Temperature sensor and circuit

Abstract

A temperature sensor (300) comprising at least one temperature sensing circuit (100). Each temperature sensing circuit (100) comprises a series connection of a first connection node (111), a first capacitor (110), a biasing transistor (140), a second capacitor (150), a second connection node (151), the first capacitor (110) connected to a first reset transistor (120) for biasing the first capacitor to a first bias voltage, the biasing transistor (140) for distributing charge between the first capacitor and the second capacitor after biasing the first capacitor and the second capacitor, the second capacitor (150) connected to a second reset transistor (160) for biasing the second capacitor to a second bias voltage. Each temperature sensing circuit comprises at least one voltage readout node between the first capacitor (110) and the second capacitor (150).

Description

Technical Field

[0001] This invention relates to the field of temperature sensors. More specifically, it relates to temperature sensor circuits that can be integrated onto integrated circuits. Background Technology

[0002] In many applications, integrated circuits (ICs) require embedded temperature sensors, such as for calibrating sensor signals.

[0003] Existing integrated temperature sensor circuits may include, for example, a resistor bridge, wherein the resistors are made of different materials.

[0004] The linearity of this type of resistance temperature sensor may deteriorate at temperatures, for example, below 0°C. Given the varying temperature sensitivity at different temperatures, this sensor typically requires calibration at at least three different temperatures.

[0005] Operating a resistance temperature sensor requires applying current through the resistor. This results in significant power consumption, which should ideally be reduced.

[0006] There is a need for an integrated temperature sensor with improvements to at least one of its characteristics. Compared to existing technologies, the improved temperature sensor may, for example, have improved accuracy, and / or improved linearity and / or lower power consumption. Summary of the Invention

[0007] The purpose of this invention is to provide a good temperature sensor that can be integrated onto an integrated circuit.

[0008] The above objectives are achieved by the method and apparatus according to the present invention.

[0009] In a first aspect, embodiments of the present invention relate to a temperature sensor. The temperature sensor includes at least one temperature sensing circuit. Each temperature sensing circuit includes a first connection node, a first capacitor, a bias transistor, a second capacitor, and a second connection node connected in series. The first capacitor is connected to a first reset transistor for biasing the first capacitor to a first bias voltage. The bias transistor is used to distribute charge between the first and second capacitors after biasing the first and second capacitors. The second capacitor is connected to a second reset transistor for biasing the second capacitor to a second bias voltage.

[0010] Each temperature sensing circuit includes at least one voltage readout node between a first capacitor and a second capacitor.

[0011] An advantage of embodiments of the present invention is that a voltage at at least one readout node can be obtained, which is linearly correlated with temperature.

[0012] In an embodiment of the present invention, the temperature sensor includes two temperature sensing circuits, wherein the ratio of the capacitance of the first capacitor to the capacitance of the second capacitor is different for the two sensing circuits.

[0013] In an embodiment of the present invention, the bias transistor of one temperature sensing circuit in the temperature sensing circuit is an n-channel metal-oxide-semiconductor transistor, and the bias transistor of the other temperature sensing circuit in the temperature sensing circuit is a p-channel metal-oxide-semiconductor transistor.

[0014] In an embodiment of the present invention, the temperature sensor includes a voltage reference circuit for obtaining a predefined bias voltage for biasing the bias transistor.

[0015] In an embodiment of the present invention, the temperature sensor includes a voltage divider for dividing the voltage at the first connection node to obtain a predefined bias voltage for biasing the bias transistor.

[0016] In embodiments of the invention, each temperature sensing circuit includes an injection switch between a first capacitor and a bias transistor, or between a bias transistor and a second capacitor. The injection switch can be turned on for distributing charge, or turned off when the first or second capacitor is biased.

[0017] In an embodiment of the present invention, the first reset transistor of each temperature sensing circuit is a p-channel metal-oxide-semiconductor transistor.

[0018] In an embodiment of the present invention, the first reset transistor is connected in parallel with the first capacitor.

[0019] In an embodiment of the present invention, the second reset transistor of each temperature sensing circuit is an n-channel metal-oxide-semiconductor transistor.

[0020] In an embodiment of the present invention, the second reset transistor is connected in parallel with the second capacitor.

[0021] In embodiments of the present invention, the bias transistor of each temperature sensing circuit is an n-channel metal-oxide-semiconductor transistor.

[0022] In embodiments of the present invention, the bias transistor of each temperature sensing circuit is a p-channel metal-oxide-semiconductor transistor.

