 .

[0111] In a variation, the digitizing circuit 420 does not provide a differential bias voltage formed by Vbias+ and Vbias- to the first input node E1, but instead provides a "single-ended" bias voltage Vbias to the first input node E1, while the second input node E2 is connected to a reference voltage (commonly referred to as Vss or Gnd).

[0112] In another or further variation, the digitizing circuit 420 provides a bias current instead of a bias voltage. The bias current may be provided by a "current source".

[0113] Figures 5 to 9 and Fig.14Various illustrative examples are shown of graphs showing one or more of the following signals: a bias signal Vbias, one or two readout signals Vp and Vn, at least one threshold signal Vt, a common mode signal Vcm, some or all of which may be used in embodiments of the present invention.

[0114] Figure 5 Illustrative examples of graphs that may be used to illustrate certain principles that may be used in embodiments of the invention are shown.

[0115] Figure 5 The graph shows a plurality of curves, including a time-varying bias voltage signal Vbias, Figure 5 In the example of FIG. 1 , the time-varying bias voltage signal Vbias increases linearly over time from a first value Vmin at time T_start to a second value Vmax at time T_end. When the time-varying bias voltage Vbias(t) is applied to Figure 4 When the first input node E1 of the sensor or bridge 440 is applied, the output nodes RO1 and RO2 will provide two time-varying signals v1 and v2, which together form a time-varying differential output voltage vdiff. In practice, the voltage level of v1 may be greater than the voltage level of v2, for example depending on whether the measured magnetic field is positive or negative, or for example depending on whether the resistance of the (one or more) variable resistors of the bridge is less than or greater than the resistance of the other resistors. In order to simplify the drawings, v1 and v2 are not shown, but Vp and Vn are shown, where Vp represents the output signal with a "higher" voltage level and Vn represents the output signal with a "lower" voltage level.

[0116] Figure 5 Also shown is a common mode signal Vcm, which in this example is defined as the average of the output voltages v1 and v2, or as the average of Vp and Vn. This can be written mathematically as: Vcm = (Vn + Vp) / 2. The signal Vp can then also be written as Vp = Vcm + (Vdiff / 2), and the signal Vn can then also be written as Vn = Vcm - (Vdiff / 2). Note that in some embodiments (see, for example, Figure 6B ), the common-mode signal Vcm may optionally be explicitly generated, for example, by summing the output signals (e.g., using an operational amplifier) ​​and by dividing the result by 2 (e.g., using a voltage divider comprising two resistors connected in series), or in any other suitable manner.

[0117] In an embodiment, the signal Vcm is derived directly from Vbias, for example via a voltage divider comprising two resistors connected in series. The value of Vcm may be a predefined part or fraction (eg 50%) of Vbias. The value of the part may be defined by the resistor value.

[0118] Figure 5 Also shown is the threshold voltage Vt, Figure 5 In the example of , the threshold voltage Vt has a predefined constant value that does not change during the time interval and does not change within a plurality of time intervals ( Figure 5 Only one time interval is shown in FIG. 1 ). However, the present invention is not limited thereto, and in other embodiments, the threshold voltage Vt may have a predefined waveform that changes within one time interval (e.g., as a linear decreasing function), or remain constant during the time interval but may have another constant value during a subsequent time interval.

[0119] In certain embodiments of the present invention, the value of the threshold voltage Vt is constant in principle, but is temperature compensated.

[0120] As in Figure 5 In the example of , it can be seen that the signal Vp exceeds the threshold voltage Vt at time T1 (defining the first event), and the signal Vn exceeds the threshold voltage at time T2 (defining the second event). The times T1 and T2 can be determined, for example, using a timer (e.g., implemented in a digital processor), or measured using a counter operating at a predefined clock frequency fCLK.

[0121] However, in the prior art, a quiescent bias voltage equal to Vmax is applied to the first input node E1 of the sensor or bridge, and the signals Vn and Vp are routed to an amplifier, and the differential output voltage is digitized (e.g., as Figure 3 ), the inventors of the present invention will appreciate that the value of Vdiff indicative of (e.g., proportional to) the physical quantity to be measured (e.g., magnetic field component value, pressure value, etc.) can also be derived (e.g., by considering one or more of the following values: Vmin, Vt, Vmax, T_ramp), for example, from the times T1 and T2 and the bias signal Vbias and the threshold signal Vt. This can be mathematically written as:

[0122] Dout = f1(T1, T2, waveform of bias signal, Vt)[1], or written as:

[0123] Dout = f2(T2-T1, waveform of bias signal, Vt)[2], or written as:

[0124] Dout = f3 (N1, N2, waveform of bias signal, Vt) [3], or written as:

[0125] Dout = f4 (N2-N1, waveform of bias signal, Vt) [4]

[0126] Where T1 is the time of event1, and T2 is the time of event2,

[0127] Where (T2-T1) = ΔT is the time difference between the first event and the second event, or as:

[0128] Wherein, N1 is a first count value associated with event1, and N2 is a second count value associated with event2,

[0129] Where (N2-N1) = ΔN is the count difference between the first event and the second event,

[0130] Wherein, the Vbias waveform may be represented by a set of parameters such as Vmin, Tstart, Vmax, Tend, or by a set of parameters Vmin, Vmax, slope;

[0131] Or if the bias signal is generated using a DAC and an index table (e.g. stored in non-volatile memory):

[0132] Dout = f5(index1, index2, Vt)[5], or written as:

[0133] Dout=f6(index2-index1,Vt)[6]

[0134] In some embodiments, the waveform of the bias signal Vbias is fixed (e.g., hard-coded in software, or generated by a hardware circuit in a predetermined manner), and the value of the threshold voltage Vt (e.g., a predefined voltage level) is also fixed. In such cases, there is a one-to-one correspondence between the amplitude of the physical quantity to be measured (e.g., a magnetic field value or a pressure value) and the timing of the first event (at the first event, Vp crosses Vt), and the timing of the second event (at the second event, Vn crosses Vt). This relationship can be determined, for example, during a calibration test, and the result can be stored in a lookup table. It can be said that the values ​​of the lookup table implicitly take into account the details of the bias signal and the threshold signal. Note that the waveform of Vbias and / or the waveform of the threshold signal Vt do not need to be known. With this lookup table, the digital output value can then be determined as:

[0135] Dout=LookupTable7[T2-T1](Dout=LookupTable7[T2-T1])[7], or determined as:

[0136] Dout=LookupTable8[N2-N1](Dout=LookupTable8[N2-N1])[8], or determined as:

[0137] Dout = LookupTable9[index2-index1] [9]

[0139] The values ​​of the lookup table may be stored in a non-volatile memory of the sensor device (see e.g. Fig.17 ), and linear interpolation can be applied during retrieval.

[0140] Note that (T2-T1) can also be written as ΔT, so that the lookup table can be a one-dimensional table. Similarly, (N2-N1)=ΔN, (Index2-Index1)=ΔIndex.

[0141] It is also possible to express Dout as a polynomial expression of a single value (T2-T1)=ΔT or a polynomial expression of a single value (N2-N1)=ΔN or a polynomial expression of a single value (Index2-Index1)=ΔIndex using a plurality of coefficients that may be determined during the calibration process and may be stored in a non-volatile memory of the sensor device. It can be said that the values ​​of the coefficients implicitly take into account the details of the bias signal and the threshold signal. Note that the waveform of Vbias and / or the waveform of the threshold signal Vt do not need to be known. By means of the polynomial, the digital output value can then be determined as:

[0142] Dout = Polynomial10(T2-T1)(Dout = Polynomial10(T2-T1))

[10] , or as

[0143] Dout = Polynomial11(N2-N1)(Dout = Polynomial11(N2-N1))

[11] , or as

[0144] Dout = Polynomial12 (index2 - index1) (Dout = Polynomial12 (index2 - index1))

[12]

[0145] Note that (T2-T1) = ΔT is a single value, so Polynomial10 is a function of a single variable ΔT. The same is true for Polynomial11 and Polynomial12.

[0146] The coefficients of these polynomials may be determined during calibration testing, using the same bias signal Vbias and the same threshold signal Vt as will be used during actual use.

