Method and system for diagnosing magnetic sensor

Abstract

The invention relates to a method and a system for diagnosing a magnetic sensor. A magnetic sensor circuit includes a plurality of magnetic sensors having bias input and output terminals and first and second measurement terminals. The circuit includes a diagnostic sensor having a bias input and a bias output terminal and first and second measurement terminals. The circuit includes a first multiplexer configured to selectively couple a current source to the bias input terminal of the magnetic sensor or the bias input terminal of the diagnostic sensor; and a second multiplexer configured to selectively couple the bias output terminal of the magnetic sensor or the bias output terminal of the diagnostic sensor to a first terminal of a switch. The circuit includes a third multiplexer configured to selectively couple the measurement terminal of the magnetic sensor or the measurement terminal of the diagnostic sensor to a differential input terminal of an amplifier.

Description

[0001] Information related to divisional application

[0002] This case is a divisional application. The parent application of this divisional application is the invention patent application filed on May 17, 2021, with application number 202180032827.9 and title "Method and System for Diagnosing Magnetic Sensors". Technical Field

[0003] This description generally pertains to magnetic sensors. Background Technology

[0004] For example, a Hall effect sensor's magnetic sensor is a device used to measure the strength of a magnetic field. The magnetic sensor provides an output voltage proportional to the magnetic field strength. Magnetic sensors are used for proximity sensing, position and velocity detection, and current sensing. Hall effect sensors can be combined with threshold detection circuitry to act as switches.

[0005] Due to safety requirements in automotive applications, time-of-flight diagnostics of Hall effect sensors are necessary to verify their integrity. For time-of-flight diagnostics, a known magnetic field is typically created and isolated from external magnetic fields. Current systems incorporate on-chip coils built into integrated circuits to create a localized magnetic field. These systems require additional on-chip area and consume significant power. Furthermore, current systems are often unreliable due to the challenges associated with isolating the localized magnetic field from external magnetic fields. Summary of the Invention

[0006] In one aspect, a magnetic sensor circuit includes a plurality of magnetic sensors having corresponding bias input and bias output terminals and corresponding first and second measurement terminals. The magnetic sensor circuit includes a diagnostic sensor having bias input and bias output terminals and first and second measurement terminals. The magnetic sensor circuit includes a first multiplexer configured to selectively couple a current source to either the bias input terminal of the magnetic sensor or the bias input terminal of the diagnostic sensor. The magnetic sensor circuit includes a second multiplexer configured to selectively couple either the bias output terminal of the magnetic sensor or the bias output terminal of the diagnostic sensor to a first terminal of a switch. The switch includes a second terminal coupled to a ground terminal and includes a gate. The magnetic sensor circuit includes a third multiplexer configured to selectively couple either the measurement terminal of the magnetic sensor or the measurement terminal of the diagnostic sensor to a differential input terminal of an amplifier.

[0007] Additionally, the switch is an NFET, with a first terminal being the drain and a second terminal being the source. The NFET is turned on to electrically connect the bias output terminal to the ground terminal.

[0008] Additionally, the diagnostic sensor includes four resistors connected in a Wheatstone bridge configuration defining the first, second, third, and fourth terminals, wherein two opposite terminals are selected as the bias input and bias output terminals, and the other two terminals are selected as the measurement terminals.

[0009] Additionally, the direction of current flow in the diagnostic sensor is periodically changed by switching adjacent terminals and their opposite terminals as the bias input and bias output terminals, respectively, and switching to two other terminals as the measurement terminals.

[0010] Additionally, during the first phase, the first and third terminals are selected as the bias input and bias output terminals, and the second and fourth terminals are selected as the measurement terminals, wherein during the second phase, the second and fourth terminals are selected as the bias input and bias output terminals, and the first and third terminals are selected as the measurement terminals.

[0011] Additionally, the magnetic sensor circuit includes a demodulator having differential input terminals coupled to the differential output terminal of the amplifier and an output terminal. The magnetic sensor circuit also includes an analog-to-digital converter having input terminals coupled to the output terminal of the demodulator and an output terminal. Furthermore, the magnetic sensor circuit includes an operational amplifier having first and second input terminals coupled to the differential output terminal of the third multiplexer, a third input terminal coupled to the common-mode terminal, and an output terminal coupled to the gate of the switch.