[0023] In an embodiment of the invention, the temperature sensor includes a controller configured to perform processing steps for controlling each temperature sensing circuit. The processing steps include:

[0024] - Disrupt the conductive path between the first and second capacitors.

[0025] - Control the first reset transistor to bias the first capacitor to a first bias voltage, and control the second reset transistor to bias the second capacitor to a second bias voltage.

[0026] - After biasing the first and second capacitors, close the conductive path between the first and second capacitors to distribute charge between them.

[0027] - Read the voltage from the voltage readout node.

[0028] In an embodiment of the invention, the temperature sensor includes an analog-to-digital converter for digitizing the obtained output voltage and a controller configured to convert the digitized output voltage into temperature using a conversion scheme.

[0029] In embodiments of the invention, the controller is configured to use a single-point calibration to obtain a conversion scheme.

[0030] In embodiments of the invention, the controller is configured to use two-point calibration to obtain a conversion scheme.

[0031] In embodiments of the present invention, the capacitance of the first capacitor and the capacitance of the second capacitor are in the range of 20fF to 2000fF.

[0032] In a second aspect, embodiments of the present invention relate to a method for controlling a temperature sensor according to embodiments of the present invention. The method includes:

[0033] - Disrupt the conductive path between the first and second capacitors.

[0034] - Control the first reset transistor to bias the first capacitor to a first bias voltage, and control the second reset transistor to bias the second capacitor to a second bias voltage.

[0035] - After biasing the first and second capacitors, close the conductive path between the first and second capacitors to distribute charge between them.

[0036] - Read the voltage from the voltage readout node.

[0037] Specific and preferred aspects of the invention are set forth in the appended independent and dependent claims. Features from the dependent claims may be suitably combined with features of the independent claims and other dependent claims, and not merely as expressly set forth in the claims.

[0038] These and other aspects of the invention will be apparent from the embodiments described herein, and will be elucidated with reference to the embodiments described herein. Attached Figure Description

[0039] Figure 1 A diagram of a temperature sensing circuit according to an embodiment of the present invention is shown.

[0040] Figure 2 A diagram is shown illustrating a temperature sensing circuit that additionally includes an injection switch according to an embodiment of the present invention.

[0041] Figure 3 A graph showing the time-varying output voltage of a temperature sensing circuit according to an embodiment of the present invention is shown.

[0042] Figure 4 Different signals of a temperature sensing circuit according to an embodiment of the present invention are shown as they change over time.

[0043] Figure 5 The steady-state output voltage of a temperature sensing circuit according to an embodiment of the present invention is shown as a function of temperature.

[0044] Figure 6 The sampled output voltage varies with temperature sensing circuits having different capacitance ratios according to an embodiment of the present invention.

[0045] Figure 7 An electronic schematic diagram of a temperature sensor including a first temperature sensing circuit and a second temperature sensing circuit according to an embodiment of the present invention is shown.

[0046] Figure 8 It shows Figure 7 The output voltage of the temperature sensing circuit changes with temperature.

[0047] Figure 9 A schematic diagram of a temperature sensor including a controller is shown according to an embodiment of the present invention.

[0048] Figure 10 The effect of bias voltage on output voltage in a temperature sensor according to an embodiment of the present invention is illustrated.

[0049] Figure 11 The output voltages of temperature sensing circuits including nMOS bias transistors and pMOS bias transistors are shown.

[0050] Figure 12 One-point calibration and two-point calibration of a temperature sensing circuit according to an embodiment of the present invention are shown.

[0051] Figure 13 Post-processing steps for reducing the power supply voltage-dependent offset in the obtained temperature are shown according to an embodiment of the present invention.

[0052] Figure 14 A post-processing step according to an embodiment of the present invention is shown for making the curvature of a property constant with temperature.

[0053] Figure 15 The temperature error as a function of injection time according to an embodiment of the present invention is shown.

[0054] Any reference numerals in the claims should not be construed as limiting the scope.

[0055] In different accompanying drawings, the same reference numerals refer to the same or similar elements. Detailed Implementation

[0056] The invention will be described with reference to specific embodiments and particular drawings, but the invention is not limited thereto but is defined only by the claims. The described drawings are illustrative only and not restrictive. In the drawings, some elements may be enlarged and not drawn to scale for illustrative purposes. Dimensions and relative dimensions do not correspond to an actual reduction in scale for the practice of the invention.

