Thermal sensors and temperature measurement methods

Abstract

An embodiment of the present invention provides a thermal sensor comprising: a first temperature-sensitive device that generates a first temperature-dependent signal, wherein each of two branch circuits of the first temperature-sensitive device includes a bandgap thermal sensing device and a current source, and each bandgap thermal sensing device is adapted to generate a signal in response to a current passing through the bandgap thermal sensing device; a second temperature-sensitive device that generates a second temperature-dependent signal, wherein the second temperature-sensitive device includes a single bandgap thermal sensing device and a current source, and the single bandgap thermal sensing device is adapted to generate a signal in response to a current passing through the single bandgap thermal sensing device; and a signal processing circuit connected to the two branch circuits of the first temperature-sensitive device and adapted to process the received first temperature-dependent signal to generate a first processed signal, wherein the thermal sensor generates an output signal based on the first processed signal and the second temperature-dependent signal. Embodiments of the present invention also relate to a method for temperature measurement.

Description

[0001] Divisional application

[0002] This application is a divisional application of patent application number 201910931842.1 entitled “Thermal sensor and method for temperature measurement” filed on September 29, 2019. Technical Field

[0003] Embodiments of the present invention relate to thermal sensors and methods of temperature measurement. Background Art

[0004] The present invention relates generally to thermal sensors and more particularly to reducing temperature errors in thermal sensors.

[0005] Thermal sensors have a wide range of uses. For many applications, their accuracy is important, even critical. Calibration of thermal sensors at only one or a limited number of temperatures can make it difficult to ensure their accuracy across the entire intended range of applications due to deviations from the ideal sensor characteristics. Efforts are underway to improve the accuracy of thermal sensors. Summary of the Invention

[0006] An embodiment of the present invention provides a thermal sensor, comprising: a first temperature-sensitive device, suitable for generating a first temperature-dependent signal; a second temperature-sensitive device, suitable for generating a second temperature-dependent signal; and a signal processing circuit, operably connected to receive the first temperature-dependent signal and the second temperature-dependent signal from the first temperature-sensitive device and the second temperature-sensitive device, and suitable for processing the received signals using processing parameters different from each other to generate a first processing signal and a second processing signal, respectively, and generating an output signal based on the first processing signal and the second processing signal.

[0007] Another embodiment of the present invention provides a method for temperature measurement, comprising: generating a first current density in a first thermal sensing device set at a temperature T; generating a second current density in a second thermal sensing device set at T, the second current density being different from the first current density; generating a third current density in a third thermal sensing device set at T; generating a fourth current density in a fourth thermal sensing device set at T, the fourth current density being different from the third current density; obtaining a first differential voltage between a first voltage generated by the first thermal sensing device in response to the first current density and T on the one hand and a second voltage generated by the second thermal sensing device in response to the second current density and T on the other hand; obtaining a second differential voltage between a third voltage generated by the third thermal sensing device in response to the third current density and T on the one hand and a fourth voltage generated by the fourth thermal sensing device in response to the fourth current density and T on the other hand; obtaining a third differential voltage dV between the first differential voltage multiplied by a first gain factor and the second differential voltage multiplied by a second gain factor, the second gain factor being different from the first gain factor; and determining T based on the third differential voltage.

[0008] Yet another embodiment of the present invention provides a method for temperature measurement, comprising: generating a first current density in a first thermal sensing device set at a temperature T to generate a first voltage in response to the first current density and T; generating a second current density in a second thermal sensing device set at T to generate a second voltage in response to the second current density and T, wherein the second current density is different from the first current density; obtaining a differential voltage dV between the first voltage multiplied by a first gain factor and the second voltage multiplied by a second gain factor, wherein the second gain factor is different from the first gain factor; and determining T based on the differential voltage. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Various aspects of the present invention are best understood from the following detailed description when read in conjunction with the accompanying drawings. It should be emphasized that, in accordance with standard practice in the industry, various components are not drawn to scale and are used for illustrative purposes only. In fact, the dimensions of various components may be arbitrarily increased or decreased for clarity of discussion.

[0010] Figure 1A The thermal sensor schematically illustrates components in a thermal sensor according to one aspect of the present invention.

[0011] Figure 1B According to one aspect of the present invention Figure 1A A graphical representation of the ideal and actual voltage-temperature relationship for each component thermal sensor.

[0012] Figure 2Ais a graphical representation of voltage-temperature relationships across an operating temperature range approximating an assembly thermal sensor in accordance with one aspect of the present invention.

[0013] Figure 2B Shown is a modified relative voltage-temperature relationship for two component thermal sensors with matching offsets according to one aspect of the present invention.

[0014] Figure 3 A discrete timing type thermal sensor circuit according to one aspect of the present invention is schematically shown.

[0015] Figure 4 A continuous DC type thermal sensor circuit according to one aspect of the present invention is schematically shown.

[0016] Figure 5 A continuous DC type thermal sensor circuit with differential feedback according to one aspect of the present invention is schematically illustrated.

[0017] Figure 6 A continuous DC type thermal sensor circuit with single-ended feedback according to one aspect of the present invention is schematically shown.

[0018] Figure 7 Shown Figure 6 Temperature performance data for a prototype thermal sensor of the type shown in Figure 2 at various process corners.

[0019] Figure 8A The voltage-temperature relationship of two transistors in a differential current density thermal sensor according to one aspect of the present invention and partial slope adjustment of the voltage-temperature relationship of one of the transistors are shown.

[0020] Figure 8B Shown with Figure 8A The differential voltage-temperature relationship of the thermal sensor is shown in Figure 2.

[0021] Figure 9 A discrete clocked thermal sensor circuit with partial slope adjustment according to one aspect of the present invention is schematically illustrated.

[0022] Figure 10 A continuous DC type thermal sensor circuit with resistance ratio partial slope adjustment according to one aspect of the present invention is schematically illustrated.

[0023] Figure 11 A continuous DC type thermal sensor circuit with resistance ratio and operational amplifier-driver section slope adjustment according to one aspect of the present invention is schematically illustrated.

[0024] Figure 12 Schematically shows a V beReplicate some of the slope-adjusted continuous DC thermal sensor circuits.

[0025] Figure 13 A switched single transistor branch thermal sensor circuit with partial slope adjustment controlled by a digital control unit (eg, a microcontroller ("MCU")) according to one aspect of the present invention is schematically illustrated.

[0026] Figure 14 Shown Figure 11 Temperature performance data at the process corner for a prototype thermal sensor of the type shown in .

[0027] Figure 15 Schematically shows a continuous DC type thermal sensor circuit with differential feedback according to one aspect of the present invention, similar to Figure 5 The circuit is the same as that shown in , but with the bipolar junction transistors replaced by field effect transistors.

