Thermal sensor and method of temperature measurement

Abstract

Embodiments of the invention provide a thermal sensor comprising: a single first temperature sensitive device comprising a single bandgap thermal sensing device; a first current source connected to the first temperature sensitive device by a first switch, the first current source being adapted to pass a first value of current through the bandgap thermal sensing device by the first switching device; a second current source connected to the first temperature sensitive device by a second switch, the bandgap thermal sensing device being adapted to generate a temperature dependent signal in response to temperature and current at each of the first value and the second value; a signal processing circuit operably connected to the bandgap thermal sensing device by a third switching device and, when connected to the bandgap thermal sensing device, processing a received temperature dependent signal to generate a processed signal; wherein the first, second and third switching devices are adapted to be actuated in concert to alternately connect the first current source and the second current source to the bandgap thermal sensing device. Embodiments of the invention also relate to methods of temperature measurement.

Description

[0001] Divisional application

[0002] This application is a divisional application of patent application No. 201910931842.1, filed on September 29, 2019, entitled "Thermal Sensor and Method for Temperature Measurement". Technical Field

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

[0004] This invention generally relates to thermal sensors. More specifically, this invention relates to reducing the temperature error of thermal sensors.

[0005] Thermal sensors have a wide range of applications. For many applications, the accuracy of thermal sensors is important, even crucial. When a thermal sensor is calibrated only at one or a limited number of temperatures, it can be difficult to ensure its accuracy throughout its intended use due to deviations in sensor characteristics from ideal properties. Efforts are underway to improve the accuracy of thermal sensors. Summary of the Invention

[0006] Embodiments of the present invention provide a thermal sensor, comprising: a first temperature-sensitive device adapted to generate a first temperature-dependent signal; a second temperature-sensitive device adapted to generate a second temperature-dependent signal; and a signal processing circuit operatively 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 adapted to process the received signals using different processing parameters to generate a first processed signal and a second processed signal, respectively, and to generate an output signal based on the first processed signal and the second processed 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 disposed at a temperature T; generating a second current density in a second thermal sensing device disposed at T, the second current density being different from the first current density; generating a third current density in a third thermal sensing device disposed at T; generating a fourth current density in a fourth thermal sensing device disposed 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 and a second voltage generated by the second thermal sensing device in response to the second current density and T; 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 and a fourth voltage generated by the fourth thermal sensing device in response to the fourth current density and T; 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] Another embodiment of the present invention provides a method for temperature measurement, comprising: generating a first current density in a first thermal sensing device disposed 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 disposed 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. Attached Figure Description

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

[0010] Figure 1A A component of a thermal sensor according to one aspect of the present invention is illustrated schematically.

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

[0012] Figure 2AThis is a diagram illustrating the voltage-temperature relationship within the operating temperature range of a component thermal sensor, approximating one aspect of the invention.

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

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

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

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

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

[0018] Figure 7 It shows Figure 6 Temperature performance data of the prototype thermal sensor of the type shown 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 invention is shown, as well as a partial slope adjustment of the voltage-temperature relationship of one of the transistors.

[0020] Figure 8B It shows having Figure 8A The differential voltage-temperature relationship of the thermal sensor is shown in the voltage-temperature relationship diagram.

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

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

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

[0024] Figure 12 A schematic illustration of a V according to one aspect of the invention is shown. beA continuous DC thermal sensor circuit with partial slope adjustment was replicated.

[0025] Figure 13 A schematic illustration shows a switching single-transistor branch thermal sensor circuit with partial slope adjustment controlled by a digital control unit (e.g., a microcontroller (“MCU”)) according to one aspect of the invention.

[0026] Figure 14 It shows Figure 11 Temperature performance data at the process corner of the prototype thermal sensor of the type shown.

[0027] Figure 15 A continuous DC thermal sensor circuit with differential feedback according to one aspect of the invention is schematically shown, similar to... Figure 5 The circuit shown is an example of a circuit where the bipolar junction transistor is replaced by a field-effect transistor.