[0057] The terms "first," "second," etc., used in the specification and claims are used to distinguish between similar elements and are not necessarily used to describe a temporal, spatial, hierarchical, or any other order. It should be understood that such terms are interchangeable where appropriate, and the embodiments of the invention described herein can be operated in a different order than that described or illustrated herein.

[0058] It should be noted that the term "comprising" as used in the claims should not be construed as limiting itself to the means listed thereafter; it does not exclude other elements or steps. Therefore, the term should be interpreted as specifying the presence of the features, integers, steps, or components stated 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 "device comprising means A and B" should not be limited to a device consisting solely of components A and B. It means that for the purposes of this invention, the only relevant components of the device are A and B.

[0059] Throughout this specification, the reference to "an embodiment" or "an embodiment" means that a particular feature, structure, or characteristic described in connection with that embodiment is included in at least one embodiment of the invention. Therefore, the phrase "in an embodiment" or "in an embodiment" appearing in various places throughout this specification does not necessarily refer to the same embodiment, but may refer to different embodiments. Furthermore, in one or more embodiments, as will be apparent to those skilled in the art from this disclosure, particular features, structures, or characteristics may be combined in any suitable manner.

[0060] Similarly, it should be understood that in the description of exemplary embodiments of the invention, various features of the invention are sometimes grouped together in a single embodiment, drawing, or description for the purpose of simplification and to aid in understanding one or more of the various inventive aspects. However, this method of disclosure should not be construed as reflecting an intention to claim more features than are expressly recited in each claim. Rather, as reflected in the appended claims, inventive aspects exist in fewer features than all the features of a single foregoing disclosed embodiment. Thus, the claims appended following the detailed description are thereby explicitly incorporated into this detailed description, wherein each claim itself represents a separate embodiment of the invention.

[0061] Furthermore, while some embodiments described herein include features that are included in other embodiments but not others, it will be understood by those skilled in the art that combinations of features from different embodiments are intended to fall within the scope of the invention and form different embodiments. For example, any embodiment of the claimed embodiments in the appended claims can be used in any combination.

[0062] Numerous specific details are set forth in the description provided herein. However, it should be understood that embodiments of the invention may be practiced without these specific details. In other instances, well-known methods, structures, and techniques have not been shown in detail so as not to obscure the understanding of this description.

[0063] In a first aspect, embodiments of the present invention relate to a temperature sensor based on a switched capacitor. In a preferred embodiment, an integrated differential switched capacitor temperature sensor is proposed.

[0064] The temperature sensor 300 according to an embodiment of the present invention includes at least one temperature sensing circuit 100. An exemplary embodiment of such a temperature circuit is described in... Figure 1The diagram shows a series connection of a first connection node 111 with a first capacitor 110, a bias transistor 140, a second capacitor 150, and a second connection node 151. The temperature sensing circuit can be connected between a first voltage at the first connection node and a second voltage at the second connection node. This can be a regulated voltage or a voltage obtained using one or more resistive voltage dividers. The temperature sensing circuit can be connected between power rails. In this case, the temperature sensing circuit can be connected between the power supply voltage VDD at the first connection node and ground at the second connection node. The advantage is that the voltage difference between nodes 111 and 151 is maximized, and the sensitivity of the temperature sensor circuit is also maximized. The first and second voltages can be symmetrical with respect to the power supply nodes, but this is not strictly required.

[0065] A first capacitor 110 is connected to a first reset transistor 120, which biases the first capacitor to a first bias voltage. Figure 1 In the example, the first bias voltage is voltage V1. This voltage can be, for example, 90% of the supply voltage VDD, or 99% of the supply voltage VDD, or the supply voltage VDD.

[0066] The second capacitor 150 is connected to the second reset transistor 160, which biases the second capacitor 150 to a second bias voltage. Figure 1 In the example, the second bias voltage is voltage V2. This voltage can be, for example, 1% of the supply voltage VDD, or 10% of the supply voltage VDD, or ground voltage GND.

[0067] The first and second bias voltages can be obtained using circuits such as resistive voltage dividers, regulated voltages, or charge pumps. The two capacitors do not strictly need to be biased at the same nominal voltage. For example, one capacitor can be shortened, and the other can be biased with a non-zero charge.

[0068] By controlling the gate of the bias transistor 140, the bias transistor can be turned off, during which time the first and second capacitors can be biased; alternatively, the bias transistor can be turned on to distribute charge between the first and second capacitors. The charge distribution can be controlled by the gate. In embodiments of the invention, the gate of the bias transistor is biased by a bias voltage for distributing charge between the first and second capacitors. This bias voltage can be a predetermined bias voltage.