[0028] Figure 16 A method of temperature measurement according to one aspect of the present invention is summarized. DETAILED DESCRIPTION

[0029] The following disclosure provides many different embodiments or examples for implementing the different features of the present invention. Specific embodiments or examples of components and arrangements are described below to simplify the present invention. These are, of course, merely examples and are not intended to be limiting. For example, in the following description, forming a first component above or on a second component may include embodiments in which the first component and the second component are formed in direct contact, and may also include embodiments in which additional components may be formed between the first component and the second component so that the first component and the second component may not be in direct contact. As used herein, forming a first component on a second component refers to forming a first component in direct contact with the second component. In addition, the present invention may repeat reference numbers and / or letters in various examples. This repetition is for the purpose of simplicity and clarity and does not, in itself, indicate a relationship between the various embodiments and / or configurations discussed.

[0030] Thermal sensors, or temperature sensors, are widely used in a variety of applications. For example, thermal sensors are used in integrated circuits, such as memory modules, to monitor and control the temperature of the integrated circuits to ensure their proper operation. Examples of thermal sensors include sensors that employ bipolar junction transistors ("BJTs"), which measure the voltage between a pair of their terminals (such as the base-emitter voltage or V BE ) has a certain temperature dependence, which has certain characteristics, such as exponential dependence under ideal (theoretical) conditions. Deviations from the ideal characteristics will lead to temperature measurement errors. Certain embodiments disclosed herein have lower temperature errors than traditional thermal sensors

[0031] In some embodiments, the temperature sensor includes two pairs of BJTs. In each pair, the two BJTs have different current densities, either by passing the same current through two BJTs of different sizes, or by passing different currents through two BJTs of the same size, or a combination of both methods. Each BJT generates V BE As a result, the differential V in each pair is obtained. BE (dV BE or ΔV BE ) or two V BE The difference between the two pairs of dV BE The difference between the two pairs is used as the output signal. BE can be amplified differently so that dV BE have substantially the same offset value (S1) in a parameter, such as an offset voltage at a reference temperature (e.g., 0 K), where the offset voltage can be defined as dV at a calibration point (e.g., 25°C). BE The tangent of the temperature curve (or dV within the operating temperature range BE The offset voltage at the reference temperature is calculated based on some other linear approximation of the voltage-temperature curve. Other forms of approximation of the voltage-temperature relationship can also be used. Other types of transistors (such as MOSFETs) can be used instead of BJTs.

[0032] In some embodiments, a single pair of BJTs may be used, but V may be amplified differently. BE , so that the amplified V BE The temperature profiles are closely matched over the expected operating temperature range.

[0033] refer to Figure 1A , two BJT pairs (110, 140) are configured to generate dV BE (dV BE1 and dV BE2 ), which will be combined to provide a voltage signal that more closely resembles a more ideal temperature dependence than either BJT pair (110, 140). The more ideal temperature dependence can be achieved, for example, by a linear dependence, where the voltage is substantially proportional to absolute temperature ("PTAT"), such that a single-point temperature calibration (e.g., at 25°C) is sufficiently reliable for temperature sensing over the entire expected temperature range (e.g., from about -50°C to about 150°C, from -40°C to about 125°C, from about -25°C to about 110°C, or from about 0°C to about 100°C) for operation of the electronic device.

[0034] Figure 1AEach BJT pair (110, 140) in the example shown in FIG comprises two branches connected in parallel to each other (120, 130 in pair (110) and (150, 160) in pair (140)). Each branch comprises a current source (122, 132, 152, 162) connected in series with a diode-connected transistor (124, 134, 154, 164), respectively. The base and collector in each diode-connected transistor are connected to each other and to a common reference point (ground in this example); the emitter is connected to the current source.

[0035] Each diode-connected transistor (124, 134, 154, 164) is designed to operate at its respective emitter current density. The current density in each diode-connected transistor is determined by the current in the corresponding branch and the cross-sectional area n, m, p, or q of the emitter-base junction ("emitter region") of the diode-connected transistor. Thus, different current densities can be generated by currents of different magnitudes from the current sources (122, 132, 152, 162), where the cross-sectional area of ​​the emitter-base junctions in the diode-connected transistors (124, 134, 154, 164) is the same. Different current densities can also be generated by currents of the same magnitude from the current sources (122, 132, 152, 162), but with different emitter regions n, m, p, and q for the diode-connected transistors (124, 134, 154, 164), respectively. In another alternative, different current densities may be generated by different magnitudes of current from current sources (122, 132, 152, 162) where the cross-sectional areas of the emitter-base junctions in diode-connected transistors (124, 134, 154, 164) are different.

[0036] Given different current densities in the two branches of each BJT pair (110, 140), a differential voltage is generated between the emitters of the two diode-connected transistors in the BJT pair as a function of the temperature to which the two diode-connected transistors are exposed. Thus, a differential voltage dV is generated between the emitters of the diode-connected transistors (124, 134). BE1 ; A differential voltage dV is generated between the emitters of the diode-connected transistors (154, 164) BE2 .

[0037] Reference Figure 1B , for each BJT pair (110, 140), the differential base-emitter voltage (dV BE1 or dV BE2 ) makes it temperature dependent. The differential base-emitter voltage (dV BE (=dV BE1 or dV BE2The relationship between )) and current density,

[0038]

[0039] where T is the absolute temperature of the BJT pair, η is the ideality factor, k is the Boltzmann constant, q is the electron charge, and r is the ratio between the emitter current densities in the BJT pair, With equal currents in both legs of each BJT pair, r = n / m and r = p / q.

[0040] For an ideal thermal sensor, where η is a constant for all temperatures, C is a constant, and V BE Proportional to absolute temperature T, dV BE The curve as a function of temperature is a straight line through the origin, that is, at T = 0K dV BE =0V. Therefore, for the BJT pair (110, 140), the ideal dV BE1 -T and dV BE2 -T curves will be Figure 1B The straight line (170, 180) in the figure is shown in Figure 1. However, in practical thermal sensors, the ideality factor η usually does not change with temperature. Therefore, dV BE The -T relationship is generally not linear, as shown by curves (172, 182) for BJT pairs (110, 140), respectively.

[0041] refer to Figure 2A , and using the BJT pair (140) as an example, for an ideal BJT pair, dV BE2 The PTAT relationship will result in dV BE2 -T graph, as described above. In this case, a single-point calibration (i.e., by measuring dV at a single temperature (such as 25°C) BE2 Calibration) will result in accurate temperature measurements because a single constant, C (or the slope of the line (210)), is required to determine dV at all temperatures. BE2 However, since C is usually not constant with temperature, the actual dV BE2 A -T plot is typically a curve, such as the conceptually shown curve (182). Consequently, a single point calibration (e.g., at 25°C) will result in errors at temperatures far from the calibration point, in some cases significant (e.g., ε1 at -40°C and ε2 at 125°C).

[0042] In practical applications, the calibration accuracy of the temperature sensor only relates to the expected operating temperature range, such as about 40°C to about 125°C. According to certain aspects of the present invention, the differential base-emitter voltages from the two BJT pairs (110, 140) can be appropriately combined to obtain a signal that is substantially PTAT at least within the expected operating temperature range, so that a single-point calibration is sufficient for the expected operation of the electronic device. For example, Figure 2A dV BE2 The -T curve (182) can be well approximated by a straight line (220) over a temperature range of about 40°C to about 125°C. The straight line (220) can be based on any approximation method that results in an error within an acceptable level over the expected operating temperature range. For example, the line (220) can be the dV at the calibration temperature (e.g., 25°C). BE2 -T curve; in another example, line (220) is a line connecting the two ends of the segment of curve (182) within the expected temperature range (e.g., at -40°C and 125°C); in another example, line (220) can be a least squares fit to the curve within the expected temperature range.