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

[0029] The following disclosure provides numerous different embodiments or examples for implementing various features of the invention. Specific embodiments or examples of components and arrangements are described below to simplify the invention. These are merely examples and not intended to be limiting. For example, in the following description, forming a first component on or over a second component can include embodiments where the first and second components are in direct contact, and can also include embodiments where an additional component can be formed between the first and second components, such that the first and second components are not in direct contact. As used herein, forming a first component on a second component means forming a first component in direct contact with the second component. Furthermore, reference numerals and / or letters may be repeated in various examples. This repetition is for 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 circuit to ensure its proper operation. Examples of thermal sensors include sensors employing bipolar junction transistors (“BJTs”), where the voltage between the terminal pairs (such as base-emitter voltage or VT) is measured. BE The temperature sensor exhibits a certain temperature dependence, which possesses characteristics such as exponential dependence under ideal (theoretical) conditions. Deviations from these ideal characteristics can lead to temperature measurement errors. Some embodiments disclosed herein demonstrate lower temperature errors than conventional 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. Each BJT generates V0. BE As a result, obtain the difference V in each pair. BE (dV BE or ΔV BE ) or two V BE The difference between them, and the dV in the two pairs BE The difference between them is used as the output signal. The dV values ​​from these pairs... BE It can be amplified differently, making dV BE The parameters have essentially the same offset value (S1), such as the offset voltage at a reference temperature (e.g., 0 K), where the offset voltage can be defined as dV at the calibration point (e.g., 25 °C). BE Tangent to the temperature curve (or dV within the operating temperature range) BE The offset voltage at a reference temperature (some other linear approximations of the temperature profile). Other forms of approximations 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 can be used, but V can be amplified differently. BE This makes the amplified V BE The temperature profiles closely match within the expected operating temperature range.

[0033] refer to Figure 1A Two BJT pairs (110, 140) are configured to generate dV. BE (respectively dV) BE1 and dV BE2 These will be combined to provide a voltage signal that is closer to having a more ideal temperature dependence than either of the BJT pairs (110, 140). This more ideal temperature dependence can be achieved, for example, through linear dependence, where the voltage is substantially proportional to the absolute temperature (“PTAT”), making single-point temperature calibration (e.g., at 25°C) sufficiently reliable for temperature sensing across the entire expected temperature range for the operation of the electronics (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).

[0034] Figure 1AEach BJT pair (110, 140) in the example shown comprises two branches connected in parallel (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). The base and collector of 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 with its own 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. Therefore, different current densities can be generated by currents of different amplitudes from current sources (122, 132, 152, 162), where the emitter-base junction cross-sectional area is the same in the diode-connected transistors (124, 134, 154, 164). Different current densities can also be generated by currents of the same amplitude from current sources (122, 132, 152, 162), but with different emitter regions n, m, p, and q for each diode-connected transistor (124, 134, 154, 164). In another alternative, different current densities can be generated by currents of different amplitudes from current sources (122, 132, 152, 162), wherein the emitter-base junctions of diode-connected transistors (124, 134, 154, 164) have different cross-sectional areas.

[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 of the two diode-connected transistors. Therefore, 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 This makes it temperature dependent. 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. When the currents in the two branches of each BJT pair are equal, 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 representing dV as a function of temperature is a straight line passing through the origin, that is, at T = 0 K. BE = 0V. Therefore, for the BJT pair (110, 140), the ideal dV is 0V. BE1 -T and dV BE2 The -T curves will be respectively Figure 1B The straight line (170, 180) in the figure. However, in practical thermal sensors, the ideality factor η typically does not change with temperature. Therefore, dV BE -T relationships are usually not linear, as shown by curves (172, 182) for BJT pairs (110, 140).

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

[0042] In practical applications, the calibration accuracy of temperature sensors only relates to the expected operating temperature range, such as approximately 40°C to approximately 125°C. According to certain aspects of the invention, differential base-emitter voltages from two BJT pairs (110, 140) can be suitably combined to obtain a signal that is substantially PTAT, at least within the expected operating temperature range, such that single-point calibration is sufficient for the intended operation of the electronic device. For example, in Figure 2A In the middle, dV BE2 The -T curve (182) can be adequately approximated by a straight line (220) over a temperature range of approximately 40°C to approximately 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) could be dV at a calibration temperature (e.g., 25°C). BE2 -T curve tangent; in another example, line (220) is the 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) may be the least squares fit of the curve within the expected temperature range.