[0069] In embodiments of the present invention, the transistor has temperature-dependent characteristics. Specifically, the threshold voltage Vt of the bias transistor is temperature-dependent.

[0070] In embodiments of the invention, each temperature sensing circuit includes at least one voltage readout node between a first capacitor 110 and a second capacitor 150. In embodiments of the invention, this could be, for example, a node V between the first capacitor 110 and the bias transistor 140. out (t)(V 输出 (t)). Alternatively, it could be the node V between the bias transistor 140 and the second capacitor 150. x , or any other node between the first capacitor and the second capacitor.

[0071] exist Figure 1 In the exemplary embodiment shown, the bias transistor 140 is an nMOS transistor. A bias voltage V is used. BIAS (V 偏置 The bias transistor is controlled at its gate.

[0072] exist Figure 1 In this configuration, the first reset transistor is a PMOS transistor, with its source connected to a power supply voltage V1 (e.g., VDD) and its drain connected to the second terminal of a first capacitor, where the first terminal is connected to VDD. The gate of the first reset transistor is controlled by a control signal V. RESET (V 复位 )control.

[0073] exist Figure 1 In this configuration, the second reset transistor is an NMOS transistor, with its source connected to the power supply voltage V2 (e.g., GND) and its drain connected to the first terminal of the second capacitor, where the second terminal is connected to GND. The gate of the second reset transistor is controlled by the signal V. EXTRACT (V 提取 )control.

[0074] In embodiments of the invention, the output voltage at the voltage readout node can be obtained relative to ground. However, this is not strictly required. It can also be obtained relative to the output voltage of the voltage readout node of the second temperature sensing circuit.

[0075] In embodiments of the invention, the output voltage can be obtained after the output voltage at the voltage readout node has reached a stable value. This can be a predefined time period, for example, in the range of microseconds, after a bias voltage is applied to the gate of the bias transistor.

[0076] In embodiments of the invention, each temperature sensing circuit 100 includes an injection switch 130 between a first capacitor 110 and a bias transistor 140, or between the bias transistor 140 and a second capacitor 150. The injection switch 130 can be turned on for distributing charge, or turned off when biasing the first or second capacitor. Examples of such temperature sensing circuits are provided below. Figure 2 As shown in the image. (and) Figure 1 compared to, Figure 2 The temperature sensor circuitry in the example additionally includes an injection switch. In this example, the injection switch is an nMOS transistor. The gate of the injection switch uses the injection signal V. INJECT (V 注入 The first capacitor is controlled by a switch. The source of the injection switch is connected to the drain of the bias transistor, and the drain of the injection switch is connected to the second terminal of the first capacitor. The first reset transistor is connected in parallel with the first capacitor (where the source of the first reset transistor is connected to VDD and the drain of the first reset transistor is connected to the second terminal of the first capacitor). The second reset transistor is connected in parallel with the second capacitor (where the source of the second reset transistor is connected to GND and the drain of the second reset transistor is connected to the first terminal of the second capacitor). In this example, the first and second capacitors can be biased at a substantially zero initial voltage. In other words, the initial charge is substantially zero.

[0077] It is important to note that the injection switch is not mandatory. A single bias transistor can be used (i.e., blocking or biasing operation at Vbias).

[0078] In this exemplary embodiment of the invention, the voltage readout node corresponds to the second terminal of the first capacitor.

[0079] In a second aspect, embodiments of the present invention relate to a method for controlling a temperature sensor 300 according to an embodiment of the present invention. The method includes:

[0080] - Disrupt the conductive path between the first and second capacitors.

[0081] - Control the first reset transistor to bias the first capacitor to a first bias voltage, and control the second reset transistor to bias the second capacitor to a second bias voltage.

[0082] - After biasing the first and second capacitors, close the conductive path between the first and second capacitors to distribute charge between them.

[0083] - Read the voltage from the voltage readout node.

[0084] In embodiments of the invention, the conductive path between the first and second capacitors should be interrupted when the first capacitor and the second capacitor are biased. When the voltage readout node is located at the second terminal of the first capacitor, the voltage at the voltage readout node can be read after charge distribution. Reading can be performed before or after the conductive path is interrupted. Reading can even be completed after the second capacitor is biased.