[0043] Similarly, if dV BE1 -T curve (172) shows that it can be BE2 -T curve (182) is approximated by a straight line (not shown in the figure) within the same temperature range. In this case, dV BE2 The line (220) of the -T curve (182) has an intersection S1 on the y-axis (ie, 0K); in this case, dV BE1 The line of the -T curve (172) has an intersection S2 on the y-axis. According to aspects of the present invention, dV BE1 It can be amplified by a factor M (which can be greater, equal to or less than 1) so that M·S2=S1. Figure 2B As shown, the line (280) of the approximately magnified differential voltage curve (272) is M×dV BE1 With dV BE2 -T curve (182) has the same intersection S1. Differential voltage dV BE12 It is in this form,

[0044] dV BE12 =M·dV BE1 -dV BE2 ≈CT+M·S2-C″T-S1=(C′-C″)T,

[0045] Where C' and C" are constants. Therefore, the combined differential voltage is essentially PTAT, and a thermal sensor that produces such a differential voltage is suitable for single-point calibration. That is, the differential voltage value dV0 and the dV at a single known temperature T0 (for example, 25°C (or 298K)) can be obtained. BE12 , the temperature T can be determined as T = d V • T0 / dV0, where T and T0 are measured in K.

[0046] dV BE12 =M·dV BE1 -N·dV BE2 ,

[0047] Basically it's PTAT signaling.

[0048] Therefore, in order to obtain a substantially PTAT signal in temperature measurement, according to some embodiments, the following steps may be taken: generating a first current density in a first thermal sensing device set at a temperature T (1610); generating a second current density in a second thermal sensing device set at T, the second current density being different from the first current density (1620); generating a third current density in a third thermal sensing device set at T (1630); generating a fourth current density in a fourth thermal sensing device set at T, the fourth current density being different from the third current density (1640); generating a first current density in the first thermal sensing device in response to the first current density and T on the one hand, and generating a second current density in the second thermal sensing device in response to the first current density and T on the other hand. Obtaining a first differential voltage (1650) between the generated first voltage and a second voltage generated by the second thermal sensing device in response to the second current density and T on the one hand; obtaining a second differential voltage (1660) between a third voltage generated by the third thermal sensing device in response to the third current density and T on the one hand and a fourth voltage generated by the fourth thermal sensing device in response to the fourth current density and T on the other hand; obtaining a third differential voltage dV between the first differential voltage multiplied by a first gain factor and the second differential voltage multiplied by a second gain factor, the second gain factor being different from the first gain factor (1670); and determining T based on the third differential voltage (1680).

[0049] refer to Figure 3According to one aspect of the present invention, a thermal sensor circuit (300) implements the above-mentioned scheme for obtaining a basic PTAT thermal sensor. In this example, the circuit (300) is a discrete timing type circuit. It includes the above-mentioned BJT pair (110, 140) and a signal processing circuit, in this example, the signal processing circuit is a pair of switched capacitor amplifiers (310, 340). The switched capacitor amplifier (310) includes an operational amplifier (312), an input capacitor (314), a feedback capacitor (316) and switches (318, 320, 322), and the switches can be any suitable switching devices, including switching transistors. Similarly, the switched capacitor amplifier (340) includes an operational amplifier (342), an input capacitor (344), a feedback capacitor (346) and switches (348, 350, 352), and the switches can be any suitable switching devices, including switching transistors. The switch inputs of the amplifier (310) are connected to the respective emitters of the diode-connected transistors (124, 134) to receive the differential signal dV BE1 , dV BE1 is the voltage V at the emitter of the diode-connected transistor (124) BE1a The voltage V at the emitter of the diode-connected transistor (134) BE1b Similarly, the switch inputs of the amplifier (340) are connected to the respective emitters of the diode-connected transistors (154, 164) to receive the differential signal dV BE2 , the differential signal dV BE2 is the voltage V at the emitter of the diode-connected transistor (154) BE2a The voltage V at the emitter of the diode-connected transistor (164) BE2b The difference between .

[0050] In one example, the amplifiers (310, 340) have gains M and N, respectively, where M·S2-NS1=0, where S1 and S2 are approximately dV over the expected operating temperature range (e.g., from about 40°C to about 125°C). BE2 -T curve (182) and dV BE1 -Y-intersection of the line of the T curve (172). As mentioned above, the differential output signal dV BE12 is substantially proportional to absolute temperature within the expected operating temperature range.Thus, the thermal sensor (300) is susceptible to single-point calibration.

[0051] As used in this disclosure, "gain" or "amplification" means the factor by which a signal input to a circuit (an "amplifier") is multiplied to generate an output of the circuit; the factor is not limited to a number greater than 1.

[0052] Other discrete clocked type circuits may also be used, such as switched capacitor sample / hold circuits.

[0053] The signal processing circuit for obtaining different gains of the two BJT pairs can be of any type suitable for this purpose. For example, a continuous DC type circuit can also be used. For example, in Figure 4 In the example, a continuous DC amplifier (400) can be used instead of Figure 3 The switched capacitor amplifiers (310, 340) shown are shown. The amplifier (400) includes a pair of summing amplifiers (410, 430) and a differential amplifier (450). The first summing amplifier (410) includes an operational amplifier (412), two input resistors (414, 416) and a feedback resistor (418). Similarly, the second summing amplifier (430) includes an operational amplifier (432), two input resistors (434, 436) and a feedback resistor (438). The differential amplifier (450) includes a pair of operational amplifiers (452, 454), an input resistor (456) and a feedback resistor (458) associated with the operational amplifier (452), and an input resistor (460) and a feedback resistor (462) associated with the operational amplifier (454). The summing amplifiers (410, 430) receive two pairs of inputs: the V BE1a and V BE2b , and V of the amplifier (430) BE2a and V BE1b The output of the summing amplifiers (410, 430) is the input of the differential amplifier (450). The output ΔV of the differential amplifier (450) is the input V BE1a 、V BE2b 、V BE2a and V BE1b By properly choosing the resistance value of the resistor, ΔV can be set to dV BE1 and dV BE2 For example, for Figure 4 The symbolized resistance value is R1=R2=R3=R4, ΔV=M·dV BE1 -dV BE2 , where M is a value that makes ΔV substantially proportional to absolute temperature (eg, M·S2-S1=0).