[0043] Similarly, such as dV BE1 As shown in the -T curve (172), it can be compared with dV BE2 The -T curve (182) is approximated by a straight line (not shown in the figure) over the same temperature range. In this case, dV BE2 The line (220) of the -T curve (182) intersects at point S1 on the y-axis (i.e., 0K); in this case, dV BE1 The line of the -T curve (172) intersects at point S2 on the y-axis. According to an aspect of the invention, dV BE1 It can be amplified by a factor M (which can be larger, equal to, or less than 1) so that M·S2 = S1. For example... Figure 2B As shown, the line (280)M×dV of the approximately magnified differential voltage curve (272) BE1 With dV BE2 -T curve (182) intersects at point S1. Differential voltage dV BE12 In this form, dVBE12=M·dVBE1-dVBE2≈C′T+M·S2-C″T-S1=(C′-C″)T,

[0044] Where C' and C” are constants. Therefore, the combined differential voltage is essentially PTAT, and the thermal sensor that generates this differential voltage is suitable for single-point calibration. That is, the differential voltage value dV0 and dV at a single known temperature T0 (e.g., 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.

[0045] dVBE12=M·dVBE1-N·dVBE2,

[0046] It is basically a PTAT signal.

[0047] Therefore, in order to obtain a substantially PTAT signal in temperature measurement, according to some embodiments, the following steps can be taken: generating a first current density (1610) in a first thermal sensing device located at temperature T; generating a second current density (1620) in a second thermal sensing device located at T, the second current density being different from the first current density; generating a third current density (1630) in a third thermal sensing device located at T; generating a fourth current density (1640) in a fourth thermal sensing device located at T, the fourth current density being different from the third current density; and the first thermal sensing device responding to the first current density and T... A first differential voltage is obtained between the first voltage generated and the second voltage generated by the second thermal sensing device in response to the second current density and T (1650); a second differential voltage is obtained between the third voltage generated by the third thermal sensing device in response to the third current density and T and the fourth voltage generated by the fourth thermal sensing device in response to the fourth current density and T (1660); a third differential voltage dV is obtained between the first differential voltage multiplied by the first gain factor and the second differential voltage multiplied by the second gain factor, the second gain factor being different from the first gain factor (1670); and T is determined based on the third differential voltage (1680).

[0048] refer to Figure 3 According to one aspect of the invention, a thermal sensor circuit (300) implements the above-described scheme for obtaining a basic PTAT thermal sensor. In this example, the circuit (300) is a discrete timing circuit. It includes the aforementioned BJT pair (110, 140) and a signal processing circuit, which in this example 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), which can be any suitable switching device, including a switching transistor. Similarly, the switched-capacitor amplifier (340) includes an operational amplifier (342), an input capacitor (344), a feedback capacitor (346), and switches (348, 350, 352), which can be any suitable switching device, including a switching transistor. The switch inputs of the amplifier (310) are connected to the respective emitters of diode-connected transistors (124, 134) to receive the differential signal dV. BE1 dV BE1 V is the voltage V at the emitter of the diode-connected transistor (124).BE1a The voltage V at the emitter of the transistor (134) connected to the diode BE1b The difference between them. Similarly, the switching inputs of the amplifier (340) are connected to the corresponding emitters of diode-connected transistors (154, 164) to receive the differential signal dV. BE2 The differential signal dV BE2 It is the voltage V at the emitter of the diode-connected transistor (154). BE2a The voltage V at the emitter of the transistor (164) connected to the diode. BE2b The difference between them.

[0049] In one example, amplifiers (310, 340) have gains M and N, respectively, where M·S2-NS1=0, and S1 and S2 are approximate dV values ​​over the expected operating temperature range (e.g., from about 40°C to about 125°C). BE2 -T curve (182) and dV BE1 -T curve (172) line y-crosses. As mentioned above, the differential output signal dV BE12 It is basically proportional to the absolute temperature within the expected operating temperature range. Therefore, the thermal sensor (300) is susceptible to single-point calibration.