[0012] Additionally, the diagnostic sensor generates a non-sinusoidal reference voltage at the differential output terminal, wherein the amplitude of the reference voltage alternates between a minimum and a maximum value. The reference voltage includes a diagnostic sensor output voltage component responsive to a magnetic field and a diagnostic sensor offset voltage component resulting from a mismatch in the diagnostic sensor.

[0013] Additionally, a self-diagnostic magnetic sensor circuit includes a plurality of magnetic sensors having corresponding bias input and bias output terminals, as well as corresponding first and second measurement terminals. The magnetic sensor circuit includes a diagnostic sensor having bias input and bias output terminals, as well as first and second measurement terminals. The magnetic sensor circuit includes a first multiplexer configured to couple a current source to the bias input terminal of the magnetic sensor during an operation phase, and to couple the current source to the bias input terminal of the diagnostic circuit during a diagnostic phase. The magnetic sensor circuit includes a second multiplexer configured to couple the bias output terminal of the magnetic sensor to a first terminal of a switch during the operation phase and to couple the bias output terminal of the diagnostic sensor to the first terminal of the switch during the diagnostic phase, and includes a third multiplexer configured to couple the measurement terminal of the magnetic sensor to a differential input terminal of an amplifier during the operation phase and to couple the measurement terminal of the diagnostic sensor to the differential input terminal of the amplifier during the diagnostic phase.

[0014] In an additional aspect, a method for diagnosing a signal chain in a magnetic sensor circuit includes generating a reference voltage by periodically switching the direction of current flow in the diagnostic sensor. The reference voltage is a non-sinusoidal differential voltage whose amplitude alternates between a minimum and a maximum value, wherein the reference voltage includes a diagnostic sensor output voltage component responsive to an external magnetic field and a diagnostic sensor offset voltage component resulting from a mismatch in the diagnostic sensor. The method includes amplifying the reference voltage, wherein the amplified reference voltage is a differential voltage having an amplifier offset voltage component. The method includes demodulating the amplified voltage by filtering the diagnostic sensor offset voltage component and the amplifier offset voltage component, and digitizing the demodulated voltage. The method includes comparing the digitized voltage with the reference voltage to diagnose the signal chain.

[0015] In an additional aspect, the method includes generating the reference voltage by periodically switching the direction of current flow in the diagnostic sensor by respectively switching adjacent terminals and their opposite terminals as the bias input and bias output terminals, and switching to two other terminals as the measurement terminals.

[0016] Additionally, a method for diagnosing a magnetic sensor includes generating a reference voltage by periodically switching the direction of current flow in the magnetic sensor, wherein the reference voltage is a non-sinusoidal differential voltage whose amplitude alternates between a minimum and a maximum value. The reference voltage includes a sensor output voltage component responsive to a magnetic field and a sensor offset voltage component resulting from a mismatch in the magnetic sensor. The method includes amplifying the reference voltage, wherein the amplified reference voltage is a differential voltage including an amplifier offset voltage component. The method includes demodulating the amplified reference voltage by filtering the sensor offset voltage component and the amplifier offset voltage component, and digitizing the demodulated voltage. The method includes using the digitized voltage to determine the sensitivity of the magnetic sensor. Attached Figure Description

[0017] Figure 1 This is a block diagram of a magnetic sensor circuit in an example embodiment.

[0018] Figure 2 Explain the timing diagram.

[0019] Figure 3 This is a schematic diagram of a magnetic sensor in an example embodiment.

[0020] Figure 4 This is a block diagram of the test circuit in an example embodiment.

[0021] Figure 5 This is a flowchart of an example implementation. Detailed Implementation

[0022] Figure 1 This is a block diagram of a magnetic sensor circuit 100 according to an example embodiment. The magnetic sensor circuit 100 operates in two modes: a diagnostic mode and a normal mode. In the diagnostic mode, the magnetic sensor circuit 100 performs self-diagnostics to verify the integrity of the signal chain of the circuit 100. In the normal mode, the magnetic sensor circuit 100 measures the external magnetic field and provides an output voltage representing the external magnetic field.

[0023] The magnetic sensor circuit 100 operates in a working cycle with sleep and active states. For example... Figure 2 The timing diagram illustrates that in sleep state 204, the magnetic sensor circuit 100 is inactive, and in active state 208, the magnetic sensor circuit 100 performs signal chain diagnostic checks 210 and sensor diagnostic checks 214. Afterward, the magnetic sensor circuit 100 performs normal operation 218, also known as Hall effect sensor operation.