[0054] refer to Figure 5According to another aspect of the present invention, a thermal sensor circuit (500) includes two branches of BJT pairs (510, 540). The first BJT pair (510) includes a pair of diode-connected transistors (524, 534) and current bias transistors M1 (522), M2 (526), ​​M3 (532), and M4 (536), wherein the designations "M1," "M2," "M3," and "M4" also represent dimensions, such as channel width, of the respective transistors (522, 526, 532, 536). Similarly, the second BJT pair (540) includes a pair of diode-connected transistors (554, 564), and current bias transistors M5 (552), M6 (556), M7 (562), and M8 (566), where the labels "M5," "M6," "M7," and "M8" also represent the dimensions, such as channel width, of the respective transistors (552, 556, 562, 566). Transistors M1-M8 in this example are field effect transistors (FETs), such as metal oxide semiconductor field effect transistors (MOSFETs), but may be any suitable type of transistor. The emitter of the first diode-connected transistor (524) in the first branch (510) is directly connected to the drains of transistors M2 (526) and M5 (552); the emitter of the first diode-connected transistor (554) in the second branch (540) is directly connected to the drains of transistors M6 (556) and M1 (522). The emitter of the second diode-connected transistor (534) in the first branch (510) is connected to the drains of transistors M3 (532) and M8 (566) via resistor R1 (538). The emitter of the second diode-connected transistor (564) in the second branch (540) is connected to the drains of transistors M7 (562) and M4 (536) via resistor R2 (568).

[0055] Each branch (510, 540) is associated with a corresponding amplifier (570, 580). The input to the first amplifier (570) is the differential voltage dV between the emitters of the diode-connected transistors (524, 534) through a resistor R1 (538). BE1 The input to the second amplifier (580) is the differential voltage dV between the emitters of the diode-connected transistors (554, 564) through resistor R2 (568). BE2 The output of the first amplifier (570) is connected to the control electrodes (gates in this example) of transistors M1 (522), M2 (526), ​​M3 (532) and M4 (536); the output of the second amplifier (580) is connected to the control electrodes (gates in this example) of transistors M5 (552), M6 (556), M7 (562) and M8 (566).

[0056] The first output V of the thermal sensor (500) out1 Provided at a junction between the first output resistor R4 (598) and the drain of the first output transistor M10 (596); a second output V of the thermal sensor (500) out2 Provided at the junction between the second output resistor R3 (594) and the drain of the second output transistor M9 (592). The control electrode (gate in this example) of the first output transistor M10 (596) is connected to the control electrodes of transistors M1 (522), M2 (526), ​​M3 (532) and M4 (536); the control electrode (gate in this example) of the second output transistor M9 (592) is connected to the control electrodes of transistors M5 (552), M6 (556), M7 (562) and M8 (566). The source electrodes of transistors M1 to M10 are connected together. Transistor M10 and resistor R4 form a first current mirror with transistor M1, generating a voltage output V from resistor R4. out1 , and generates a mirror current of current I2 through transistor M1. Similarly, transistor M9 and resistor R3 form a second current mirror with transistor M8, generating a voltage output V from resistor R3. out2 and generates a mirror current of current I1 through transistor M8.

[0057] In this example, the output V out1 and V out2 Each is dV BE1 and dV BE2 function, each dV BE1 and dV BE2 is a function of the current density ratio in the BJT pair (510, 540). Figure 3 Similar to the configuration shown, the current density ratio in each BJT pair can be set by the same BJT size (n=m; p=q), but by transistors M2 and M3 (for BJT pair (510)) (I M2 :I M3 ), or M6 and M7 (for BJT pair (540)(I M6 :I M7 ) are not consistent. Optionally, the current density ratio in each BJT pair can be controlled by transistors M2 and M3 (I M2 :I M3 =1) or M6 and M7 (I M6 :I M7 =1) but with different BJT sizes. A combination of the two configurations described above (ie, different BJT sizes and transistor currents) can also be used.

[0058] Current ratio I M2 :I M3 and IM6 :I M7 Then they are dV BE1 R1 and dV BE2 The current ratio is in turn a function of the W / L ratio between transistors M1 and M2, M4 and M3, M5 and M6, and M8 and M7, where the W / L ratio of a transistor is the aspect ratio (width:length) of the transistor's channel. In one example, the W / L ratio between transistors M1 and M2 and between transistors M4 and M3 is 1:m; the W / L ratio between transistors M5 and M6 and between transistors M8 and M7 is 1:k. In this configuration, the output V out1 is k1(m1dV BE1 -dV BE2 ), where k1 and m1 are functions of R1, R2, m, k, and R4; similarly, the output V out2 is k2(m2dV BE2 -dV BE1 ), where k2 and m2 are functions of R1, R2, m, k, and R3. Therefore, by properly choosing the resistor values ​​R1, R2, R3, and R4 and the ratios m and k, dV BE2 and / or dV BE1 The voltage offset is used to generate a PTAT voltage suitable for single-point calibration.

[0059] refer to Figure 6According to another aspect of the present invention, a thermal sensor circuit (600) includes two branches of BJT pairs (610, 640). The first BJT pair (610) includes a pair of diode-connected transistors (624, 634) and current bias transistors M1 (522), M2 (626), and M3 (632), wherein the labels "M1," "M2," and "M3" also represent the dimensions of the respective transistors (622, 626, 632), such as the channel width. Similarly, the second BJT pair (640) includes a pair of diode-connected transistors (654, ​​664) and current bias transistors M4 (656), M5 (662), and M6 (666), wherein the labels "M4," "M5," and "M6" also represent the dimensions of the respective transistors (656, 662, 666), such as the channel width. Transistors M1-M6 in this example are field effect transistors (FETs), such as metal oxide semiconductor field effect transistors (MOSFETs), but may be any suitable type of transistor. The emitter of the first diode-connected transistor (624) in the first branch (610) is directly connected to the drains of transistors M2 (626) and M6 (666); the emitter of the first diode-connected transistor (654) in the second branch (640) is directly connected to the drain of transistor M4 (656). The emitter of the second diode-connected transistor (634) in the first branch (610) is connected to the drain of transistor M3 (632) through resistor R1 (638); the emitter of the second diode-connected transistor (664) in the second branch (640) is connected to the drains of transistors M5 (662) and M1 (622) through resistor R2 (668).

[0060] Each branch (510, 540) is associated with a corresponding amplifier (670, 680). The input to the first amplifier (670) is the differential voltage dV between the emitters of the diode-connected transistors (624, 634) through a resistor R1 (638). BE1 The input to the second amplifier (680) is the differential voltage dV between the emitters of the diode-connected transistors (654, ​​664) through resistor R2 (668). BE2 The output of the first amplifier (570) is connected to the control electrodes (gates in this example) of transistors M1 (622), M2 (626), and M3 (632); the output of the second amplifier (680) is connected to the control electrodes (gates in this example) of transistors M4 (656), M5 (662), and M6 (666).