[0147] Of course, it is also possible to express Dout as a polynomial expression of two variables (T1, T2) or (N1, N2) or (Index1, Index2) using multiple coefficients, where the values ​​of the coefficients take into account the details of the bias signal and the threshold signal. This can be written as:

[0148] Dout = Polynomial13(T1, T2)

[13] , or written as

[0149] Dout = Polynomial14(N1, N2)

[14] , or written as

[0150] Dout=Polynomial15(index1,index2)

[15]

[0151] So far, the description Figure 5 How to illustrate the method of determining a digital value Dout, which indicates the Figure 1 or Figure 2A The physical quantity measured by the sensor circuit 140 or the bridge circuit 240 with two output nodes shown in the figure can be determined based on the value ΔT or ΔN or Δindex corresponding to the time difference (T2-T1) or the count difference (N2-N1) or the index difference (index1-index2) between the first event (event1) and the second event (event2). At the first event (event1), the first output signal Vp exceeds the threshold signal Vt, and at the second event (event2), the second output signal Vn exceeds the same threshold signal Vt, but this is not the only possible way how the physical quantity sensed by the sensor circuit 140 or the bridge circuit 240 can be measured.

[0152] In fact, if the waveform of Vbias as a function of time (e.g., a predefined ramp waveform) is known, then the waveform of the common mode voltage Vcm corresponding to the average of Vp and Vn is also known (explicitly or implicitly), which is also substantially equal to 50% of Vbias. And if the value of the threshold signal Vt (e.g., a predefined constant voltage level, or a predefined fraction of Vmax) or the waveform of Vt as a function of time is known, then the time Tcm at which the waveform Vcm passes through Vt is also known (explicitly or implicitly). It is also possible to measure only T1, rather than measuring T1 for event1 (when Vp exceeds Vt) and measuring T2 for event2 (when Vn exceeds Vt), because the time T2 at which Vn will pass through Vt is related to the time between T1 and Tcm. In other words, (Tcm-T1) and (T2-Tcm) are related to each other.

[0153] Thus, if the relationship between Vcm and Vbias is known, and if the relationship between Vt and Vmax (i.e. the maximum value of Vbias) is known, the value of Vdiff and thus the value of the physical quantity can be determined as a function of a single time T1. This can be written mathematically as:

[0154] Dout = f16 (T1, waveform of bias signal, Vt)

[16]

[0155] Dout = f17 (N1, waveform of bias signal, Vt)

[17]

[0156] Wherein, the Vbias waveform may be represented by a set of parameters such as, for example, Vmin, Tstart, Vmax, and Tend, or by a set of parameters Vmin, Vmax, and slope;

[0157] Or if the bias signal is generated using a DAC and an index table (e.g. stored in non-volatile memory):

[0158] Dout=f18(index1,Vt)

[18]

[0159] As already mentioned above, in practice, the bias signal Vbias may have a predefined waveform (e.g., a linearly increasing ramp), and the threshold signal may also have a predefined waveform (e.g., a linearly decreasing function, or a predefined constant value), and the bias signal and the threshold signal are reused in each measurement cycle. In such a case, there is a one-to-one correspondence between the physical quantity to be measured and the (single) time value T1 associated with the first event, or the single count value N1, or the single index value Index1; this relationship may be determined during a calibration test, and this relationship may be stored in a non-volatile memory, for example, in the form of a lookup table, in the form of a polynomial expression, or in any other suitable manner.

[0160] When using a lookup table that takes into account the details of the bias signal and the threshold signal, the digital output value can be determined as:

[0161] Dout = LookupTable19[T1]

[19] , or is determined to be

[0162] Dout = LookupTable20[N1]

[20] , or is determined as

[0163] Dout=LookupTable21[index1]

[21]

[0164] It is also possible to use multiple coefficients to represent Dout as a single value (T1) or a single count value (N1) or a single index value (index1) as a polynomial expression, where the values ​​of the coefficients take into account the details of the bias signal and the threshold signal. This can be written as:

[0165] Dout = Polynomial22(T1)

[22] , or written as

[0166] Dout = Polynomial23(N1)

[23] , or written as

[0167] Dout=Polynomial24(index1)

[24]

[0168] Methods for determining a digital value indicating the magnitude of a physical quantity to be measured (e.g., magnetic field strength, pressure) based on these principles are as follows: Fig.10 shown.

[0169] Note that the Figure 5 for illustrating the basic principle of the invention, which is particularly useful for a Hall element or for a Wheatstone bridge (where Vp and Vn have a symmetrical behavior with respect to the common mode voltage Vcm), but the invention is not limited thereto, and Figure 5The same principles explained in can also be used, for example, to determine the digital value of a physical quantity measured by a circuit having only one output node, such as a circuit consisting of two resistors in series (e.g. two piezoresistors or two magnetoresistive resistors), where one or both resistor values ​​vary depending on the external physical quantity to be measured, which can be viewed as Figure 2B A special case of a resistor circuit. Such a circuit also has two excitation nodes E1, E2 and an output node (a node between the two resistors), and when a bias signal Vbias is applied to the excitation nodes, a single output signal will be provided. Depending on the physical quantity to be measured, the moment T1 at which the output signal crosses the threshold voltage will change. In other words, also in this case, when the bias signal Vbias has a predefined waveform (e.g., a linearly increasing function), and when the threshold signal Vt has a predefined waveform or a predefined value, there will be a one-to-one correspondence between the time T1 (or count N1, or index Index1) at which the output signal crosses the threshold voltage. This relationship between the physical quantity and T1 can be determined during a calibration process and can be stored in a non-volatile memory, for example, in the form of a lookup table or in the form of a set of coefficients of a polynomial equation. Then, the value of Dout can also be determined using formulas

[19] to

[24] . Note that Figure 5 The curve of can also be used to understand how this method will work for a circuit with only two resistors but where there will be only one output signal (eg, Vp).

[0170] Those skilled in the art who have benefited from the present disclosure will also appreciate that the above measurement principle (the above measurement principle of applying the time-varying signal Vbias, and using a constant or time-varying threshold signal Vt, and measuring the time T1 or count N1 of the first event (at the first event, the node voltage exceeds the threshold signal Vt) in order to obtain the digital value of the external quantity to be measured) can also be applied to Figure 2B For each node of interest, the corresponding lookup table, and / or the coefficients of the polynomial function can be determined during the calibration process and can be stored in a non-volatile memory of the sensor device. The lookup table or these coefficients can then be used later (during actual use of the sensor device) to convert the measured time value T1 or count value N1 or index value Index1 into a digital value of the physical quantity to be measured.

[0171] exist Figure 5 In another or further variation (not shown), the sensor circuit may apply one of a plurality of possible bias signals, such as a first bias signal having a first predefined waveform that increases linearly (see Figure 5) or a second bias signal having an exponentially increasing second predefined waveform. In this case, two (or more) lookup tables and / or two (or more) polynomial functions may be determined during calibration testing and during actual use of the sensor device, and appropriate lookup tables or polynomial functions need to be selected. Or in other words, in order to determine the output value, an additional parameter is needed, i.e., a value for indicating which of the predefined bias signals is used.

[0172] In another or further variation (for example, as will be Fig. 8A and Figure 8B ), the sensor circuit may have two output nodes (e.g., Vp and Vn), and the method may use a single predefined threshold signal (Vt) for two events (event1 and event2), or may use a first predefined threshold signal (Vt1) for the first event and a second predefined threshold signal (Vt2) for the second event. Also in this case, two lookup tables and / or two polynomial functions may be determined during calibration testing and during actual use of the sensor device, and the appropriate lookup table or polynomial function needs to be selected. Or in other words, in order to determine the output value, an additional parameter is needed, namely a value for indicating which of the predefined bias signals is used.

[0173] It is also possible to use one of several possible bias signals and one of several possible threshold signals. In this case, two additional parameters are required to determine the digital output value: a first parameter for indicating a suitable bias signal; and a second parameter for indicating a suitable threshold signal.

[0174] Reference FIG. 6A to FIG. 9 and Fig.14 These and other variations of the method are further described and illustrated, but before doing so, a description will be given of Figure 5 Some other considerations.

[0175] exist Figure 5 In the example of , the bias signal is a ramp with a predefined slope, starting from a value Vmin equal to zero, but this is not absolutely necessary and the ramp may also start from a non-zero (eg predefined) value.