[0024] The magnetic sensor circuit 100 includes three magnetic sensors 104A, 104B, and 104C, which are oriented to measure an external magnetic field in the x, y, and z directions, respectively. The magnetic sensor circuit 100 can be constructed using any suitable number of magnetic sensors. The magnetic sensors 104A, 104B, and 104C can be, for example, Hall effect sensors that provide an output voltage representing the strength of the external magnetic field.

[0025] The magnetic sensor circuit 100 includes a diagnostic sensor 108 that provides an output voltage unaffected by an external magnetic field. In an exemplary embodiment, the diagnostic sensor is constructed using resistors (e.g., polysilicon resistors) that do not generate voltage in response to an external magnetic field. The resistors in the diagnostic sensor may be connected in a Wheatstone bridge network. The diagnostic sensor 108 is used to perform self-diagnostics to check the integrity of the signal chain of circuit 100. The diagnostic sensor 108 may, for example, be a resistor network that is insensitive to external magnetic fields.

[0026] Magnetic sensors 104A, 104B, and 104C include corresponding bias input terminals 110A, 110B, and 110C configured to receive bias current. During normal operation, switch S1 couples the bias input terminals 110A, 110B, and 110C to a current source I that provides the bias current. bias Switch S1 can be implemented using a multiplexer.

[0027] Magnetic sensors 104A, 104B, and 104C include corresponding bias output terminals 112A, 112B, and 112C. During normal operation, switch S2 couples the bias output terminals 112A, 112B, and 112C to the first terminal 116 of switch M1. For example, switch S2 may be a multiplexer. Switch M1 has a second terminal 118 coupled to a ground terminal. The ground terminal may be coupled to a ground voltage. Switch M1 may be, for example, an n-channel field-effect transistor (NFET), with its first terminal 116 being the drain and its second terminal 118 being the source. Switch M1 also has a gate. When M1 is turned on, a conduction path is provided for bias current from current source I. bias The current flows to ground.

[0028] Magnetic sensor 104A includes measuring terminals 122A and 122B, magnetic sensor 104B includes measuring terminals 124A and 124B, and magnetic sensor 104C includes measuring terminals 126A and 126B. In response to an external magnetic field, magnetic sensors 104A, 104B, and 104C provide output voltages at the measuring terminals. The output voltages at the measuring terminals represent the strength of the external magnetic field. A switch S3 (e.g., a multiplexer) selectively couples the measuring terminals to differential output terminals 128 and 130. During normal operation, the output voltages generated by magnetic sensors 104A, 104B, and 104C are available at differential output terminals 128 and 130.

[0029] The diagnostic sensor 108 includes a bias input terminal 134 and a bias output terminal 136. The diagnostic sensor 108 also includes measurement terminals 138 and 140. During diagnostic mode, switch S1 couples the bias input terminal 134 to current source I. bias Furthermore, switch S2 couples the bias output terminal 136 to the first terminal 116 of transistor M1, thus in the current source I bias A conductive path is provided between the sensor and ground. Furthermore, during diagnostic mode, switch S3 couples measurement terminals 138 and 140 to differential output terminals 128 and 130. Diagnostic sensor 108 provides an output voltage at measurement terminals 138 and 140 that is unaffected by external magnetic fields.

[0030] The magnetic sensor circuit 100 includes an analog front end (AFE) 150, which may be an amplifier. The AFE 150 includes differential inputs 152 and 154, respectively coupled to differential outputs 128 and 130. During diagnostic mode, switch S4 directs current source I... diagsrc Connect to input 152 of AFE 150, and switch S5 will turn current sink I diagsnk Input 154 is connected to AFE 150. AFE 150 applies a predetermined gain to the differential voltages provided by magnetic sensors 104A to 104C or diagnostic sensor 108 and provides amplified differential signals at outputs 156 and 158. Magnetic sensor circuit 100 includes demodulator 160, which is coupled to receive the amplified differential signals at inputs 162 and 164. Demodulator 160 demodulates the amplified signals and provides a filtered signal at output 166. Analog-to-digital converter (ADC) 168 digitizes the filtered signal.