[0085] In embodiments of the present invention, interrupting and closing the conductive path between the first and second capacitors can be achieved by controlling the gate of the injection switch. If there is no injection switch, interrupting and closing the conductive path between the first and second capacitors can be achieved by controlling the gate of the bias transistor.

[0086] Figure 2 The temperature sensing circuit shown can be controlled, for example, in the following ways:

[0087] 1) By using control signal V RESET (t) Force the output voltage at the voltage readout node to its initial state V. OUT (t) = VDD is used to control the first reset transistor to bias the first capacitor.

[0088] 2) Use the control signal V injected at the gate of the switch. INJECT (t) to turn off the injection switch 130 (e.g., within a few microseconds), while simultaneously biasing the bias transistor 140. As a result, the charge will be redistributed between the first and second capacitors according to the following formula: Where C L Let C be the capacitance of the first capacitor. X Let V be the capacitance of the second capacitor. X，peak (V X,峰 The voltage at the readout node after redistribution is the stable voltage. The output voltage varies with time as follows: Figure 3 As shown. The inventor discovered V X，peak It changes substantially linearly with temperature. In embodiments of the invention, the stable voltage V X，peak Sampling by ADC.

[0089] 3) Disrupt the conductive path between the first and second capacitors. Figure 2 In the circuit shown, this can be achieved by using the control signal V. INJECT (t) This is achieved by turning on the injection switch. When the signal goes low, the injection switch is off. When the injection switch is on, the second reset transistor is off. As a result, the second capacitor discharges, and V... OUT(t) Maintain the same potential. Note that this can also be done at the beginning of the cycle. For effective measurement, the first and second capacitors need to be biased to the first and second bias voltages before redistributing the charge in step 2.

[0090] In embodiments of the invention, the temperature measurement process is repeated each time a temperature measurement is required. Between measurements, the temperature sensor is in standby mode, thus achieving lower power consumption.

[0091] Figure 4 It shows the relationship with Figure 2 The circuit operation corresponds to multiple signals that change over time. The following signals are shown from top to bottom: the control signal V for the first reset transistor. res (t)(V 复位 (t)), control signal V of injection switch inj (t)(V 注入 (t)), the control signal V of the second reset transistor ext (t)(V 提取 (t)), the current I injected through the transistor between the first capacitor and the second capacitor. inj (t)(I 注入 (t)), the voltage V at the first terminal of the second capacitor x (t), and the voltage V at the voltage readout node. out (t)(V 输出 (t)).

[0092] Please note that only when V inj When (t) is low, V res (t) and V ext (t) is relatively high. The first or second capacitor is biased only when the injection switch is closed, or more generally when the conductive path between the first and second capacitors is interrupted.

[0093] exist Figure 4 In the two graphs at the bottom, the curves were obtained at different temperatures. It can be seen that the obtained voltage is temperature-dependent. Figure 5 The diagram shows the obtained steady-state voltage as a function of temperature. From... Figure 5 The linear relationship between voltage and temperature at the voltage readout node can be clearly seen.

[0094] The ratio between the capacitances of the second capacitor and the first capacitor (r = C) x / C l This affects the slope of the characteristic. The slope increases with this ratio. Unbound by theory, it is assumed that this slope change is caused by the need to redistribute different amounts of charge and thus transfer different amounts of charge to exit the transistor's saturation region. The change in slope is as follows... Figure 6 As shown in Figure C. x / C l The value changes from 1 to 18 along the direction of the arrow.

[0095] The temperature sensor 300 according to an embodiment of the present invention may include two temperature sensing circuits 100.

[0096] Advantageously, in such a temperature sensor, the ratio of the capacitance of the first capacitor 110 to the capacitance of the second capacitor 150 is different for the two sensing circuits and / or the bias transistor 140 of one temperature sensing circuit is an n-channel MOSFET, and the bias transistor 140 of the other temperature sensing circuit in temperature sensing circuit 100 is a p-channel MOSFET. In the first case, the absolute values ​​of the slopes of the output voltages of the two temperature sensing circuits as a function of temperature will be different; in the second case, the signs of the slopes of the output voltages of the two temperature sensing circuits as a function of temperature will be different. A differential voltage can be obtained between the voltage readout nodes of the two temperature sensing circuits.

[0097] An advantage of embodiments of the present invention is that, compared to a temperature sensing circuit in which the bias transistor is an nMOS transistor, the output voltage at the voltage readout node exhibits an opposite dependence on temperature. As a result, the sensitivity of the differential voltage difference between the output voltages of the two temperature sensing circuits to an increase in temperature can be obtained.