[0176] exist Figure 5 In the example of , the ramp increases over time (ie has a positive slope), but it is also possible to use a ramp with a negative slope.

[0177] In some embodiments, a first event may be detected using a first comparator having a threshold voltage Vt as a reference input and a signal Vp as a signal input, and a second event may be detected using a second comparator having a threshold voltage Vt as a reference input and a signal Vn as a signal input.

[0178] In embodiments where the sensor circuit (e.g., a resistor circuit having two resistors connected in series) has only one output node, a comparator can be used to detect the first event using the output voltage of the sensor circuit as an input signal for the comparator and the threshold voltage Vt as a reference signal for the comparator.

[0179] exist Figure 5 In the example of , the ramp is a continuous time and continuous value function (i.e., a "continuous ramp") (as can be generated, for example, using an operational amplifier), but the invention can also use a discrete time and discrete value function (i.e., a "discrete ramp") or a "stepped ramp" (also called a "staircase" function), where the amplitude of the bias signal changes in discrete steps at discrete moments, which can be generated, for example, by a digital processor with a DAC, or by a digital processor with a PWM module followed by a low pass filter (for reducing voltage ripple). The bias waveform can be generated using a counter or a lookup table or a memory, and the bias signal can be generated by changing the counter value or index value over time. An important advantage of this approach is that the detection of the first event (when Vp exceeds Vt) or the second event (when Vn exceeds Vt) boils down to determining the index value of the bias signal associated with these events, which index value is not dependent or less dependent on clock jitter, and thus the method becomes jitter-free. In addition, if Vt is derived from the same supply voltage that is also applied to the DAC or also applied to the digital processor, the index value will also be less sensitive to supply voltage changes. As mentioned above, the bias signal may be a voltage signal, or a current signal, or a charge signal. The ramp may be an increasing function or a decreasing function. The bias signal may be a periodic signal, but need not be a periodic signal that repeats every time period. The bias signal need not vary between a predefined value Vmin equal to zero and a predefined value Vmax, but may also employ other predefined waveforms.

[0180] The same methods and / or formulas as mentioned above may be used.

[0181] Fig. 6A Shows Figure 5A variation of a graph of , wherein the differential voltage signal of the sensor circuit 140 or the bridge circuit 240 is determined by measuring a time T1 or a counter value count1 corresponding to a first event, at which Vp exceeds a threshold voltage Vt, and by considering a time T2 or a counter value count2 corresponding to a second event, at which the common mode voltage Vcm (e.g., explicitly) exceeds or will (e.g., implicitly) exceed the threshold voltage Vt. Note that this time T2 or count value count2 is independent of the magnetic field (or pressure, or other physical quantity to be measured) and can be implemented as a predefined time (e.g., T2ref) or as a predefined count value (e.g., count2ref or N2 reference). As can be appreciated, since the signals Vcm and Vn are not explicitly used in this embodiment, the signal Vcm does not need to be actually available. In this case, the digital value of the physical quantity to be measured can be mathematically written as:

[0182] Dout = f25 (T1, T2ref, waveform of bias signal, Vt)

[25]

[0183] Dout = f26 (T2ref - T1, waveform of bias signal, Vt)

[26]

[0184] Dout = f27 (N1, N2ref, waveform of bias signal, Vt)

[27]

[0185] Dout = f28 (N2ref - N1, waveform of bias signal, Vt)

[28]

[0186] Wherein, the Vbias waveform may be represented by a set of parameters such as, for example, Vmin, Tstart, Vmax, Tend, or by a set of parameters Vmin, Vmax, slope;

[0187] Or if the bias signal is generated using a DAC and an index table (e.g. stored in non-volatile memory):

[0188] Dout=f29(index1, index2, Vt)

[29] , or written as:

[0189] Dout=f30(index2-index1,Vt)

[30]

[0190] Alternatively, in the case where the bias signal and / or the threshold signal have predefined, e.g., built-in waveforms, the specific shapes of these waveforms are not absolutely necessary for determining the output value, for the same reasons as described above, and the relationship between the physical quantity to be measured (e.g., the magnetic value of the pressure value) and the (one or more) instants at which the (one or more) output signals of the sensor circuit cross the (one or more) threshold signals Vt can be determined by calibration tests and can be stored in a non-volatile memory (e.g., in the form of a lookup table or polynomial expression). During actual use of the sensor device, the digital output value can then be determined as:

[0191] Dout = LookupTable26[T2ref-T1]

[31] , or determined as

[0192] Dout = LookupTable27[N2ref-N1]

[32] , or is determined as

[0193] Dout=LookupTable28[index2-index1]

[33]

[0194] It is also possible to express Dout as a polynomial expression of a single value (T2ref-T1) or a polynomial expression of a single value (N2ref-N1) using multiple coefficients, where the values ​​of the coefficients take into account the details of the bias signal and the threshold signal. This can be written as:

[0195] Dout = Polynomial34(T2ref-T1)

[34] , or written as

[0196] Dout=Polynomial35(N2ref-N1)

[35]

[0197] Dout=Polynomial36(index2-index1)

[36]

[0198] It is also possible to express Dout as a polynomial expression of two variables (T1, T2) or (N1, N2) or (Index1, Index2) using multiple coefficients, where the values ​​of the coefficients take into account the details of the bias signal and the threshold signal. This can be written as:

[0199] Dout = Polynomial37(T1, T2)

[37] , or written as

[0200] Dout = Polynomial38(N1, N2)

[38] , or written as

[0201] Dout=Polynomial39(index1,index2)

[39]

[0202] Methods for determining digital values ​​based on these principles include Fig.11 shown.

[0203] Figure 6B Shows Fig. 6A 6 , but wherein the common mode signal Vcm is actually generated, and wherein the time T2 of the second event or the count value count2 is actually determined as the moment when the signal Vcm actually exceeds the threshold voltage Vt. In a preferred embodiment, the second event is detected using a second comparator having the threshold voltage Vt as a reference input and the signal Vcm as a signal input.

[0204] The value of Dout can be determined using the following formula:

[0205] Dout = f40 (T1, T2, waveform of bias signal, Vt)

[40] , or determined as:

[0206] Dout = f41 (T2-T1, waveform of bias signal, Vt)

[41] , or determined as:

[0207] Dout = f42 (N1, N2, waveform of bias signal, Vt)

[42] , or determined as:

[0208] Dout=f43(N2-N1, waveform of bias signal, Vt)

[43] ,

[0209] Wherein, the Vbias waveform may be represented by a set of parameters such as, for example, Vmin, Tstart, Vmax, Tend, or by a set of parameters Vmin, Vmax, slope;

[0210] Or if the bias signal is generated using a DAC and an index table (e.g. stored in non-volatile memory):

[0211] Dout=f44(index1, index2, Vt)

[44] , or as:

[0212] Dout=f45(index2-index1,Vt)

[45]

[0213] In embodiments where the bias signal and the threshold signal have predefined waveforms or values, the specific shapes of the bias signal and the threshold signal need not be considered in the output function, but the digital output value may be determined as:

[0214] Dout = LookupTable46[T2-T1]

[46] , or determined as

[0215] Dout = LookupTable47[N2-N1]

[47] , or is determined as

[0216] Dout=LookupTable48[index2-index1]

[48]

[0217] It is also possible to express Dout as a polynomial expression of a single value (T2-T1) or a polynomial expression of a single value (N2-N1) or a polynomial expression of a single value (index2-index1) using multiple coefficients, where the values ​​of the coefficients take into account the details of the bias signal and the threshold signal. This can be written as:

[0218] Dout = Polynomial49(T2-T1)

[49] , or written as

[0219] Dout=Polynomial50(N2-N1)

[50]

[0220] Dout=Polynomial51(index2-index1)

[51]

[0221] It is also possible to express Dout as a polynomial expression of two variables (T1, T2) or (N1, N2) or (Index1, Index2) using multiple coefficients, where the values ​​of the coefficients take into account the details of the bias signal and the threshold signal. This can be written as:

[0222] Dout = Polynomial52(T1, T2)

[52] , or written as

[0223] Dout = Polynomial53(N1, N2)

[53] , or written as

[0224] Dout=Polynomial54(index1,index2)

[54]

[0225] Fig.13 A method of using these principles to determine a digital value indicative of a physical quantity to be measured and / or indicative of a differential output signal Vdiff that will appear at output nodes v1, v2 of a sensor or bridge circuit when a bias voltage Vbias reaches a predefined value Vmax is shown in FIG.