[0031] In an exemplary embodiment, the magnetic sensor circuit 100 includes an operational amplifier 170 having first and second input terminals 172 and 174 respectively coupled to corresponding differential output terminals 128 and 130 of a third switch S3, and a third input terminal 176 coupled to a common-mode terminal to which a common-mode voltage can be applied. The operational amplifier 170 also includes an output terminal 178 coupled to the gate of switch M1. In response to the differential and common-mode voltages at terminals 128 and 130, the operational amplifier 170 applies a gate voltage to switch M1 to control the current flowing through M1, and thus control the current in magnetic sensors 104A to 104C and diagnostic sensor 108.

[0032] In an example embodiment, the magnetic sensors 104A to 104C and the diagnostic sensor 108 are implemented using four resistors connected in a Wheatstone bridge configuration. Figure 3 The sensor 300 is described, and it may be one of magnetic sensors 104A to 104C or diagnostic sensor 108. The sensor 300 includes four resistors R1, R2, R3, and R4 connected in a bridge configuration, respectively defining first, second, third, and fourth terminals T1, T2, T3, and T4. The sensor 300 operates in four phases, and in each phase, different pairs of opposite terminals are selected as bias input and bias output terminals, while another pair of opposite terminals is selected as measurement terminals. For example, in phase 1, terminals T1 and T3 may be selected as bias input and output terminals, respectively, while the two opposite terminals T2 and T4 may be selected as measurement terminals. During phase 1, switch S1 directs current source I... bias The bias current flows through resistors R1, R2, R3, and R4 and exits through terminal T3. In response to an external magnetic field H1, sensor 300 provides output voltages at measuring terminals T2 and T4. During phase 1, switch S3 couples measuring terminals T2 and T4 to differential output terminals 128 and 130.

[0033] In phase 2, terminals T2 and T4 can be selected as bias input and output terminals, respectively, while the two opposite terminals T1 and T3 can be selected as measurement terminals. During phase 2, switch S1 will switch current source I... bias The bias current flows through resistors R1, R2, R3, and R4 and exits through terminal T4. In response to an external magnetic field H1, sensor 300 provides an output voltage at measuring terminals T1 and T3. During phase 2, switch S3 couples measuring terminals T1 and T3 to differential output terminals 128 and 130.

[0034] In phase 3, terminals T3 and T1 can be selected as bias input and output terminals, respectively, while the two opposite terminals T2 and T4 can be selected as measurement terminals. During phase 3, switch S1 will switch current source I... bias The bias current flows through resistors R1, R2, R3, and R4 and exits through terminal T1. In response to an external magnetic field H1, sensor 300 provides an output voltage at measuring terminals T2 and T4. During phase 2, switch S3 couples measuring terminals T2 and T4 to differential output terminals 128 and 130.

[0035] In phase 4, terminals T4 and T2 can be selected as bias input and output terminals, respectively, while the two opposite terminals T1 and T3 can be selected as measurement terminals. During phase 4, switch S1 will switch current source I... bias The bias current flows through resistors R1, R2, R3, and R4 and exits via terminal T2. In response to an external magnetic field H1, sensor 300 provides an output voltage at measuring terminals T1 and T3. During phase 2, switch S3 couples measuring terminals T1 and T3 to differential output terminals 128 and 130.

[0036] By switching the current source I during each stage bias Coupled to different bias input terminals, the direction of current flow in sensor 300 is periodically changed. Therefore, a periodic non-sinusoidal voltage is generated at the measurement terminal of sensor 300. The amplitude of the non-sinusoidal voltage at the measurement terminal alternates between a minimum and a maximum value.

[0037] During diagnostic mode, the magnetic sensor circuit 100 is configured to check the integrity of magnetic sensors 104A to 104C by measuring the magnetic sensor offset and the offset of AFE 150. In this mode, current source I... bias A predetermined current is supplied to the magnetic sensor. The direction of current flow in the magnetic sensors 104A to 104C is periodically switched. In response to an external magnetic field, the magnetic sensor provides a periodic non-sinusoidal voltage, referred to as the Hall voltage, at the differential output terminals 128 and 130. The output voltage includes the voltage corresponding to the current source I. bias The magnetic sensor's resistance and the external magnetic field's diagnostic sensor offset voltage component, as well as the magnetic sensor's output voltage component, are considered. The offset component is generated due to resistor mismatch in the sensor, while the magnetic voltage component is generated by the magnetic sensor in response to the external magnetic field. Since the external magnetic field can be unknown during diagnostic mode, its effect must be ignored. The signals at differential output terminals 128 and 130 are amplified by AFE 150. At the output of AFE 150, the offset component is added due to mismatch in AFE 150. The signal at the output of AFE 150 can be expressed as:

[0038] V ph(i) = (-1) i+1 V Hall + V OS,Hall,ph(i) + V OS,AFE ,in:

[0039] V ph(i) =AFE output signal for each stage (1, 2, 3, and 4)

[0040] V Hall =Hall effect voltage component

[0041] V OS,Hall,ph(i) =Hall sensor offset voltage component

[0042] V OS,AFE = AFE offset voltage component

[0043] Based on the above:

[0044] V ph(1) + V ph(2) + V ph(3) + V ph(4) = 4(V OS,Hall,ph(i) + V OS,AFE )

[0045] As shown below, even in the presence of an unknown external magnetic field, the integrity of the magnetic sensor can be determined from the sum of the offsets of the magnetic sensor and the analog front end.

[0046] (V OS,Hall,ph(i) + V OS,AFE ) = (1 / 4)(V ph(1) + V ph(2) + V ph(3) + V ph(4) )

[0047] In normal operation, demodulator 160 is used to demodulate the sensor output corresponding to the external field, as follows:

[0048] V ph(1) - V ph(2) + V ph(3) - V ph(4) = 4(V Hall )

[0049] During diagnostic mode, circuit 100 is configured to verify signal chain integrity using diagnostic sensor 108. In an example embodiment, in diagnostic mode, in addition to the bias current I... bias In addition, diagnostic current source I diagsrc and slot I diagsnk It is applied to the diagnostic sensor 108. Diagnostic current source I diagsrc It can be connected to differential terminals 128 and 130 via switch S4, and diagnostic current slot I diagsnk Switch S5 can be connected to differential terminals 128 and 130. Switch S3 connects differential terminals 128 and 130 to diagnostic sensor 108, and thus connects diagnostic current source I. diagsrc and diagnostic current tank I diagsnk Applied to diagnostic sensor 108. Diagnostic current source I diagsrc and diagnostic current tank I diagsnk It has a predetermined value and can be referred to as the reference current of the diagnostic sensor 108.

[0050] I is periodically switched in the diagnostic sensor 108. bias I diagsrc and I diagsnk The direction of current flow. In stages 1 and 3, terminal 180 of the diagnostic current source is switched to terminal 152, and terminal 182 of the diagnostic current tank is switched to terminal 154. In stages 2 and 4, terminal 180 of the diagnostic current source is switched to terminal 154, and terminal 182 of the diagnostic current tank is switched to terminal 152. Unaffected by external magnetic fields and I... bias Under these conditions, the diagnostic sensor 108 provides a periodic non-sinusoidal voltage, referred to as the diagnostic reference voltage at the differential output terminals 128 and 130. Two diagnostic currents (I...) diagsrc I diagsnk ) can have the same value (I) diagsrc The diagnostic reference voltage includes the corresponding diagnostic current source (I). diagsrc and the resistance R of the diagnostic sensor diagsns The diagnostic sensor offset component and the known diagnostic reference voltage component are described. The diagnostic sensor offset component is generated due to the mismatch of the resistor in the diagnostic sensor 108, and the known diagnostic reference voltage component is generated by the diagnostic sensor 108, which is unaffected by external magnetic fields, and is attributed to the voltage drop created by the reference diagnostic current flowing through the diagnostic sensor. Since the diagnostic reference current has a known value, the resulting diagnostic reference voltage component also has a known value. The signals at the differential output terminals 128 and 130 are amplified by AFE 150. At the output of AFE 150, an offset component is added to the signal due to the mismatch in AFE 150. The signal at the output of AFE 150 can be expressed as:

[0051] Vph(i) = (-1) i+1 V ref,diag + V OS,Hall,ph(i) + V OS,AFE ,in:

[0052] V ph(i) = AFE output signal for each stage (1, 2, 3, and 4)

[0053] V ref,diag = I diagsrc *R diagsns (Diagnostic reference voltage component)

[0054] V OS,diag,ph(i) =Diagnostic sensor offset voltage component

[0055] V OS,AFE = AFE offset voltage component

[0056] Based on the above:

[0057] V ph(1) - V ph(2) + V ph(3) - V ph(4) = 4(V ref,diag )

[0058] Therefore, signal chain integrity can be determined by obtaining a known output reference voltage based on demodulation at four different stages:

[0059] (V ref,diag ) = (1 / 4)(V ph(1) - V ph(2) +V ph(3) - V ph(4) ).