[0098] Figure 7 An electronic schematic diagram of a temperature sensor 300 including a first temperature sensing circuit 100 and a second temperature sensing circuit 100 according to an embodiment of the present invention is shown. In this example, C x，1 / C L，1 <C x，2 / C L，2 . Figure 8 The output voltage V shown varies with the temperature of the first temperature sensing circuit. out，1 (V 输出,1 The output voltage V varies with the temperature of the second temperature sensing circuit. out，2 (V 输出,2 ), and V ou，2 and V out，1 The difference between (V) out，1 -V out，1 By creating a difference between the two output voltages, offset can be removed and sensitivity to temperature changes can be improved.

[0099] In an embodiment of the invention, the temperature sensor 300 includes a controller 200 configured to perform processing steps for controlling each temperature sensing circuit 100. A schematic diagram of such a temperature sensor is shown in... Figure 9 As shown in the diagram. The controller 200 interfaces with temperature sensing circuits 100A and 100B to control the transistor gates and to read the output voltage. The controller is configured to:

[0100] - Disrupt the conductive path between the first and second capacitors. This can be achieved, for example, by controlling the gate of the bias transistor and / or by controlling the gate of the injection switch (if present).

[0101] - Control the first reset transistor to bias the first capacitor to a first bias voltage, and control the second reset transistor to bias the second capacitor to a second bias voltage. This can be achieved by controlling the gate of the first reset transistor and the gate of the second reset transistor.

[0102] - After biasing the first and second capacitors, the conductive path between the first and second capacitors is closed to facilitate charge distribution between them. This can be achieved, for example, by controlling the gate of the bias transistor and / or by controlling the gate of the injection switch (if present).

[0103] - Read the voltage from the voltage readout node. Therefore, the temperature sensor may include an AD converter connected to at least one voltage readout node for digitizing the output voltage and connected to a controller for transmitting the digitized result.

[0104] In embodiments of the invention, the controller is configured to use a conversion scheme to convert a digitized output voltage into a temperature. In embodiments of the invention, the conversion scheme is a linear conversion. In embodiments of the invention, the controller used to convert the digitized output voltage may be the same as the controller used to perform the processing steps.

[0105] In an embodiment of the present invention, the obtained temperature is the temperature of the junction of the bias transistor.

[0106] The controller may be, for example, a microcontroller, a microprocessor, a field-programmable gate array, or any other controller known to those skilled in the art.

[0107] In embodiments of the invention, the first predefined voltage can be determined by the charge applied to the first capacitor. For example, zero charge can be applied to the first capacitor.

[0108] In an embodiment of the present invention, the voltage readout node can be located at the second capacitor (V). x ) at or in the first capacitor (Vout The voltage can be measured relative to a fixed voltage (e.g., VDD or ground), or the voltage at the first capacitor can be measured relative to the voltage at the second capacitor (Vout-Vx).

[0109] In embodiments of the present invention, the temperature sensor may include a voltage regulator for obtaining a predefined voltage for biasing the bias transistor 140.

[0110] In embodiments of the invention, the temperature sensor may include a voltage reference circuit for obtaining a predefined voltage for biasing the bias transistor 140. In embodiments of the invention, this may be a bandgap voltage reference circuit. Figure 10 As shown, the bias voltage V BIAS It has a significant impact on the output voltage's characteristics relative to temperature. Increasing the bias voltage V BIAS This will shift the Vout(T) characteristic downwards and the Vx(T) characteristic upwards. The amount of shift caused depends on the capacitance ratio (C). X / C L ).exist Figure 10 The right-hand diagram shows that the shift was not differentially compensated. V BIAS For every 20mV change, an error of approximately 15℃ will be introduced.

[0111] A temperature sensor according to an embodiment of the invention may include a voltage divider 170 for dividing the voltage at the first connection node 111 to obtain a predefined bias voltage for biasing the bias transistor 140. An advantage of this embodiment is that the bias voltage is implemented as a portion of the supply voltage VDD, resulting in better controlled voltage characteristics relative to temperature. Furthermore, it is advantageous that no external bandgap is required to generate the bias voltage. In embodiments of the invention, the bias voltage may, for example, be equal to the supply voltage divided by two (VDD). BIAS =VDD / 2). The voltage divider can be, for example, a passive voltage divider (e.g., a resistor voltage divider) or an active voltage divider (e.g., a MOSFET voltage divider).