[0226] In an embodiment, signal Vcm is derived from Vp and Vn (eg by averaging these signals). The measured time of T2 or count N2 may be compared to a predetermined time or count value and an error signaled if the measured time deviates too much.

[0227] Figure 7 Shows Figure 5 A simple version of the invention, which is based on a first event event1 associated with a first time T1 or a first count value count1 and based on a second event event2 associated with a second time T2 or a second count value count2, at the first event event1, one of the output nodes (in the example: Vp) exceeds a threshold voltage Vt, and at the second event event2, the other output node (in the example: Vn) passes the same threshold voltage Vt. For example, the first event can be detected using a first comparator, using Vt as a first input and using Vp as a second input. For example, the second event event2 can be detected using a second comparator, using Vt as a first input and using Vn as a second input.

[0228] Fig.12 A method for determining a digital value indicating a physical quantity to be measured and / or indicating a differential output signal Vdiff that will appear at output nodes v1, v2 of a sensor or bridge circuit when a bias voltage Vbias is a predefined value Vmax is described in the specification.

[0229] Fig. 8A The diagram shows Figure 5 another variation of Figure 7 A further variant of wherein two different threshold signals are used: a first threshold voltage Vt_p and a second threshold voltage Vt_n, Vt_n being different from Vt_p. Fig. 8A In the example shown, Vt_p is higher than Vt_n, but this is not absolutely necessary. In the example shown, a first event event1 occurs when Vp exceeds Vt_p, and a second event occurs when Vn exceeds Vt_n.

[0230] The two reference voltages may have predefined (e.g. constant) voltage levels, or may be determined and set dynamically (e.g. at the beginning of each new time period). In the former case, only a single lookup table or polynomial expression is required for determining the digital output value. In the latter case, multiple lookup tables or multidimensional lookup tables, or multiple polynomial expressions, or polynomials with additional parameters may be required to take into account which threshold signals are applied during the measurement.

[0231] exist Fig. 8A A variant (not shown) (which can also be viewed as Figure 6B In a variant of ), a first event event1 occurs when Vp exceeds a first threshold voltage Vt1, and a second event occurs when Vcm exceeds a second threshold voltage Vt2 different from Vt1. Similar formulas to those mentioned above can be used.

[0232] exist Fig. 8A Another variant (not shown) (which can also be seen as Figure 6B In another variation of ), a first event event1 occurs when Vn exceeds a first threshold voltage Vt1, and a second event occurs when Vcm exceeds a second threshold voltage Vt2 different from Vt1. Similar formulas to those mentioned above can be used.

[0233] Figure 8B The diagram shows Figure 5 Another variant of (which can also be considered as Fig. 8A A further variant of , in which two threshold voltages are used: a first threshold voltage Vt1 and a second threshold voltage Vt2. A first event (event1) is defined as the moment when one of the signals (e.g., Vp) exceeds the first threshold Vt1, and a second event (event2) is defined as the moment when the same signal (e.g., Vp) exceeds the second threshold Vt2. Using a first lookup table or a first polynomial that takes into account Vbias and the first threshold Vt1, a first value Dout1 for Dout can be determined based on the time T1 or count N1 of the first event. And using a second lookup table or a second polynomial that takes into account the second threshold signal Vt2, a second value Dout2 for Dout can be determined based on the time T2 or count N2. If the physical quantity between the two events does not change significantly, the values ​​of Dout1 and Dout2 should be approximately the same. In an embodiment, the two values ​​Dout1 and Dout2 are averaged to increase the signal-to-noise ratio (SNR) of the measurement. In an embodiment, the consistency of the two values ​​Dout1 and Dout2 is tested and used as a diagnostic signal for detecting errors.

[0234] Figure 8C The diagram can be viewed as Fig. 8AA method of yet another variation of the present invention, in which two different threshold signals (i.e., Vtp and Vtn) are used, which are constant during each time slot but dynamically updated in different time slots. The first threshold signal Vtp is generated by digitizing the first digital value Val1, and the second threshold signal Vtn is generated by digitizing the second digital value Val2 (for example, by applying the first digital value Val1 and the second digital value Val2 to at least one DAC (digital-to-analog converter) and optionally using a sample and hold circuit). The first event occurs at time T1 at which the first signal Vp(t) exceeds the first threshold signal Vtp, and the second event occurs at time T2 at which the second signal Vn(t) exceeds the second threshold signal Vtn. Then, a closed-loop controller (for example, using a "PID control loop") is used to update the first digital value Val1 and the second digital value Val2 so that in the next time slot, the value of T1[k+1] will be approximately equal to the first target value T1target, and so that in the next time slot, the value of T2[k+1] will be approximately equal to the second target value T2target. In Figure 8C In , the threshold signals are labeled Vtp[k] and Vtn[k] to clearly indicate that they are updated in each new time slot ( Figure 8C Only one time slot is shown).

[0235] In an embodiment, the threshold Val1 (or Val1[k]) is dynamically updated so that the measured value of T1 or N1 at which Vp(t) crosses Vtp[k] is approximately equal to the first predefined target value T1target or N1target; and the threshold Val2 (or Val2[k]) is dynamically updated so that the measured value of T2 or N2 at which Vn(t) crosses Vtn[k] is approximately equal to the second predefined target value T2target or N2target, T2target or N2target being equal to, greater than or less than T1target or N1target.

[0236] exist Figure 8C In the example shown, T1target is selected equal to 50% of the period T_ramp and T2target is selected equal to 60% of the period T_ramp, but of course the invention is not limited thereto and other absolute or relative values ​​(eg as percentages of T_ramp) may also be used.

[0237] In an embodiment, the thresholds Val1 and Val2 are dynamically adjusted so that the measured (T2-T1)=ΔT is substantially equal to a predefined target value ΔTtarget.

[0238] Interestingly, if such a control loop is used, once the control loop is actively tracked (or "locked"), the digital value Dout of the physical quantity to be measured can be determined as a function of the values ​​Val1 and Val2 or as a function of (Val1-Val2). As mentioned above, the predefined function can be implemented as a lookup table or as a polynomial function, whose values ​​or coefficients can be determined by performing calibration tests and can be stored in a non-volatile memory, from which they can be retrieved during actual use of the sensor device.

[0239] Fig.8D Shows Figure 8C A special case of wherein the control loop is configured to dynamically update the thresholds Val1, Val2 such that the first event and the second event substantially coincide.

[0240] For a sensor circuit having two output signals Vp and Vn, the digital value of the physical quantity to be measured can be determined as a function of (Val1-Val2).

[0241] For sensor circuits having two output signals Vp and Vn having a predefined relationship with respect to each other (such is the case, for example, for Hall elements and Wheatstone bridges with MR elements), the digital value of the physical quantity to be measured can also be determined as a function of only Val1 or as a function of only Val2 (because their average value is substantially equal to the value of the common mode signal Vcm at time T1target). If T1target is not equal to T2target (e.g., Figure 8C This is also correct.

[0242] exist Fig.8D In the specific example shown, the value of T1target=T2target is chosen to be equal to T_ramp*60%, but of course another value may be used.

[0243] Note that the method with a "control loop" also works for a sensor circuit with only one output signal Vp. In this case, the control loop will be configured to dynamically adjust the threshold value Vt so that the time T1 or count N1 of the first event occurs at a predefined T1target moment. And, it is also possible to derive the digital value Dout of the physical quantity to be measured only from the (dynamically adjusted) value Val1 corresponding to the threshold signal Vt, for example, using a lookup table or a polynomial function with values ​​or coefficients determined during calibration and stored in a non-volatile memory, as described above.

[0244] Preferably, a single predefined waveform of the bias signal is used, but the invention is not limited thereto. If there are multiple predefined waveforms of possible bias signals, a lookup table or a polynomial expression encoding the correspondence between the threshold value Val1 and the quantity to be measured can be determined for each of these bias signals (e.g., by simulation or by calibration), and during actual use of the device, the appropriate table or polynomial needs to be selected (e.g., using an additional parameter indicating which predefined bias signal is used).