[0060] In an example embodiment, the magnetic sensor circuit 100 is configured to perform a sensor integrity check to verify the sensitivity of the magnetic sensors 104A to 104C. Figure 4 This describes a simplified circuit 400 for sensor integrity checking of magnetic sensor 104A. The bias input terminal 110A of magnetic sensor 104A is coupled to a current source, and the bias output terminal 112A is coupled to the drain 116 of transistor M1. During sensor integrity checking, the current source uses a known voltage V. diag and resistor R diag Generate current I diag In response to I with a known value diag The magnetic sensor 104A provides a differential output voltage V(d1-d2), which can be expressed as:

[0061] V(d1-d2) = (I diag )*(R Hall )

[0062] Where R Hall It is the equivalent resistance of the magnetic sensor 104.

[0063] In use (V) bg / R diag Replace I diag back:

[0064] V(d1-d2) = (V bg / R diag )*R Hall = K*V bg

[0065] Where K=R Hall / R diag It is defined as a sensitivity constant.

[0066] Therefore, the sensitivity of the magnetic sensor 104A can be determined by measuring the differential voltage V(d1-d2) in response to a known current value. As discussed earlier, the differential voltage can be determined from the output of the ADC 168 converter, which provides a digital signal representing the differential voltage.

[0067] Figure 5 This is a flowchart of a method for diagnosing the signal chain of a magnetic sensor circuit in an example embodiment. In block 504, a reference voltage is generated by periodically switching the direction of current flow in the diagnostic sensor. The reference voltage is a non-sinusoidal differential voltage whose amplitude alternates between a minimum and a maximum value. The reference voltage includes a diagnostic sensor output voltage component in response to a magnetic field and a diagnostic sensor offset voltage component caused by mismatch in the diagnostic sensor. In block 508, the reference voltage is amplified by an analog front end. The amplified voltage is a differential voltage containing an amplifier offset voltage component. In block 512, the amplified reference voltage is demodulated by filtering the diagnostic sensor offset voltage component and the amplifier offset voltage component. In block 516, the demodulated signal is digitized. The digitized signal is used and compared with the reference voltage to diagnose the signal chain.

[0068] Various illustrative components, blocks, modules, circuits, and steps have been described above in their general functional terms. Whether this functionality is implemented as hardware or software depends on the specific application and design constraints imposed on the overall system. The described functionality may be implemented differently for each specific application, but such implementation decisions should not be construed as causing a departure from the scope of this disclosure.

[0069] For the sake of simplicity and clarity, the complete structure and operation of all systems suitable for use with this disclosure are not depicted or described herein. Instead, only the aspects of systems unique to or necessary for understanding this disclosure are depicted and described.

Claims

1. A circuit comprising: A magnetic sensor having a first sensor terminal, a second sensor terminal, a third sensor terminal, and a fourth sensor terminal; A diagnostic sensor having a first diagnostic terminal, a second diagnostic terminal, a third diagnostic terminal, and a fourth diagnostic terminal; A first multiplexer is coupled to the first sensor terminal and the first diagnostic terminal; A second multiplexer is coupled to the second sensor terminal and the second diagnostic terminal; as well as A third multiplexer is coupled to the third sensor terminal, the fourth sensor terminal, the first diagnostic terminal, the second diagnostic terminal, the third diagnostic terminal, and the fourth diagnostic terminal, and the third multiplexer has a first differential output terminal and a second differential output terminal.

2. The circuit according to claim 1, wherein the magnetic sensor is a first magnetic sensor, and the circuit further comprises: The second magnetic sensor has a fifth sensor terminal, a sixth sensor terminal, a seventh sensor terminal and an eighth sensor terminal, wherein the fifth sensor terminal is coupled to the second multiplexer, the sixth sensor terminal is coupled to the second multiplexer, the seventh sensor terminal is coupled to the third multiplexer and the eighth sensor terminal is coupled to the third multiplexer. as well as The third magnetic sensor has a ninth sensor terminal, a tenth sensor terminal, an eleventh sensor terminal and a twelfth sensor terminal, wherein the ninth sensor terminal is coupled to the first multiplexer, the tenth sensor terminal is coupled to the second multiplexer, the eleventh sensor terminal is coupled to the third multiplexer and the twelfth sensor terminal is coupled to the third multiplexer.