[0061] The first output V of the thermal sensor (600) out1Provided at a junction between the first output resistor R4 (698) and the drain of the first output transistor M7 (696); a second output V of the thermal sensor (600) out2 Provided at the junction between the second output resistor R3 (694) and the drain of the second output transistor M8 (692). The control electrode (gate in this example) of the first output transistor M7 (696) is connected to the control electrodes of transistors M1 (622), M2 (626) and M3 (632); the control electrode (gate in this example) of the second output transistor M8 (692) is connected to the control electrodes of transistors M4 (656), M5 (662) and M6 (666). The source electrodes of transistors M1 to M8 are connected together. Transistor M7 and resistor R4 form a first current mirror with transistor M1, generating a voltage output V from resistor R4. out1 , and generates a mirror current of current I2 through transistor M1. Similarly, transistor M8 and resistor R3 form a second current mirror with transistor M6, generating a voltage output V from resistor R3. out2 , and generates a mirror current of the current I1 through the transistor M6.

[0062] In this example, the output V out1 and V out2 Each is dV BE1 and dV BE2 function, each dV BE1 and dV BE2 is a function of the current density ratio in the BJT pair (610, 640). Figure 3 and Figure 5 Similar to the configuration shown in , the current density ratio in each BJT pair can be determined by the BJT size (n / m; p / q) and the current density ratio through transistors M1, M2 and M3 (for BJT pair (610)) (I M1 :I M2 :I M3 ), or M4, M5 and M6 (for BJT pair (640))(I M4 :I M5 :I M6 ) is set by combining the ratios of the currents. The current ratios are dV BE1 R1 and dV BE2 The current ratio is in turn a function of the ratio of the W / L ratios between transistors M1, M2 and M3, and between M4, M5 and M6. Figure 5 Similar to the configuration shown, Figure 6 In the configuration, the output V out1 k1(m1dV BE1 -dV BE2), where k1 and m1 are functions of the W / L ratios of R1, R2, and R4, and M1, M2, and M3; similarly, the output V out2 is k2(m2dV BE2 -dV BE1 ), where k2 and m2 are functions of the W / L ratios of R1, R2, R3, and M4, M5, and M6. Therefore, by appropriately selecting the resistor values ​​R1, R2, R3, and R4 and the W / L ratios, dV BE2 and / or dV BE1 The voltage offset is used to generate a PTAT voltage suitable for single-point calibration. For example, Figure 7 Shown Figure 6 The temperature error of several process corners (TT, FF, and SS) of the thermal sensor is shown as a function of temperature. Single-point calibration is performed at 25°C. The temperature error is within about 3°C ​​over the temperature range of -25°C to 110°C. In other words, in dV BE12 -T in the figure by (T = 0K, dV BE12 =0V) and (T = 273K + 25K, dV BE12 The temperature determined by the straight (PTAT) line at 25°C does not differ from the actual temperature by more than 3°C. More generally, if the temperature is determined by the line passing through (T = 0K, dV BE12 =0V) and the straight (PTAT) line at dV BE12 - calibration point in the T curve (e.g., T = 273K + 25K, dV BE12 The output of the thermal sensor is essentially PTAT if the temperature determined at 25°C does not differ from the actual temperature by more than an amount (e.g., 3, 2, or 1°C) that is considered acceptable for proper operation of the device (e.g., an integrated circuit) within the expected temperature range.

[0063] In another aspect of the invention, instead of combining the output signals of two transistor pairs to achieve a more linear temperature dependence, the temperature-dependent voltages from two individual transistors can be appropriately combined to obtain a more linear signal (temperature) than a single transistor. For example, in one aspect of the invention, with respect to the V BE , the base-emitter voltage (V BE ) to produce a signal that is more linear with absolute temperature.

[0064] like Figure 8A As shown, each transistor in a BJT pair, such as Figure 1A The BJT pair (110) shown in FIG. 1 generates a temperature-dependent V BE Thus, for example, the voltage V at the emitter of the diode-connected transistor (124) BE1 With VBE Temperature curve (810), and the voltage V at the emitter of the diode-connected transistor (134) BE2 With V BE Temperature curve (820). Figure 8B As shown, the differential voltage dV BE (840) may deviate significantly from the ideal PTAT temperature dependence (850), except at or near the calibration point (e.g., 25°C). However, according to one aspect of the present invention, V BE1 and V BE3 To achieve a more linear dV BE For example, in one embodiment, relative to V BE2 Adjust (e.g., by amplifying) V BE1 , making V BE The temperature curve (810) is effectively shifted (rotated) to the adjusted curve, V BE1' - Temperature (830). Differential voltage dV BE' =V BE2 -V BE1' With a more linear temperature dependence, such as Figure 8B dV BE' - Temperature curve (860) shown.

[0065] As a specific example, in Figure 1A In the BJT pair (120), as described above, the differential voltage is given by:

[0066]

[0067] where r is the current density ratio between the two branches. In the case where the current through the two diode-connected transistors is the same, the current density ratio is the inverse of the emitter area ratio, n / m = N. If η varies with temperature rather than being constant, then dV BE Not PTAT. However, according to one aspect of the present invention, V can be amplified differently BE1 and V BE2 To make dV BE Closer to PTAT. For example, V BE1 is amplified by the factor Cs. By properly choosing C s , the differential voltage dV BE =C s V BE1 -V BE More PTAT.

[0068] Specifically, the current I1 through the diode-connected transistor (124) in the first branch (120) is

[0069]

[0070] Among them, I s is the process-dependent saturation current; the current I2 of the transistor (134) connected through the diode in the second branch (130) is

[0071]

[0072] Use C s Amplify V BE1 Equivalent to current I1 Cs :

[0073]

[0074] therefore,

[0075]

[0076] and the differential voltage is

[0077]

[0078] For the case of I1=I2=I,

[0079]

[0080] Where C", dV BE The coefficient (or "slope") in the -T relationship is

[0081]

[0082] Therefore, the coefficients are changed from BE =V BE1 -V BE2 of (i.e., C s =1) is modified to dV BE =C s V BE1 -V BE2 of By properly selecting C s and I (or I1 and I2), factors The introduction of can be used to compensate for the temperature dependence of the ideality factor η, so that the temperature dependence of the coefficient C" as a whole is smaller than η, and dV BE More PTAT, especially within the expected operating temperature range.

[0083] More generally, V BE1 and V BE2 Can be treated differently from each other by other means besides simple amplification. For example, V BE1 and VBE2 amplifier, making C s is a temperature-dependent factor rather than a constant.

[0084] The dV outlined above BE The linearization of the -T relationship can be achieved through various circuits. For example, Figure 9 As shown, discrete timing circuits (such as Figure 3 those shown) can be used to amplify V BE1 and V BE2 In this example, the thermal sensor (900) includes two BJT branches (920, 930). The first branch (920) includes a first current source (922) and a first diode-connected transistor (924); the second branch (930) includes a second current source (932) and a second diode-connected transistor (934). The signal processing circuit in this example includes Figure 3 The switched capacitor amplifiers (310, 340) shown in FIG are a pair of switched capacitor amplifiers (970, 980) of the same type. The amplifiers (970, 980) are connected to receive emitter voltages V from respective branches (920, 930). BE1 and V BE2 As input, amplifiers (970, 980) have different gains S1 and S2, respectively. The outputs of amplifiers (970, 980) provide a differential signal V BE S1 and S2 can be selected to produce a dV with satisfactory PTAT over the expected operating temperature range (e.g., from about -40°C to about 125°C). BE .