[0245] For example, Figure 8C and Fig.8D As illustrated in , embodiments with a tracking loop can measure particularly well physical quantities that may only change slowly.

[0246] Fig. 9 The diagram shows Figure 5 Another variation of the present invention is provided in which the bias signal (e.g., bias voltage) does not increase linearly from zero to a predefined maximum voltage level in each time period, but instead increases linearly from a first voltage level to a second voltage level during even time slots and decreases linearly from the second voltage level to the first voltage level during odd time slots (only partially shown).

[0247] exist Fig. 9 In a variant (not shown), the value of the first voltage level and / or the value of the second voltage level and / or the slope of the bias voltage are not fixed but are dynamically adjusted in each time slot (e.g., depending on measured timer or (one or more) counter events).

[0248] exist Fig. 9 In another or further variation (not shown), two different threshold voltages are used instead of one threshold voltage.

[0249] exist Fig. 9 In another or further variation of the invention, a first event is determined when one of the output voltages crosses a threshold voltage Vt, and a second event is determined when the common mode voltage Vcm crosses a threshold voltage (or a second threshold voltage). As mentioned above (see, e.g. Fig. 6A ), it is not absolutely required that the common mode voltage is actually available, and instead of measuring when the common mode voltage exceeds a certain threshold voltage, the time can also be dynamically calculated, or determined using a lookup table or the like.

[0250] exist Figures 5 to 9 In all the embodiments illustrated in , it is assumed that the periodic measurements are performed during subsequent time slots with a predefined duration (eg T_ramp) and that the physical quantity to be measured does not change significantly during this duration.

[0251] exist Fig.18 In the embodiment, each time slot includes two parts, including a first part, wherein a first digital value Dout1 of a physical quantity (e.g., a magnetic field value or a pressure value) is determined based on one or more time values ​​or count values ​​or thresholds, for example, as discussed above. Figures 5 to 9 and includes a second part, in which a second digital value Dout2 of the physical quantity is determined using a classical ADC circuit. Of course, it is also possible to first determine a digital value using an ADC circuit and then determine another digital value based on timing or counter information.

[0252] Fig.10 A flowchart of a method 1000 for providing a digital value (Dout) indicating a physical quantity to be measured by a sensor circuit or a bridge circuit having two excitation nodes (E1, E2) and at least one readout node (RO1, RO2) (e.g., two readout nodes) is shown, the method comprising the following steps:.

[0253] a) applying (1002) a time-varying bias signal (e.g., Vbias) directly or indirectly to an excitation node (E1, E2) of a sensor circuit or a bridge circuit, so that at least one output node (RO1, RO2) provides at least one time-varying output signal (v1, v2 or Vp, Vn);

[0254] b) determining (1003) at least one time value (T1) or at least one count value (N1) or at least one index value (index1) associated with a first event (event1) at which at least one output signal (Vp) exceeds at least one threshold signal (Vt);

[0255] c) determining (1004) a digital value (Dout) indicative of the physical quantity to be measured based on the at least one time value (T1) or the at least one count value (N1) or the at least one index value (index1).

[0256] The basic principle of the present invention is to convert timing information (or counter information or index information) into digital values. The timing information or counter information or index information is related to the magnitude of the physical quantity to be measured.

[0257] The method may further include the following steps: i) providing a sensor or bridge circuit having two excitation nodes (E1, E2) and at least one output node (RO1, RO2), such as, for example, a Hall element, a horizontal Hall element, a vertical Hall element, or a Wheatstone bridge, or a resistor circuit comprising one or more branches, each branch comprising two or more resistors (e.g., piezoresistors, magnetoresistive resistors, XMR, TMR, AMR, GMR resistors).

[0258] The method may further include providing one or more of the following: a timer, a counter operating at a predefined clock frequency (fCLK), a bias circuit, one comparator or two comparators or more than two comparators, an analog-to-digital converter (ADC), a digital-to-analog converter (DAC), a PWM circuit (pulse width modulation) (optionally followed by a low-pass filter), etc.

[0259] The method may also include the steps of: providing at least one comparator (e.g., one comparator or two comparators); and providing at least one threshold voltage (Vt) to a first input of at least one comparator; and providing at least one read voltage (e.g., v1 or v2) to a second input of at least one comparator. In such embodiments, the first event may be detected, for example, by monitoring when the output level of the comparator changes state. The latter may be implemented, for example, using a polling technique, or may be effectively implemented using an interrupt of a digital processor.

[0260] The method may further include the following steps: providing at least one analog-to-digital converter (ADC); and step a) may further include: using the ADC to repeatedly digitize the at least one output voltage or the differential voltage formed by the two output voltages; and step b) may further include: repeatedly comparing the multiple digital values ​​with at least one threshold value (for example, by a comparison device (for example, by a programmable controller)).

[0261] The method may comprise a further step for converting the digital value Dout into a current value, a torque value, a linear or angular position value, or another physical quantity, for example using a look-up table, or using a mathematical formula, or a combination of these.

[0262] exist Fig.10 In certain embodiments of method 1000, step b) includes: determining only one time value or only one count value (e.g., T1 or T2, or N1 or N2, or index1 or index2); and step c) includes: determining Dout based on the single time value or based on the single count value.

[0263] Fig.11 Shows Fig.10A variation of the method.

[0264] Wherein step b) comprises: determining (1103) a first time value (T1) or a first count value (N1) or a first index value (index1) associated with a first event (event1), at which the first output signal (Vp) exceeds a first threshold signal (Vt, Vt1); and determining a second time value (T2) or a second count value (N2) or a second index value (index2) associated with a second event (event2), at which the second output signal (Vn) exceeds a second threshold signal (Vt, Vt2), and the second threshold signal (Vt, Vt2) is equal to or different from the first threshold signal (for example, Figure 5 or Figure 7 or Fig. 8A );

[0265] And wherein step c) includes: determining (1104) a digital value (Dout) indicating a physical quantity to be measured by the sensor or bridge circuit based on the first time value and the second time value (T1, T2), or based on the first count value and the second count value (N1, N2), or based on the first index value and the second index value (index1, index2), or based on the difference between the first time value and the second time value (ΔT), or based on the difference between the first count value and the second count value (ΔN), or based on the difference between the first index value and the second index value (Δindex).

[0266] Detection of a first event may be performed using a first comparator, wherein a first threshold voltage (Vt1) is applied to a first input of the first comparator and a first output voltage (Vp) is applied to a second input of the first comparator, and detection of a second event may be performed using a second comparator, wherein a second threshold voltage (Vt2) is applied to a first input of the second comparator and a second output voltage (Vp) is applied to a second input of the second comparator.

[0267] Fig.12 Shows Fig.10 Another variation of the method.

[0268] Further comprising step d): generating (1205) a time-varying common mode signal (Vcm), the common mode signal (Vcm) being, for example, R*Vbias or as (Vp+Vn) / 2, where R is a predefined ratio and Vbias is a bias signal (e.g., a bias voltage);

[0269] And wherein step b) comprises: determining (1203) a first time value (T1) or a first count value (N1) or a first index value (index1) associated with a first event (event1), at which the first output signal (v1 or Vp) exceeds a first threshold signal (Vt, Vt1); and determining a second time value (T2) or a second count value (N2) or a second index value (index2) associated with a second event (event2), at which the common mode signal (Vcm) exceeds a second threshold signal (Vt, Vt2), and the second threshold signal (Vt, Vt2) is equal to or different from the first threshold signal;

[0270] And wherein step c) includes: determining (1204) a digital value (Dout) indicating a physical quantity to be measured by the sensor or bridge circuit based on the first time value and the second time value (T1, T2), or based on the first count value and the second count value (N1, N2), or based on the first index value and the second index value (index1, index2), or based on the difference between the first time value and the second time value (ΔT), or based on the difference between the first count value and the second count value (ΔN), or based on the difference between the first index value and the second index value (Δindex).

[0271] Figure 6B An example of this method is illustrated in FIG.

[0272] As already mentioned above, the time value T2 or count value N2 associated with this second event when Vcm crosses the threshold signal is actually known in advance (for a given waveform of the bias signal and a given threshold signal), and it is therefore not really necessary to measure this value, but when it is measured it can be used, for example, for error detection.