3. The circuit of claim 1, wherein the third multiplexer is configured to couple the third diagnostic terminal to the first differential output terminal and the fourth diagnostic terminal to the second differential output terminal.

4. The circuit according to claim 1, wherein the diagnostic sensor comprises: A first resistor having a first resistor terminal and a second resistor terminal; The second resistor has a third resistor terminal and a fourth resistor terminal, the third resistor terminal being coupled to the first resistor terminal, and the first resistor terminal and the third resistor terminal being coupled to the first multiplexer and the third multiplexer. A third resistor has a fifth resistor terminal and a sixth resistor terminal, the fifth resistor terminal being coupled to the third resistor terminal, and the third resistor terminal and the fifth resistor terminal being coupled to the third multiplexer; as well as A fourth resistor has a seventh resistor terminal and an eighth resistor terminal, the seventh resistor terminal being coupled to a second resistor terminal, the second resistor terminal and the seventh resistor terminal being coupled to a third multiplexer, the eighth resistor terminal being coupled to a sixth resistor terminal, and the sixth resistor terminal and the eighth resistor terminal being coupled to the second multiplexer and the third multiplexer.

5. The circuit according to claim 1, wherein: During the first phase, the first diagnostic terminal is a bias input terminal, the second diagnostic terminal is a bias output terminal, the third diagnostic terminal is a first measurement terminal, and the fourth diagnostic terminal is a second measurement terminal; During the second phase, the fourth diagnostic terminal is the bias input terminal, the third diagnostic terminal is the bias output terminal, the first diagnostic terminal is the first measurement terminal, and the second diagnostic terminal is the second measurement terminal; During the third phase, the second diagnostic terminal is the bias input terminal, the first diagnostic terminal is the bias output terminal, the third diagnostic terminal is the first measurement terminal, and the fourth diagnostic terminal is the second measurement terminal; as well as During the fourth phase, the third diagnostic terminal is the bias input terminal, the fourth diagnostic terminal is the bias output terminal, the second diagnostic terminal is the first measurement terminal, and the first diagnostic terminal is the second measurement terminal.

6. The circuit according to claim 1, further comprising: A first switch is coupled to the first differential output terminal and the second differential output terminal; A first current source, which is coupled to the first switch; The second switch is coupled to the third multiplexer; as well as A second current source is coupled to the second switch.

7. The circuit according to claim 6, further comprising: An analog front-end (AFE) has a first AFE input, a second AFE input, a first AFE output, and a second AFE output, wherein the first AFE input is coupled to the first differential output terminal, and the second AFE input is coupled to the second differential output terminal. as well as A demodulator having a first demodulator input, a second demodulator input, a first demodulator output, and a second demodulator output, wherein the first demodulator input is coupled to the first AFE output and the second demodulator input is coupled to the second AFE output.

8. The circuit of claim 7, wherein the first switch is configured to: Couple the first current source to the first AFE input; and The second switch is coupled to the second AFE input.

9. The circuit of claim 6, further comprising a current source coupled to the first multiplexer.

10. The circuit according to claim 9, further comprising: An operational amplifier having a first amplifier input, a second amplifier input, a third amplifier input, and an amplifier output, wherein the first amplifier input is coupled to a first differential output terminal, and the second amplifier input is coupled to a second differential output terminal; as well as A transistor having a first current terminal, a second current terminal, and a control terminal, the control terminal being coupled to the amplifier output, and the first current terminal being coupled to the second multiplexer.

11. The circuit of claim 10, wherein the first multiplexer is configured to couple the first diagnostic terminal to the current source, and the second multiplexer is configured to couple the second diagnostic terminal to the first current terminal.