[0050] As used in this invention, "gain" or "amplification" means a factor by which the signal input to the circuit ("amplifier") is multiplied to generate the circuit's output; the factor is not limited to a number greater than 1.

[0051] Other discrete timing circuits, such as switched capacitor sample / hold circuits, can also be used.

[0052] The signal processing circuit used to obtain different gains for the two BJT pairs can be of any type suitable for this purpose. For example, a continuous DC circuit can also be used. Figure 4 In this case, a continuous DC amplifier (400) can be used instead. Figure 3The switched-capacitor amplifiers (310, 340) 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 OR operational amplifiers (452, 454), an input resistor (456) associated with the operational amplifier (452), and a feedback resistor (458), as well as an input resistor (460) associated with the operational amplifier (454) and a feedback resistor (462). The summing amplifiers (410, 430) receive two pairs of inputs: V0 of the amplifier (410). BE1a and V BE2b and the V of the amplifier (430) BE2a and V BE1b The outputs of the summing amplifiers (410, 430) are the inputs 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 A linear combination. By appropriately selecting the resistor value, ΔV can be set as dV. BE1 and dV BE2 A linear combination of. For example, for Figure 4 For the symbolized resistance values ​​in the diagram, for R1 = R2 = R3 = R4, ΔV = M·dV BE1 -dV BE2 , where M is a value that makes ΔV substantially proportional to the absolute temperature (e.g., M·S2-S1=0).

[0053] refer to Figure 5According to another aspect of the invention, the thermal sensor circuit (500) includes two branches of a BJT pair (510, 540). The first BJT pair (510) includes a pair of diode-connected transistors (524, 534) and current-biased transistors M1 (522), M2 (526), ​​M3 (532), and M4 (536), wherein the reference numerals “M1”, “M2”, “M3”, and “M4” also indicate the dimensions of the respective transistors (522, 526, 532, 536), such as the channel width. Similarly, the second BJT pair (540) includes a pair of diode-connected transistors (554, 564) and current-biased transistors M5 (552), M6 (556), M7 (562), and M8 (566), where the designations “M5”, “M6”, “M7”, and “M8” also indicate the dimensions of the individual transistors (552, 556, 562, 566), such as the channel width. The transistors M1-M8 in this example are field-effect transistors (FETs), such as metal-oxide-semiconductor field-effect transistors (MOSFETs), but can 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 drain 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 drain of transistors M6 (556) and M1 (522). The emitter of transistor (534) connected to the second diode in the first branch (510) is connected to the drain of transistors M3 (532) and M8 (566) via resistor R1 (538). The emitter of transistor (564) connected to the second diode in the second branch (540) is connected to the drain of transistors M7 (562) and M4 (536) via resistor R2 (568).

[0054] Each branch (510, 540) is associated with a corresponding amplifier (570, 580). The input of the first amplifier (570) is the differential voltage dV between the emitters of the diode-connected transistors (524, 534) via resistor R1 (538). BE1 The input of the second amplifier (580) is the differential voltage dV between the emitters of the diode-connected transistors (554, 564) via resistor R2 (568). BE2 The output of the first amplifier (570) is connected to the control electrode (gate 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 electrode (gate in this example) of transistors M5 (552), M6 (556), M7 (562) and M8 (566).

[0055] The first output V of the thermal sensor (500) out1 Provided at the junction between the first output resistor R4 (598) and the drain of the first output transistor M10 (596); the second output V of the thermal sensor (500) out2 A junction is provided 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 Furthermore, transistor M1 generates a mirror current I2. Similarly, transistor M9 and resistor R3 form a second current mirror with transistor M8, generating a voltage output V from resistor R3. out2 And a mirror current I1 is generated through transistor M8.