[0112] Figure 11 The left figure shows the sampled output voltage for measurement as a function of temperature, where the bias transistor 140 and injection switch 130 of one temperature sensing circuit in the temperature sensing circuit 100 are n-channel metal-oxide-semiconductor transistors, and the bias transistor 140 and injection switch 130 of the other temperature sensing circuit in the temperature sensing circuit 100 are p-channel metal-oxide-semiconductor transistors. Different lines correspond to different supply voltages. Figure 11The right figure shows the differential voltage between the output voltage of a temperature sensing circuit with an nMOS biased transistor and the output voltage of a temperature sensing circuit with a pMOS biased transistor under the same supply voltage. It can be seen that, regardless of the supply voltage, the characteristics of each differential voltage relative to temperature are the same. In embodiments of the invention, the capacitance ratio of the nMOS and pMOS structures is selected to compensate for their respective shifts. For better matching, the sizes of the corresponding capacitors and transistors in the two temperature sensing circuits can be chosen to be substantially the same. The capacitance of the first capacitor and the capacitance of the second capacitor can, for example, be in the range of 20 fF to 2000 fF, and can be, for example, equal to 200 fF. The width of the MOSFET transistor, WMOSFET, can be in the range of 0.1 μm to 10 μm, and can be, for example, equal to 1.050 μm. The length of the MOSFET transistor, LMOSFET, can be in the range of 0.1 μm to 10 μm, and can be, for example, equal to 0.990 μm.

[0113] In an embodiment of the invention, the controller 200 is configured to obtain a conversion scheme using a single calibration point. An advantage of this embodiment is that calibration at a single calibration point (a single temperature) is sufficient to obtain the conversion scheme. Figure 12 The left figure shows the temperature error of a temperature sensor calibrated using a single-point calibration according to an embodiment of the invention, varying with temperature. Curves FF and SS represent two corner conditions (i.e., conditions with extreme processing parameters). Note that the error at the calibration point is intentionally chosen to be non-zero, but rather positively offset. In this case, the idea is to minimize the error over a large temperature range (-40°C to +175°C) by shifting the curve upwards. Centering the curve at the calibration temperature (i.e., zero error at the calibration temperature) is also an option.

[0114] In an embodiment of the invention, the controller 200 is configured to use two-point calibration to obtain the conversion scheme. An advantage of this embodiment is that the accuracy of the temperature sensor can be improved by using two-point calibration (calibration at two different temperatures). This... Figure 12 As shown in the right-hand figure. Using such calibration, accuracy can be improved by 350%.

[0115] In embodiments of the invention, the controller can be configured to additionally post-process the acquired data to remove power supply voltage-dependent offsets. This is in Figure 13 The left and right graphs show the temperature error as a function of temperature after two-point calibration for different power supply voltages. It can be seen that different offsets are obtained for different power supply voltages. The middle graph shows the relationship between the offset and the power supply voltage. Knowing this relationship allows for the correction of shifts caused by variations in the power supply voltage. This is... Figure 13 As shown in the right figure.

[0116] Additional post-processing steps can be performed to make the curvature of the property constant with temperature (see [link]). Figure 14 The left figure shows the non-constant curvature as a function of temperature. The middle figure shows the voltage error curve as a function of output voltage, and the right figure shows the temperature error after a post-processing step that flattens the temperature-varying curvature using the voltage error as a function of output voltage.

[0117] In embodiments of the invention, the temperature error decreases with increasing injection time. This is in Figure 15 The image is shown in the middle. Figure 15 The figure shows the temperature error as a function of injection time. It evaluates the effect of a 100 ns change in injection time on temperature extraction. As can be seen from the figure, precise timing is not required. This allows for a relaxation of constraints on the time base (e.g., the oscillator).

[0118] The temperature sensor according to embodiments of the present invention can be used for functional safety, for example, by monitoring the operating temperature.

[0119] The surface of the temperature sensor according to embodiments of the present invention can be, for example, less than 5000 μm. 2 or even less than 4000μm 2 .