12. A vehicle comprising: A magnetic sensor circuit includes: A magnetic sensor having a first sensor terminal, a second sensor terminal, a third sensor terminal, and a fourth sensor terminal; A diagnostic sensor having a first diagnostic terminal, a second diagnostic terminal, a third diagnostic terminal, and a fourth diagnostic terminal; A first multiplexer is coupled to the first sensor terminal and the first diagnostic terminal; A second multiplexer is coupled to the second sensor terminal and the second diagnostic terminal; A third multiplexer is coupled to the third sensor terminal, the fourth sensor terminal, the first diagnostic terminal, the second diagnostic terminal, the third diagnostic terminal, and the fourth diagnostic terminal, and the third multiplexer has a first differential output terminal and a second differential output terminal; An analog front-end AFE is coupled to the third multiplexer; Demodulator, which is coupled to the AFE; and An analog-to-digital converter (ADC) coupled to the demodulator.

13. The vehicle of claim 12, wherein the magnetic sensor is a first magnetic sensor, and the magnetic sensor circuit further comprises: A second magnetic sensor has a fifth sensor terminal, a sixth sensor terminal, a seventh sensor terminal and an eighth sensor terminal, wherein the fifth sensor terminal is coupled to the second multiplexer, the sixth sensor terminal is coupled to the second multiplexer, the seventh sensor terminal is coupled to the third multiplexer and the eighth sensor terminal is coupled to the third multiplexer. as well as A third magnetic sensor has a ninth sensor terminal, a tenth sensor terminal, an eleventh sensor terminal, and a twelfth sensor terminal. The ninth sensor terminal is coupled to the first multiplexer, the tenth sensor terminal is coupled to the second multiplexer, the eleventh sensor terminal is coupled to the third multiplexer, and the twelfth sensor terminal is coupled to the third multiplexer.

14. The vehicle according to claim 12, further comprising: A first switch is coupled to the first differential output terminal and the second differential output terminal; A first current source, which is coupled to the first switch; The second switch is coupled to the third multiplexer; as well as A second current source is coupled to the second switch.

15. The vehicle according to claim 14, further comprising: An operational amplifier having a first amplifier input, a second amplifier input, a third amplifier input, and an amplifier output, wherein the first amplifier input is coupled to a first differential output terminal, and the second amplifier input is coupled to a second differential output terminal; as well as A transistor having a first current terminal, a second current terminal, and a control terminal, the control terminal being coupled to the amplifier output, and the first current terminal being coupled to the second multiplexer.

16. The vehicle of claim 15, further comprising a current source coupled to the first multiplexer, wherein the first multiplexer is configured to couple the first diagnostic terminal to the current source, and the second multiplexer is configured to couple the second diagnostic terminal to the first current terminal.

17. A method for diagnosing the signal chain of a magnetic sensor circuit, comprising: A reference voltage is generated by periodically switching the direction of current flow in a diagnostic sensor, wherein the reference voltage is a non-sinusoidal differential voltage, the amplitude of which alternates between a minimum and a maximum value, and wherein the reference voltage includes a diagnostic sensor output voltage component in response to an external magnetic field and a diagnostic sensor offset voltage component caused by mismatch of the diagnostic sensor. The reference voltage is amplified, wherein the amplified reference voltage is a differential voltage having an amplifier offset voltage component; as well as The amplified reference voltage is demodulated by filtering the offset voltage component of the diagnostic sensor and the offset voltage component of the amplifier, and the demodulated voltage is then digitized.

18. The method of claim 17, further comprising comparing the digitized voltage with the reference voltage to diagnose the signal chain.

19. The method of claim 17, further comprising generating the reference voltage by periodically switching the direction of current flow in the diagnostic sensor by switching to adjacent terminals and their opposite terminals, which are respectively bias input terminals and bias output terminals, and switching to two other terminals, which are measurement terminals.

20. The method of claim 17, wherein the transition between the minimum value and the maximum value is instantaneous.

21. A method for diagnosing a magnetic sensor, comprising: A reference voltage is generated by periodically switching the direction of current flow in the diagnostic sensor, wherein the reference voltage is a non-sinusoidal differential voltage, the amplitude of which alternates between a minimum and a maximum value, and wherein the reference voltage includes a sensor output voltage component responsive to a magnetic field and a sensor offset voltage component caused by mismatch of the magnetic sensor. The reference voltage is amplified, wherein the amplified reference voltage is a differential voltage that includes an amplifier offset voltage component; as well as The amplified reference voltage is demodulated by filtering the sensor offset voltage component and the amplifier offset voltage component, and the demodulated voltage is then digitized.

Images