[0056] In this example, the output is V. out1 and V out2 Each is a dV BE1 and dV BE2 The function, each dV BE1 and dV BE2 It is a function of the current density ratio in the BJT with respect to (510, 540). (And...) Figure 3 The configuration shown is similar, and the current density ratio in each BJT pair can be set using the same BJT size (n = m; p = q), but through transistors M2 and M3 (for BJT pair (510)) (I M2 :I M3 ), or M6 and M7 (for BJT pairs (540)(I M6 :I M7 The ratio between the currents of the transistors M2 and M3 is inconsistent. Optionally, the current density ratio in each BJT pair can be determined by transistors M2 and M3 (I M2 :I M3 =1) or M6 and M7 (I M6 :I M7 =1) can be used to set the same current but with different BJT sizes. Alternatively, a combination of the two configurations above can be used (i.e., different BJT sizes and transistor currents).

[0057] Current ratio I M2 :I M3 and IM6 :I M7 Then they are dV BE1 / R1 and dV BE2 The current ratio is a function of / R2. The current ratio is also 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 the transistors is the aspect ratio (width:length) of the transistor channels. 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 It is k1(m1dV) BE1 -dV BE2 ), where k1 and m1 are functions of R1, R2, m, k, and R4; similarly, the output V out2 It is k2(m2dV) BE2 -dV BE1 ), where k2 and m2 are functions of R1, R2, m, k, and R3. Therefore, by appropriately selecting the resistance values ​​R1, R2, R3, and R4, and the ratios m and k, dV can be set. BE2 and / or dV BE1 The voltage offset is used to generate a PTAT voltage suitable for single-point calibration.

[0058] refer to Figure 6According to another aspect of the invention, the thermal sensor circuit (600) includes two branches of a BJT pair (610, 640). The first BJT pair (610) includes a pair of diode-connected transistors (624, 634) and current-biased transistors M1 (522), M2 (626), and M3 (632), wherein the reference numerals "M1", "M2", and "M3" also indicate the dimensions of each transistor (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-biased transistors M4 (656), M5 (662), and M6 (666), wherein the reference numerals "M4", "M5", and "M6" also indicate the dimensions of each transistor (656, 662, 666), such as the channel width. In this example, transistors M1-M6 are field-effect transistors (FETs), such as metal-oxide-semiconductor field-effect transistors (MOSFETs), but can be any suitable type of transistor. The emitter of transistor (624), connected to the first diode in the first branch (610), is directly connected to the drain of transistors M2 (626) and M6 (666); the emitter of transistor (654), connected to the first diode in the second branch (640), is directly connected to the drain of transistor M4 (656). The emitter of transistor (634), connected to the second diode in the first branch (610), is connected to the drain of transistor M3 (632) via resistor R1 (638); the emitter of transistor (664), connected to the second diode in the second branch (640), is connected to the drain of transistors M5 (662) and M1 (622) via resistor R2 (668).

[0059] Each branch (510, 540) is associated with a corresponding amplifier (670, 680). The input of the first amplifier (670) is the differential voltage dV between the emitters of the diode-connected transistors (624, 634) via resistor R1 (638). BE1 The input of the second amplifier (680) is the differential voltage dV between the emitters of the diode-connected transistors (654, ​​664) via 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).

[0060] The first output V of the thermal sensor (600) out1Provided at the junction between the first output resistor R4 (698) and the drain of the first output transistor M7 (696); the second output V of the thermal sensor (600) is provided at the junction between the first output resistor R4 (698) and the drain of the first output transistor M7 (696). out2 A junction is provided 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 a mirror current I2 is generated 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 a mirror current I1 is generated through transistor M6.