[0085] In another embodiment, Figure 10 As shown, the continuous DC type thermal sensor (1000) includes two BJT branches (1020, 1030). The first branch (1020) includes a first current source, which is a MOSFET M1 (1022) in this example, and a first diode-connected transistor (1024); the second branch (1030) includes a second current source, which is a MOSFET M2 (1032) in this example, and a second diode-connected transistor (1034). M1 and M2 form a current mirror with another transistor (in this example, the other transistor is a MOSFET M3 (1040)), and a current identical to the current I1 is provided through M3. The emitter voltage V of the first transistor (1024) is BE1 is applied to the amplifier, which in this example is a voltage divider consisting of resistors R1 (1052) and R2 (1054) connected in series, and has C s=R1 / (R1+R2) gain. The output voltage V1 of the first branch (1020) is taken from the connection between R1 and R2. The output voltage V2 of the second branch (1030) is taken from the emitter of the second transistor (1034), that is, V2=V BE2 The differential output voltage of the thermal sensor (1000) is dV BE =V1-V2.

[0086] In another embodiment, Figure 11 As shown, in addition to using a driver (voltage follower) (1160) to BE1 Provided to the voltage divider formed by the series connected resistors R1 (1052) and R2 (1054), the continuous DC type thermal sensor (1100) and Figure 10 The same as the sensor (1000) in.

[0087] In another embodiment, Figure 12 As shown, the continuous DC type thermal sensor (1200) is similar to Figure 10 and Figure 11 The thermal sensor (1000, 1100) shown in FIG, except that the first branch (1220) includes two sub-branches (1220A, 1220B). Each sub-branch (1220A, 1220B) includes a first current source, which in this example is a MOSFET M1 or M2 (1222A, 1222B), and a first diode-connected transistor (1224A, 1224B); the second branch (1230) includes a second current source, which in this example is a MOSFET M3 (1232), and a second diode-connected transistor (1234). M1, M2, and M3 form a current mirror with another transistor (in this example, the transistor is a MOSFET M4 (1240)), and provide a current identical to the current I1 through M4. In this example, the current density in the first and second sub-branches (1220A, 1220B) is the same but different from the current density in the second branch (1230). The emitter voltage V of the first transistor (1224A) is BE1 is applied to the coefficient (C s ) generator, i.e., an amplifier (e.g., a voltage divider) (1252). The output of the coefficient generator (1252) is determined by V BE Adjustment circuit (1256) fine-tuning, V BE The adjustment circuit (1256) can be an amplifier, such as a variable resistor, which, in combination with the resistors in the voltage divider (1252), can adjust the output voltage of the voltage divider. BEThe output voltage V1 of the regulating circuit (1256) is connected to the emitter of the first diode-connected transistor (1224B). The output voltage V2 of the second branch (1230) is taken from the emitter of the second transistor (1234), that is, V2=V BE2 The differential output voltage of the thermal sensor (1200) is dV BE =V1-V2.

[0088] In another embodiment, Figure 13 As shown, in a thermal sensor (1300) according to one aspect of the present invention, a single diode-connected transistor (1324) is used to alternately generate V under different bias currents. BE , and alternately generate V BE are combined to produce a signal that is essentially PTAT.

[0089] In this embodiment, two current sources (1322, 1332) are connected to the emitter of the diode-connected transistor (1324) via respective switches (e.g., switching transistors) SW1 and SW2 (1326, 1336). The current sources (1322, 1332) provide different current levels to the diode-connected transistor (1324). BE The adjustment circuit (1356) is connected across the diode-connected transistor (1324) via a switch (e.g., a switching transistor) SW3 (1358). Switches SW1, SW2, and SW3 (1326, 1336, 1358) are operated by a control signal (1360) from a processing unit (not shown), such as a microcontroller unit ("MCU"). The emitter voltage of the diode-connected transistor (1324) is input to an analog-to-digital converter ("ADC"); the output of the ADC is connected to a processor, which may be the processing unit or a separate processing unit.

[0090] In operation according to one embodiment, the processing unit outputs a control signal (1360) to alternately turn on SW1 and SW2 to alternately provide two different currents to the diode-connected transistor (1324). When SW1 is turned on or SW2 is turned on, the processing unit outputs a control signal (1360) to turn on SW3. Therefore, according to the control signal (1360), four V BE , V BE Can be used to generate basic PTAT temperature signal: V BE1 is the emitter voltage generated by the first current source (1322), without V BE Adjustment; V BE2 is the emitter voltage generated by the second current source (1332), without V BE Adjustment; V BE3is generated by the first current source (1322) through V BE Adjust the emitter voltage; and V BE4 is generated by the second current source (1332) through V BE Adjusted emitter voltage. Receive V from ADC (1380) BE2 and V BE3 A processor (not shown) can calculate dV BE =V BE3 -V BE2 , through V BE Adjust the appropriate settings of the circuit, dV BE Essentially PTAT. Optionally, the processor can receive V from the ADC (1380). BE1 and V BE4 The digital representation and calculation of dV BE =V BE4 -V BE1 , through V BE Adjust the appropriate settings of the circuit, dV BE Basically it is PTAT. The switch combination obtained and the corresponding dV BE This is summarized in the table below:

[0091]

[0092] Figure 14 Shown in Figure 11 Figure 1 shows the temperature error of the TT process corner of the prototype thermal sensor in the temperature range of -40°C to 125°C, with a single-point calibration at 25°C. It can be seen that the temperature error is within 2°C.

[0093] Although BJTs are used to generate temperature-dependent voltages in many of the thermal sensors described above, other devices with temperature-dependent outputs can be used. For example, any bandgap thermal sensing device can be used. As an example, in some embodiments, diodes are used instead of BJT transistors. In other examples, Figure 1A 、 Figures 3 to 6 and Figures 9 to 13 In all thermal sensors shown in FIG, field effect transistors (FETs) such as MOSFETs are used instead of BJTs. More specifically, FETs operating under subthreshold conditions can be used. In more specific examples, such as Figure 15 As shown, the thermal sensor (1500) is basically the same as Figure 5 The same as the one (500) shown in FIG; except that Figure 5 The diode-connected BJTs (524, 534, 554, 564) in the sensor (500) are replaced by diode-connected MOSFETs (1524, 1534, 1554, 1564). Figure 15 In the sensor (1500), the MOSFETs operate under subthreshold conditions.

[0094] An embodiment of the present invention provides a thermal sensor, comprising: a first temperature-sensitive device, suitable for generating a first temperature-dependent signal; a second temperature-sensitive device, suitable for generating a second temperature-dependent signal; and a signal processing circuit, operably connected to receive the first temperature-dependent signal and the second temperature-dependent signal from the first temperature-sensitive device and the second temperature-sensitive device, and suitable for processing the received signals using processing parameters different from each other to generate a first processing signal and a second processing signal, respectively, and generating an output signal based on the first processing signal and the second processing signal.