[0273] Fig.13 Shows Fig.12 A variation of the method in which the value of the second event (at the second event, the common mode signal Vcm crosses the second threshold) is not actually measured, but instead a reference time value (T_ref) or a reference count value (Nref) is used. The method 1300 has the following steps:

[0274] a) applying (1302) a time-varying bias signal (e.g., Vbias) to an excitation node (E1, E2) so that at least one output node (RO1, RO2) provides at least one time-varying output signal (v1, v2 or Vp, Vn);

[0275] b) determining (1303) a first time value (T1) or a first count value (N1) or a first index value (index1) associated with a first event (event1), at which the first output signal (v1 or Vp) exceeds a first threshold signal (Vt, Vt1); and using a predefined second time value (T2ref) or a predefined second count value (N2ref) or a predefined second index value (index2ref) associated with a second event (event2), at which the common mode signal (Vcm) exceeds a second threshold signal (Vt, Vt2), and the second threshold signal (Vt, Vt2) is equal to or different from the first threshold signal;

[0276] c) determining (1304) a digital value (Dout) indicating a physical quantity to be measured by the sensor or bridge circuit based on the first time value and the second time value (T1, T2ref), or based on the first count value and the second count value (N1, N2ref), or based on the first index value and the second index value (index1, index2ref), or based on the difference (ΔT) between the first time value and the second time value, or based on the difference (ΔN) between the first count value and the second count value, or based on the difference (Δindex) between the first index value and the second index value.

[0277] Fig. 6A The middle figure shows an example of this embodiment, in which the second threshold signal Vt2 is equal to the first threshold signal Vt1.

[0278] Fig.14 A flow chart showing a method 1400 of determining in a reliable manner a digital value indicative of a physical quantity to be measured by a sensor or bridge circuit having two excitation nodes (E1, E2) and at least one output node (e.g., two output nodes (RO1, RO2));

[0279] The method comprises the following steps:

[0280] i) determining a first digital value Dout1 indicative of a physical quantity to be measured based on one or more of the time values ​​or counter values ​​associated with one or more events occurring when a time-varying bias signal (Vbias) is applied to the sensor or bridge circuit during a first time period; e.g. using Figures 10 to 13 Any method in the method.

[0281] ii) determining a second digital value Dout2 indicative of the physical quantity to be measured using an analog-to-digital converter (ADC) circuit (e.g., a classical ADC circuit) while applying a constant bias signal (e.g., a constant bias voltage or a constant bias current) during a second time period;

[0282] iii) determining a validity signal indicating an error.

[0283] Step iii) may include detecting an error during a first time period, for example by detecting that one or more of the following: the first output signal (e.g., Vp), the second output signal (e.g., Vn), the common mode signal (e.g., Vcm, if generated) does not exceed a threshold signal (e.g., Vt). Alternatively or additionally, step iii) may include detecting an inconsistency between the first digital value (Dout1) and the second digital value (Dout2), for example using a predefined criterion, which may depend on, for example, the resolution of the ADC, the accuracy of the timing circuit, etc.

[0284] In an embodiment, the three steps i) to iii) of the method 1400 are performed by a sensor device 1730 including the sensor or bridge circuit 1740. In this case, the sensor device 1730 may output a digital value (e.g., one of the digital values ​​Dout1, Dout2, or an average of the two values, or a weighted average of the two values) as an indication of the physical quantity to be measured, and / or may output a validity signal indicating a detected error.

[0285] In an embodiment, steps i) and ii) are performed by a sensor device 1730 comprising the sensor or bridge circuit 1740, and step iii) is performed by an external processor (not shown) external to the sensor device. In this case, the sensor device outputs two digital values ​​Dout1, Dout2, and the external processor performs a consistency check on these values. The result of this consistency check can then be used as a validity signal.

[0286] Figures 15 to 17 A high-level block diagram of a circuit 1520, 1620, 1720 and an integrated sensor device 1530, 1630, 1730 for determining a digital value "Dout" indicating a physical quantity to be measured by a sensor or a bridge circuit 1540, 1640, 1740 having two excitation nodes E1, E2 and at least one output node RO1, RO2, such as, for example, a Hall element, or a Wheatstone bridge, or a resistor network comprising at least two resistors connected in series, or a value derived from the digital value (e.g., linear or angular position, current value, torque value).

[0287] Fig.15An illustrative example of an integrated sensor device 1530 is shown, which includes at least one such sensor or bridge circuit, and circuit 1520, which is operably connected to the at least one sensor or bridge circuit 1540 and is configured to, for example, perform Figures 10 to 14 The method illustrated in any one of the foregoing determines at least one digital value Dout indicative of the physical quantity to be measured. Circuit 1520 may be referred to as a "sensing and digitizing circuit" and comprises:

[0288] A bias circuit 1521 configured to generate a time-varying bias signal (e.g., Vbias) and apply the time-varying bias signal (e.g., Vbias) to an excitation node E1, E2 of at least one sensor or bridge;

[0289] a threshold generator 1522 configured to generate at least one threshold signal or value (eg, an analog threshold voltage or a digital threshold);

[0290] Comparison means 1523, which is configured to detect at least a first event event1, at which at least one readout signal (e.g., v1 or v2 or Vp or Vn) or a signal or value derived therefrom exceeds at least one threshold signal (e.g., a threshold voltage Vt) or a threshold. As mentioned above, the comparison can be performed in the analog domain or in the digital domain. In the latter case, at least one readout signal from at least one sensor is first digitized by an ADC (not shown).

[0291] A timer (not shown) or counter 1525. The counter may be configured to operate at a predefined clock frequency. The clock signal may be generated internally in the integrated sensor device in a known manner (e.g., using an RC oscillator or crystal oscillator circuit), or may be provided to a clock pin of the integrated sensor device, etc.

[0292] A digital processor 1526, such as a programmable microcontroller or a digital signal processor (DSP). The processor may be configured to perform Figures 10 to 14 Executable instructions for at least step b) and step c) of the method illustrated in any one of . When a predefined (or reference) time value, or a predefined (or reference) count value, or a predefined (or reference) index value is used, the time value or count value can be hard-coded, or stored in a non-volatile memory connected to or incorporated into the digital processor. When a polynomial expression is used, the coefficients of the polynomial can be stored in the non-volatile memory. When a table (also known as a LUT, "lookup table") and an index are used to generate the bias signal, the values ​​of the table can also be stored in the non-volatile memory.

[0293] Although not explicitly shown, the sensor device may also include at least one amplifier (eg, a differential amplifier configured to amplify a differential voltage at output nodes of the sensor or bridge circuit).

[0294] The "comparing means" may include one or more "comparators" (e.g., in the case where the comparison is performed in the analog domain), or the comparison may be performed in software, e.g., as executable instructions executed by the digital processor 1526. As an example, if the detection of event1 and / or event2 is performed in the analog domain, a single comparator per sensor (or per bridge) may be sufficient to perform Fig.10 or Fig.13 However, each sensor (or each bridge) would require two comparators to perform Fig.11 or Fig.12 or Fig.14 If the detection of event1 and / or event2 is performed in the digital domain, no (analog) comparator is necessary, but the comparison will be performed by a digital processor, as graphically indicated by the dashed rectangle surrounding the comparison means and the digital processor.

[0295] In the case where one or more analog comparators are used, the output of each comparator can be connected to (one or more) separate inputs of the processor 1526, and the processor can be configured to generate an interrupt when one of these inputs changes state (e.g., a rising edge and / or a falling edge (depending on the implementation)), and the processor may have an interrupt service routine for determining and further processing (e.g., temporarily storing) a timer value or count value.

[0296] In the case of multiple sensors (or bridge circuits) and in the case of performing the detection of the event(s) in the analog domain using analog comparators, each of the sensors (or bridges) may provide one or two or more output signals to a corresponding comparator or to a corresponding set of two comparators. (For example, in the case of Figure 2B In the case of the sensor structure illustrated in FIG. 1 and / or in the case where a common mode signal Vcm is provided, more than two output signals may be provided).

[0297] The advantage is that a single processor with, for example, four inputs can be used in a single time period (e.g., with Figure 5 The duration T_ramp) illustrated in FIG. 1 can easily determine four different time values ​​or four different count values, which indicate four physical quantities (eg, four magnetic field components) measured by the four Hall elements.