Claims

1. A temperature sensor (300) for measuring temperature, said temperature sensor (300) comprising at least one temperature sensing circuit (100), characterized in that, Each temperature sensing circuit (100) includes the following items connected in series: - First connection node (111), the first connection node (111) is connected to the first capacitor (110), - The first capacitor (110) is connected to a first reset transistor (120), which is used to bias the first capacitor to a first bias voltage. - A bias transistor (140) is used to distribute charge between the first capacitor and the second capacitor after biasing the first capacitor and the second capacitor. - The second capacitor (150) is connected to a second reset transistor (160), the second reset transistor (160) being used to bias the second capacitor to a second bias voltage, wherein the bias transistor (140) is arranged between the first capacitor (110) and the second capacitor (150). - A second connection node (151) is connected to the second capacitor (150), wherein the first connection node (111) and the second connection node (151) are configured to apply a power supply voltage between the first connection node (111) and the second connection node (151). Each temperature sensing circuit includes at least one voltage readout node between the first capacitor (110) and the second capacitor (150) for outputting a voltage as a temperature measurement.

2. The temperature sensor (300) as claimed in claim 1, wherein the temperature sensor (300) comprises two temperature sensing circuits (100), characterized in that, The ratio of the capacitance of the first capacitor (110) to the capacitance of the second capacitor (150) is different for the two sensing circuits and / or the bias transistor (140) of one of the temperature sensing circuits is an n-channel metal-oxide-semiconductor transistor, and the bias transistor (140) of the other temperature sensing circuit in the temperature sensing circuit (100) is a p-channel metal-oxide-semiconductor transistor.

3. The temperature sensor (300) of claim 1, wherein the temperature sensor (300) includes a voltage reference circuit for obtaining a predefined bias voltage for biasing the bias transistor (140).

4. The temperature sensor (300) of claim 1, wherein the temperature sensor (300) includes a voltage divider (170) for dividing the voltage at the first connection node (111) to obtain a predefined bias voltage for biasing the bias transistor (140).

5. The temperature sensor (300) as described in claim 1, characterized in that, Each temperature sensing circuit (100) includes an injection switch (130) between the first capacitor (110) and the bias transistor (140) or between the bias transistor (140) and the second capacitor (150), wherein the injection switch (130) can be turned on to distribute the charge or turned off when the first capacitor or the second capacitor is biased.

6. The temperature sensor (300) as described in claim 1, characterized in that, The first reset transistor (120) of each temperature sensing circuit (100) is a p-channel metal-oxide-semiconductor transistor.

7. The temperature sensor (300) as described in claim 1, characterized in that, The second reset transistor (160) of each temperature sensing circuit (100) is an n-channel metal-oxide-semiconductor transistor.

8. The temperature sensor (300) as described in claim 1, characterized in that, The bias transistor (140) of each temperature sensing circuit (100) is an n-channel metal-oxide-semiconductor transistor.

9. The temperature sensor (300) as claimed in claim 1, characterized in that, The bias transistor (140) of each temperature sensing circuit (100) is a p-channel metal-oxide-semiconductor transistor.

10. The temperature sensor (300) of claim 1, wherein the temperature sensor includes a controller (200) configured to perform processing steps for controlling each temperature sensing circuit (100), the processing steps including: - Disrupt the conductive path between the first capacitor and the second capacitor. - Control the first reset transistor to bias the first capacitor to the first bias voltage, and control the second reset transistor to bias the second capacitor to the second bias voltage. - After biasing the first capacitor and the second capacitor, the conductive path between the first capacitor and the second capacitor is closed to distribute charge between the first capacitor and the second capacitor. - Read the voltage from the voltage readout node.

11. The temperature sensor (300) of claim 1, wherein the temperature sensor includes an analog-to-digital converter for digitizing the obtained output voltage and a controller (200) configured to convert the digitized output voltage into temperature using a conversion scheme.

12. The temperature sensor (300) as claimed in claim 11, characterized in that, The controller (200) is configured to use a single-point calibration to obtain the conversion scheme.

13. The temperature sensor (300) as claimed in claim 11, characterized in that, The controller (200) is configured to use two-point calibration to obtain the conversion scheme.

14. The temperature sensor (300) as claimed in claim 1, characterized in that, The capacitance of the first capacitor (110) and the capacitance of the second capacitor (150) are in the range of 20fF to 2000fF.

15. A method for controlling a temperature sensor (300) as described in any of the preceding claims, the method comprising: - Disrupt the conductive path between the first capacitor and the second capacitor. - Control the first reset transistor to bias the first capacitor to the first bias voltage, and control the second reset transistor to bias the second capacitor to the second bias voltage. - After biasing the first capacitor and the second capacitor, the conductive path between the first capacitor and the second capacitor is closed to distribute charge between the first capacitor and the second capacitor. - Read the voltage from the voltage readout node.

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