[0095] In the above-mentioned thermal sensor, the signal processing circuit is adapted to process the received signal of the first temperature-sensitive device with a first gain factor, and to process the received signal of the second temperature-sensitive device with a second gain factor, the second gain factor being different from the first gain factor, wherein the output signal of the signal processing circuit is a differential signal between the processed signals.

[0096] In the above thermal sensor, each of the first temperature-sensitive device and the second temperature-sensitive device includes two branch circuits, each of the two branch circuits includes a bandgap thermal sensing device and a current source adapted to pass a current through the corresponding bandgap thermal sensing device, and each of the bandgap thermal sensing devices is adapted to generate a signal in response to the current passing through the bandgap thermal sensing device.

[0097] In the above thermal sensor, each of the first temperature-sensitive device and the second temperature-sensitive device includes two branch circuits, each of the two branch circuits includes a bandgap thermal sensing device and a current source adapted to pass a current through the corresponding bandgap thermal sensing device, each of the bandgap thermal sensing devices is adapted to generate a signal in response to the current passing through the bandgap thermal sensing device, wherein the first temperature-dependent signal indicates a difference between the signals generated by the two bandgap thermal sensing devices in the first branch, and the second temperature-dependent signal indicates a difference between the signals generated by the two bandgap thermal sensing devices in the second branch.

[0098] In the above-mentioned thermal sensor, each of the first temperature-sensitive device and the second temperature-sensitive device includes a bandgap thermal sensing device and a current source adapted to pass a current through the corresponding bandgap thermal sensing device, the bandgap thermal sensing device being adapted to generate a signal in response to the current passing through the bandgap thermal sensing device, wherein the signal processing circuit is adapted to process the signal generated by the bandgap thermal sensing device with a first gain factor and to process the signal generated by the bandgap thermal sensing device with a second gain factor, the second gain factor being different from the first gain factor, wherein the output signal of the signal processing circuit is a differential signal between the processed signals.

[0099] In the above thermal sensor, the output signal is proportional to the absolute temperature at the thermal sensor in the temperature range of -50°C to 150°C.

[0100] In the above-mentioned thermal sensor, the output signal is proportional to the absolute temperature in the temperature range of -50°C to 150°C at the thermal sensor, wherein each temperature corresponding to the output signal within the temperature range differs by no more than 5°C from the temperature determined by the proportional relationship between the absolute temperature and the output signal.

[0101] In the above thermal sensor, wherein the output signal is proportional to the absolute temperature in the temperature range of -50°C to 150°C at the thermal sensor, wherein a linear approximation of a first processed signal as a function of the absolute temperature throughout the temperature range has a first offset at 0K, and a linear approximation of a second processed signal as a function of the absolute temperature throughout the temperature range has a second offset at 0K, and the first offset and the second offset are the same.

[0102] In the above thermal sensor, the signal processing circuit includes a discrete timing amplifier.

[0103] In the above thermal sensor, the signal processing circuit includes a continuous DC amplifier.

[0104] In the above-mentioned thermal sensor, each of the first temperature-sensitive device and the second temperature-sensitive device includes two branch circuits, each of the two branch circuits includes a bandgap thermal sensing device and a current source suitable for passing current through the corresponding bandgap thermal sensing device, each of the bandgap thermal sensing devices is suitable for generating a signal in response to the current passing through the bandgap thermal sensing device, wherein each of the bandgap thermal sensing devices includes a bipolar junction transistor, wherein the current source and the bipolar junction transistor in each branch are configured to generate a current density in the bipolar junction transistor, and wherein the current density between the two branches is different.

[0105] In the above-mentioned thermal sensor, each of the first temperature-sensitive device and the second temperature-sensitive device includes two branch circuits, each of the two branch circuits includes a bandgap thermal sensing device and a current source adapted to pass current through the corresponding bandgap thermal sensing device, each of the bandgap thermal sensing devices is adapted to generate a signal in response to the current passing through the bandgap thermal sensing device, wherein each of the bandgap thermal sensing devices includes a field-effect transistor, wherein the current source and the field-effect transistor in each branch are configured to generate a current density in the field-effect transistor, and wherein the current density between the two branches is different.

[0106] In the above-mentioned thermal sensor, wherein the first temperature-sensitive device is set at a certain temperature and includes a bandgap thermal sensing device and a first current source, the first current source is adapted to pass a current of a first value through the bandgap thermal sensing device through a first switching device; the second current source is adapted to pass a current of a second value different from the first value through the bandgap thermal sensing device through a second switching device, the bandgap thermal sensing device is adapted to generate an output signal in response to temperature and current of each of the first value and the second value; wherein the signal processing circuit is operably connected to the bandgap thermal sensing device through a third switching device; wherein the first switching device, the second switching device, and the third switching device are adapted to be cooperatively actuated to alternately connect the first current source to the bandgap thermal sensing device, and connect the signal processing circuit to the bandgap thermal sensing device when the first current source is connected to the bandgap thermal sensing device, and disconnect the signal processing circuit from the bandgap thermal sensing device when the second current source is connected to the bandgap thermal sensing device.

[0107] In the above-mentioned thermal sensor, wherein the first temperature-sensitive device is set at a certain temperature and includes a bandgap thermal sensing device and a first current source, the first current source is adapted to pass a current of a first value through the bandgap thermal sensing device via a first switching device; the second current source is adapted to pass a current of a second value different from the first value through the bandgap thermal sensing device via a second switching device, the bandgap thermal sensing device is adapted to generate an output signal in response to temperature and a current of each of the first value and the second value; wherein the signal processing circuit is operatively connected to the bandgap thermal sensing device via a third switching device; wherein the first switching device, the second switching device and The third switching device is suitable for cooperative actuation to alternately connect the first current source to the bandgap thermal sensing device, and connect the signal processing circuit to the bandgap thermal sensing device when the first current source is connected to the bandgap thermal sensing device, and disconnect the signal processing circuit from the bandgap thermal sensing device when the second current source is connected to the bandgap thermal sensing device, and also includes: a controller, suitable for operating the first switching device, the second switching device and the third switching device, and alternately receiving the output signal in response to the current of the first value and in response to the current of the second value, and generating a signal indicating the temperature from the output signal.

[0108] Another embodiment of the present invention provides a method for temperature measurement, comprising: generating a first current density in a first thermal sensing device set at a temperature T; generating a second current density in a second thermal sensing device set at T, the second current density being different from the first current density; generating a third current density in a third thermal sensing device set at T; generating a fourth current density in a fourth thermal sensing device set at T, the fourth current density being different from the third current density; obtaining a first differential voltage between a first voltage generated by the first thermal sensing device in response to the first current density and T on the one hand and a second voltage generated by the second thermal sensing device in response to the second current density and T on the other hand; obtaining a second differential voltage between a third voltage generated by the third thermal sensing device in response to the third current density and T on the one hand and a fourth voltage generated by the fourth thermal sensing device in response to the fourth current density and T on the other hand; obtaining a third differential voltage dV between the first differential voltage multiplied by a first gain factor and the second differential voltage multiplied by a second gain factor, the second gain factor being different from the first gain factor; and determining T based on the third differential voltage.