[0298] Fig.15Many variations of the circuit 1520 shown in may be possible. For example:

[0299] The timer or counter may be a hardware component external to the digital processor, or may be incorporated within the digital processor;

[0300] The bias circuit 1521 may be configured to generate a linearly increasing voltage signal Vbias that varies, for example, from a first voltage value to a second voltage value. Suitable circuits for generating a linearly increasing ramp are known in the art and therefore need not be described in detail herein. Suffice it to say that such circuits may include an operational amplifier with a feedback loop. The bias circuit may be controlled (e.g., started, stopped, reset) by a digital processor;

[0301] The bias voltage may start at zero and increase linearly to a value Vmax (e.g., Figure 5 ), but this is not absolutely necessary, and the bias circuit can be configured to start from a non-zero value and increase to a value different from Vmax. A linearly increasing bias voltage is generated during even time slots and a linearly decreasing bias voltage is generated during odd time slots (e.g., as shown in Fig. 9 It is also possible to dynamically change the duration of the ramp (ie, the duration of the time slot), and / or dynamically change the slope of the bias voltage, etc.

[0302] The bias circuit may also be configured to generate a nonlinear signal (eg, an exponential signal or a sinusoidal signal). For example, an exponential signal may be generated by applying a step function to an RC circuit.

[0303] exist Fig.15 In a variation of the present invention, the circuit 1520 further includes a digital-to-analog converter (DAC), and the processor 1526 is configured to generate a time-varying bias signal using the DAC. The bias circuit may further include a filter (e.g., a low-pass filter) for filtering the signal generated by the DAC signal.

[0304] The integrated sensor device 1530 can be implemented on a single semiconductor substrate comprising (among other things) at least one sensor or bridge circuit and a digital processor 1526, but this is not absolutely required, and in another embodiment, at least one sensor or bridge circuit 1540 is implemented on a first semiconductor substrate and the digital processor 1525 is implemented on a second semiconductor substrate, and the first and second semiconductor substrates are interconnected and embedded in a single packaged device.

[0305] Fig.16 A circuit including one or more sensors or bridge circuits 1640 ( Fig.1616), and an illustrative example of an integrated sensor device 1630 of the sensing and digitizing circuit 1620. The sensing and digitizing circuit 1620 and the sensor device 1630 can be viewed as Fig.15 1620 and device 1530, but additionally includes a temperature sensor 1627. The temperature sensor can be configured to measure the temperature of a single semiconductor substrate including at least one sensor 1640 and processor 1626, or can be configured to measure the temperature of a first substrate including at least one sensor or bridge circuit 1640. Processor 1626 can be further configured to, for example, adjust a threshold voltage according to temperature, or Figures 10 to 14 The measured temperature is taken into account when providing the digital value Dout in step c) of the method or when converting the digital value into another physical quantity (eg current, torque, position).

[0306] Fig.16 Circuit 1620 also illustrates that digital processor 1626 may have a clock input and may have an internal timer or an internal counter.

[0307] against Fig.15 The possible variants described also apply here.

[0308] Fig.17 An illustrative example of an integrated sensor device 1730 capable of determining a digital value Dout for a physical quantity to be measured and capable of detecting errors is shown. The integrated sensor device 1730 comprises at least one sensor or bridge circuit 1740 and a circuit 1720 configured to provide a first digital value Dout1 in a manner as described above. However, the sensor device 1730 further comprises an analog-to-digital converter ADC 1731 (e.g., a classical ADC) configured to digitize one or both of the output signals (e.g., output voltages Vp, Vn) and / or to digitize a differential voltage Vdiff formed by two readout nodes RO1, RO2, and to provide a second digital value Dout2.

[0309] In an embodiment, the sensor device 1730 is further configured for detecting an error related to the formation of the first digital value Dout1 , for example by detecting that the first event and / or the second event does not occur without an expected time span.

[0310] In an embodiment, the sensor device 1730 is further configured to perform a consistency test of the first digital value Dout1 and the second digital value Dout2, and to provide at least one of the following: the first digital value and the second digital value or digital values ​​derived therefrom, and an error signal.

[0311] In an embodiment, the sensor device 1730 is further configured to provide the first digital value Dout1 and the second digital value Dout2, for example as output signals to an external controller (not shown), for allowing the external controller to perform a consistency test.

[0312] Such an integrated sensor device 1730 is more suitable for applications requiring functional safety due to its error detection capabilities, for example, for use in automotive or robotic applications.

[0313] Notice, Fig.17 The integrated sensor device shown in has a first processor 1726a and another processor 1726b, the first processor 1726a as part of the sensing and digitizing circuit 1720, and the other processor 1726b can be configured to output two digital values ​​and / or to test the consistency between the two digital values ​​Dout1 and Dout2, but two separate processors are not absolutely necessary, and the functions of the two processors 1726a, 1726b can be combined / implemented in a single processor. A variant of the sensor device 1730 with a single digital processor is contemplated, but not explicitly shown.

[0314] exist Fig.17 In a variation of , ADC circuit 1731 is replaced by a second sensing and digitizing circuit that is identical to circuit 1720 and uses the same bias signal and threshold signal(s).

[0315] exist Fig.17 In another variation, ADC circuit 1731 is replaced by a second sensing and digitization circuit that is similar to circuit 1720 but different from circuit 1720, for example, using a different bias signal and / or (one or more) threshold signals, and / or using a polynomial instead of a lookup table, and / or using a lower clock frequency, and / or using a smaller lookup table (having fewer entries, resulting in lower resolution but occupying less memory space), etc.

[0316] Fig.18 An illustrative example of a sensing and digitizing scheme with two digitizing parts is shown. The timing scheme can be determined by Fig.14 by means of and / or by Fig.17In the example shown, a first digital value Dout1 is determined during a first portion, wherein a time-varying bias signal is applied to at least one sensor or bridge circuit using a timer or counter as described above; and a second digital value Dout2 is determined during a second portion, wherein a constant bias signal is applied to at least one sensor or bridge circuit, and wherein one or both of the output signals (e.g., output voltages Vp, Vn) and / or a differential voltage Vdiff between readout nodes are digitized using an analog-to-digital converter circuit (e.g., a classic ADC).

Claims

1. A method (1000) of providing a digital value (Dout) indicative of a physical quantity to be measured by a sensor circuit (140) or a bridge circuit (240), the sensor circuit (140) or the bridge circuit (240) having two excitation nodes (E1, E2) and at least one output node (RO1, RO2), the method comprising the following steps: a) applying (1002) a time-varying bias signal (Vbias) having a predefined waveform or a configurable waveform to the excitation node (E1, E2), so that the at least one output node (RO1, RO2) provides at least one time-varying output signal (Vp, Vn); b) using at least one threshold signal (Vt) having a predefined or configurable value or a predefined or configurable waveform; c) determining (1003) at least one time value (T1) or at least one count value (N1) or at least one index value (index1) associated with a first event (event1), at which the at least one output signal (Vp) exceeds the at least one threshold signal (Vt); d) determining (1004) said digital value (Dout) indicative of said physical quantity to be measured based on said at least one time value (T1) or count value (N1) or index value (index1).

2. The method (1100; 1200; 1300) according to claim 1, in, Step b) comprises: using a single threshold signal (Vt) having a predefined value or a configurable value or a predefined waveform; Wherein step c) comprises: determining (1003) a single time value (T1) or a single count value (N1) or a single index value (index1) associated with a single event (event1), at which the at least one output signal (Vp) exceeds the single threshold signal (Vt); And wherein step d) comprises: determining (1004) the digital value (Dout) based on the single time value (T1) or the count value (N1) or the index value (index1).