[0109] In the above method, determining the temperature T includes: obtaining a value dV0 of the third differential voltage at a single known temperature T0; and determining the temperature T as T=dV·T0 / dV0, where T and T0 are measured in K.

[0110] In the above method, determining the temperature T includes: obtaining the value dV0 of the third differential voltage at a single known temperature T0; and determining the temperature T as T=dV·T0 / dV0, where T and T0 are measured in K, wherein: a linear approximation of the product between the first differential voltage and the first gain factor as a function of absolute temperature within a temperature range has a first offset at 0K; a linear approximation of the product between the second differential voltage and the second gain factor as a function of absolute temperature within a temperature range has a second offset at 0K; and obtaining the third differential voltage includes selecting the first gain factor and the second gain factor so that the first offset and the second offset are the same.

[0111] Yet another embodiment of the present invention provides a method for temperature measurement, comprising: generating a first current density in a first thermal sensing device set at a temperature T to generate a first voltage in response to the first current density and T; generating a second current density in a second thermal sensing device set at T to generate a second voltage in response to the second current density and T, wherein the second current density is different from the first current density; obtaining a differential voltage dV between the first voltage multiplied by a first gain factor and the second voltage multiplied by a second gain factor, wherein the second gain factor is different from the first gain factor; and determining T based on the differential voltage.

[0112] In the above method, wherein determining the temperature T comprises: obtaining a value dV0 of a differential voltage at a single known temperature T0; and determining the temperature T as T=dV·T0 / dV0, wherein T and T0 are measured in K.

[0113] In the above method, determining the temperature T includes: obtaining a value dV0 of a differential voltage at a single known temperature T0; and determining the temperature T as T=dV·T0 / dV0, where T and T0 are measured in K, wherein: the second thermal sensing device is the first thermal sensing device; generating the first current density and the second current density is alternately implemented to alternately generate a first voltage and a second voltage in response to the first current density and the second current density and T, respectively; and obtaining the differential voltage includes multiplying the first voltage by the first gain factor during generating the first current density, and multiplying the second voltage by the second gain factor during generating the second current density.

[0114] The features of several embodiments have been summarized above so that those skilled in the art can better understand aspects of the present invention. Those skilled in the art will appreciate that they can easily use the present invention as a substrate to design or modify other processes and structures for implementing the same purpose and / or achieving the same advantages as the embodiments described herein. Those skilled in the art will also appreciate that this equivalent construction does not deviate from the spirit and scope of the present invention, and that they can make various changes, replacements, and modifications herein without departing from the spirit and scope of the present invention.

Claims

1. A thermal sensor comprising: a first temperature-sensitive device adapted to generate a first temperature-dependent signal, wherein the first temperature-sensitive device comprises two branch circuits, each of the two branch circuits comprising a bandgap thermal sensing device and a current source adapted to pass a current through the corresponding bandgap thermal sensing device, each of the bandgap thermal sensing devices adapted to generate a signal in response to the current passing through the bandgap thermal sensing device; a second temperature-sensitive device adapted to generate a second temperature-dependent signal, wherein the second temperature-sensitive device comprises a single bandgap thermal sensing device and a current source adapted to pass a current through the respective bandgap thermal sensing device, the single bandgap thermal sensing device adapted to generate the signal in response to the current passing through the single bandgap thermal sensing device; a signal processing circuit operatively connected to the two branch circuits of the first temperature sensitive device and adapted to process the received first temperature dependent signal using a processing parameter to generate a first processed signal, wherein the first processed signal is indicative of a difference between signals generated by the bandgap thermal sensing devices in the two branch circuits; Wherein, the thermal sensor generates an output signal based on the first processed signal and the second temperature-dependent signal.

2. The thermal sensor according to claim 1, wherein The bandgap thermal sensing devices in the two branch circuits and the bandgap thermal sensing devices in the second temperature sensitive device include bipolar junction transistors.

3. The thermal sensor according to claim 2, wherein The emitter of the bipolar junction transistor in one of the two branch circuits is connected to a coefficient generator. The thermal sensor according to claim 3 , wherein: The output of the coefficient generator is connected to the signal processing circuit.

5. The thermal sensor according to claim 4, wherein The output of the signal processing circuit is connected to the emitter of the bipolar junction transistor in the other branch of the two branch circuits to generate the first processing signal. The thermal sensor according to claim 1 , wherein: The signal processing circuit includes an amplifier.

7. The thermal sensor according to claim 6, wherein The amplifier is a variable resistor.

8. The thermal sensor according to claim 1, wherein The bandgap thermal sensing devices in the two branch circuits and the single bandgap thermal sensing device in the second temperature sensitive device include field effect transistors.

9. The thermal sensor according to claim 8, wherein The field effect transistor operates under subthreshold conditions.

10. The thermal sensor according to claim 1, wherein The bandgap thermal sensing devices in the two branch circuits have the same current density but different from the current density of the bandgap thermal sensing device in the second temperature sensitive device.

11. The thermal sensor according to claim 1, wherein The output signal is proportional to the absolute temperature at the thermal sensor in the temperature range of -50°C to 150°C.

12. The thermal sensor according to claim 11, wherein Each temperature corresponding to the output signal within the temperature range differs by no more than 5° C. from a temperature determined by a proportional relationship between the absolute temperature and the output signal.

13. The thermal sensor according to claim 11, wherein A linear approximation of the first processed signal as a function of the absolute temperature over the entire temperature range has a first offset at 0 K, and a linear approximation of the second temperature-dependent signal as a function of the absolute temperature over the entire temperature range has a second offset at 0 K, and the first offset and the second offset are the same.

14. The thermal sensor according to claim 1, wherein The signal processing circuit includes a continuous DC type amplifier.

15. The thermal sensor according to claim 1, wherein The current source includes a transistor.

16. A method for temperature measurement, comprising: generating, in a first thermal sensing device set at a temperature T, a first current density through a first bandgap thermal sensing device of a first branch circuit of the first thermal sensing device and a second current density through a second bandgap thermal sensing device of a second branch circuit of the first thermal sensing device to generate a first voltage in response to the first current density, the second current density, and T, wherein each of the first branch circuit and the second branch circuit includes a current source adapted to pass current through the corresponding bandgap thermal sensing device; generating, in a second thermal sensing device disposed at T, a third current density through a second bandgap thermal sensing arrangement of the second thermal sensing device to generate a second voltage in response to the second current density and T; obtaining a differential voltage dV between the first voltage multiplied by the first voltage and the second voltage; and T is determined based on the differential voltage.

17. The method of claim 16, wherein determining the temperature T comprises: obtaining a value dV0 of the differential voltage at a single known temperature T0; and The temperature T is determined as T=dV·T0 / dV0, where T and T0 are measured in K.

18. The method according to claim 17, wherein: The first bandgap thermal sensing device and the second bandgap thermal sensing device are diode-connected transistors.

19. The method according to claim 16, wherein The first voltage is generated by a signal processing circuit operatively connected to the first branch circuit and the second branch circuit.

20. The method according to claim 16, wherein The first current density and the second current density are the same but different from the third current density.

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