3. The method (1200) of claim 1, in, The sensor circuit (140) or the bridge circuit (240) has two output nodes (RO1, RO2); Wherein, step a) enables the two output nodes (RO1, RO2) to provide a first time-varying output signal (Vp) and a second time-varying output signal (Vn); Wherein, step b) comprises: using a first threshold signal (Vt, Vt1), the first threshold signal having a first predefined value or a first configurable value or a first predefined waveform, and using a second threshold signal (Vt, Vt2), the second threshold signal being equal to or different from the first threshold signal, the second threshold signal having a second predefined value or a second configurable value or a second predefined waveform; And wherein the method further comprises step e): generating (1205) a time-varying common mode signal (Vcm); And wherein step c) comprises: determining (1203) a first time value (T1) or a first count value (N1) or a first index value (index1) associated with a first event (event1), at which the first output signal (v1, Vp) exceeds the first threshold signal (Vt, Vt1); and determining a second time value (T2) or a second count value (N2) or a second index value (index2) associated with a second event (event2), at which the common mode signal (Vcm) exceeds the second threshold signal (Vt, Vt2); And wherein step d) includes: determining (1204) the digital value (Dout) based on the first time value (T1) and the second time value (T2), or based on the first count value (N1) and the second count value (N2), or based on the first index value (index1) and the second index value (index2), or based on the difference (ΔT) between the first time value and the second time value, or based on the difference (ΔN) between the first count value and the second count value, or based on the difference (Δindex) between the first index value and the second index value.

4. The method (1300) of claim 1, in, Step b) comprises: using a first threshold signal (Vt, Vt1), the first threshold signal having a first predefined value or a first configurable value or a first predefined waveform, and using a second threshold signal (Vt, Vt2), the second threshold signal being equal to or different from the first threshold signal, the second threshold signal having a second predefined value or a second configurable value, or a second predefined waveform; Wherein, step c) comprises: determining (1303) a first time value (T1) or a first count value (N1) or a first index value (index1) associated with a first event (event1), at which the first output signal (v1, Vp) exceeds the first threshold signal (Vt, Vt1); and determining a predefined second time value (T2ref) or a predefined second count value (N2ref) or a second index value (index2ref) associated with a second event (event2), at which the common mode signal (Vcm) exceeds the second threshold signal (Vt, Vt2); And wherein step d) includes: determining (1304) the digital value (Dout) based on the first time value (T1) and the second time value (T2ref), or based on the first count value (N1) and the second count value (N2ref), or based on the first index value (index1) and the second index value (index2ref), or based on the difference (ΔT) between the first time value and the second time value, or based on the difference (ΔN) between the first count value and the second count value, or based on the difference (Δindex) between the first index value and the second index value.

5. The method (1000; 1100; 1200; 1300) according to claim 1, in, The at least one threshold signal or threshold value (Vt; Vtp, Vtn) has a predefined voltage level or a predefined value; Or wherein the at least one threshold signal (Vt; Vtp, Vtn) has a configurable voltage level or a configurable value.

6. The method (1100) according to claim 1, in, The sensor circuit (140) or the bridge circuit (240) has two output nodes (RO1, RO2); Wherein, step b) comprises: using a first threshold signal (Vt, Vt1), the first threshold signal having a first predefined value or a first configurable value or a first predefined waveform, and using a second threshold signal (Vt, Vt2), the second threshold signal being equal to or different from the first threshold signal, the second threshold signal having a second predefined value or a second configurable value or a second predefined waveform; Wherein, step a) enables the two output nodes (RO1, RO2) to provide a first time-varying output signal (Vp) and a second time-varying output signal (Vn); Wherein, step c) comprises: determining (1103) a first time value (T1) or a first count value (N1) or a first index value (index1) associated with a first event (event1), at which the first output signal (Vp) exceeds the first threshold signal (Vt, Vt1); and determining a second time value (T2) or a second count value (N2) or a second index value (index2) associated with a second event (event2), at which the second output signal (Vn) exceeds the second threshold signal (Vt, Vt2); And wherein step d) includes: determining (1304) the digital value (Dout) based on the first time value (T1) and the second time value (T2), or based on the first count value (N1) and the second count value (N2), or based on the first index value (index1) and the second index value (index2), or based on the difference (ΔT) between the first time value and the second time value, or based on the difference (ΔN) between the first count value and the second count value, or based on the difference (Δindex) between the first index value and the second index value.

7. The method according to claim 6, in, The method further comprises: determining a first threshold value (Val1) and a second threshold value (Val2), applying these values ​​to at least one digital-to-analog converter to generate the first threshold signal (Vt1) and the second threshold signal (Vt2), and dynamically adjusting these values ​​(Val1, Val2) in a control loop so that the first event substantially coincides with the second event, or so that the difference between the first time value (T1) and the second time value (T2), or so that the difference between the first count value (N1) and the second count value (N2) is substantially equal to a predefined value; And wherein step d) includes: considering the first threshold value (Val1) and the second threshold value (Val2) as a first index value and a second index value, and determining (1104) the digital value (Dout) based on the first index (index1) and the second index (index2), or based on the difference (Δindex) between the first index and the second index.

8. The method (1000; 1100; 1200; 1300) according to claim 1, in, The bias signal of step a) has a waveform having a linearly increasing portion or a linearly decreasing portion; or wherein the bias signal in step a) has a waveform with an exponential portion; Or wherein the bias signal in step a) has a sinusoidal waveform.

9. The method (1000; 1100; 1200; 1300) according to claim 1, Further comprising the steps of: Measuring temperature; And wherein the method further comprises: adjusting at least one threshold voltage (Vt, Vt2) based on the measured temperature; Or wherein the method further includes: based on the measured temperature, adjusting at least one measured time value (T1, T2), or adjusting at least one measured count value (N1, N2), or adjusting at least one measured index value (index1, index2), or adjusting the difference (ΔT) between the first time value and the second time value, or adjusting the difference (ΔN) between the first count value and the second count value, or adjusting the difference (Δindex) between the first index value and the second index value.

10. The method (1000; 1100; 1200; 1300) according to claim 1, in, The sensor circuit (140) is a Hall element, or includes at least one Hall element; or wherein the sensor circuit (140) comprises at least two resistors connected in series; Or wherein the bridge circuit is a Wheatstone bridge, or includes at least one Wheatstone bridge. Or wherein the bridge circuit comprises a plurality of branches, and wherein each branch comprises at least two resistors.

11. A circuit (1520; 1620; 1720) for providing a digital value (Dout) indicative of a physical quantity to be measured by a sensor circuit (140) or a bridge circuit (240), the sensor circuit (140) or the bridge circuit (240) having two excitation nodes (E1, E2) and at least one readout node (RO1, RO2), the circuit comprising: Bias circuit (1521; 1621; 1721)； a threshold generator (1522; 1622; 1722) for generating at least one threshold signal or value; At least one of the following: a timer, a counter, a look-up table with a DAC; Comparison means (1523; 1623; 1723) for comparing the at least one output signal (Vp) or a signal or value derived from the at least one output signal (Vp) with the at least one threshold signal or value; A controller (1526; 1626; 1726a) configured to perform the method according to claim 1.

12. An integrated sensor device (1530; 1630; 1730), the integrated sensor device comprising: At least one sensor circuit (140) or a bridge circuit (240), the at least one sensor circuit (140) or the bridge circuit (240) having two excitation nodes (E1, E2) and at least one readout node (RO1, RO2); At least one circuit (1520; 1620; 1720) according to claim 11 is operably connected to the excitation node (E1, E2) of the at least one sensor circuit (140) or the bridge circuit (240) and to the at least one readout node (RO1, RO2) of the at least one sensor circuit (140) or the bridge circuit (240).

13. The integrated sensor device (1530; 1630; 1730) according to claim 12, Includes a plurality of at least two sensors or bridge circuits.

14. The integrated sensor device (1530; 1630; 1730) according to claim 13, further comprising one or two comparators for each sensor or bridge circuit; in, The output of each comparator is connected to a corresponding input of the controller (1526; 1626; 1726a).

15. The integrated sensor device (1730) according to claim 12, in, The circuit (1520; 1620; 1720) is configured to provide a first digital value (Dout1); and wherein the integrated sensor device (1730) further comprises an analog-to-digital converter (ADC 1731) configured to digitize one or both of the read voltages (Vp, Vn) or to digitize a differential voltage (Vdiff) formed by two read nodes (RO1, RO2) and to provide a second digital value (Dout2); The sensor device (1730) is further configured to provide the first digital value (Doutl) and the second digital value (Dout2) for allowing an external controller to perform a consistency test, or is further configured to perform a consistency test of the first digital value (Doutl) and the second digital value (Dout2), and to provide at least one of the following: the first digital value and the second digital value, or a digital value derived from the first digital value and the second digital value, and an error signal.

Images