[0061] In this example, the output is V. out1 and V out2 Each is a dV BE1 and dV BE2 The function, each dV BE1 and dV BE2 It is a function of the current density ratio in the BJT with respect to (610, 640). (And...) Figure 3 and Figure 5 The configuration shown is similar, and the current density ratio in each BJT pair can be determined by the BJT size (n / m; p / q) and by transistors M1, M2, and M3 (for BJT pair (610)) (I M1 :I M2 :I M3 ), or M4, M5 and M6 (for BJT pairs (640))(I M4 :I M5 :I M6 The ratio is set by the combination of the ratios between the currents. The current ratios are then respectively dV. BE1 / R1 and dV BE2 The current ratio is a function of / R2. It is also a function of the W / L ratio among transistors M1, M2, and M3, and among M4, M5, and M6. Figure 5 The configuration shown is similar, in Figure 6 In the configuration, the output V out1 For 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 It 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 resistance values ​​R1, R2, R3, and R4, and the W / L ratios, dV can be set. BE2 and / or dV BE1 The voltage offset is used to generate a PTAT voltage suitable for single-point calibration. For example, Figure 7 It shows Figure 6 The temperature error at several process corners (TT, FF, and SS) of the thermal sensor is shown as a function of temperature. Single-point calibration was performed at 25°C. The temperature error over the temperature range of -25°C to 110°C is within approximately 3°C. That is, in dV BE12 -T diagram passes through (T=0K, dV) BE12 =0V) and (T = 273K + 25K, dV BE12 The temperature determined by the straight line (PTAT) 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 = 0 K, dV)... BE12 =0V) straight line (PTAT) and at dV BE12 Calibration points in the -T curve (e.g., T = 273K + 25K, dV) BE12 If the difference between the temperature determined at 25°C and the actual temperature does not exceed an acceptable amount (e.g., 3, 2, or 1°C) for the correct operation of the device (e.g., integrated circuit) within the expected temperature range, then the output of the thermal sensor is essentially PTAT.

[0062] 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 signal (temperature) that is more linear than that from a single transistor. For example, in one aspect of the invention, V relative to transistors (124, 134) BE The base-emitter voltage (V) in a single BJT pair (such as BJT pair (110)) can be appropriately combined. BE This is to generate a signal that is more linear with absolute temperature.

[0063] like Figure 8A As shown, each transistor in a BJT pair, such as Figure 1A The BJT pair (110) shown generates a temperature-dependent V BE Therefore, for example, the voltage V at the emitter of the diode-connected transistor (124) BE1 With VBE Temperature curve (810), and voltage V at the emitter of diode-connected transistor (134). BE2 With V BE Temperature profile (820). (e.g.) Figure 8B As shown, the differential voltage dV BE (840) can 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 invention, V can be adjusted (e.g., amplified) relative to each other. BE1 and V BE3 Any of the above to achieve a more linear dV BE For example, in one embodiment, relative to V BE2 Adjust (e.g., by amplifying) V BE1 This makes V BE The temperature curve (810) is effectively moved (rotated) to the adjusted curve, V BE1' -Temperature (830). Differential voltage dV BE' =V BE2 -V BE1' It has a more linear temperature dependence, such as Figure 8B dV in BE' -Temperature curve (860) is shown.

[0064] As a specific example, in Figure 1A In the BJT pair (120), as described above, the differential voltage is given by the following equation:

[0065]

[0066] Where r is the current density ratio between the two branches. When the current through the two diodes connected in a transistor is the same, the current density ratio is the reciprocal of the emitter area ratio, n / m = N. If η varies with temperature instead of being constant, then dV BE Not PTAT. However, according to one aspect of the invention, V can be amplified differently. BE1 and V BE2 Make dV BE Closer to PTAT. For example, V BE1 Amplified by the factor Cs. This can be achieved by appropriately selecting C. s This can make the differential voltage dV BE =C s V BE1 -V BE More PTAT.

[0067] Specifically, the current I1 of the transistor (124) connected through the diode in the first branch (120) is

[0068]

[0069] Among them, I s It is a process-dependent saturation current; the current I2 of the transistor (134) connected through the diode in the second branch (130) is

[0070]

[0071] Use C s Enlarge V BE1 Equivalent to having current I1 Cs :

[0072]

[0073] therefore,

[0074]

[0075] And the differential voltage is

[0076]

[0077] For the case where I1 = I2 = I...

[0078]

[0079] Where C”, dV BE The coefficient (or "slope") in the -T relationship is

[0080]

[0081] Therefore, the coefficients from dV BE =V BE1 -V BE2 of (that is, C) s =1) Modified to be for dV BE =C s V BE1 -V BE2 of By appropriately selecting C s And I (or I1 and I2), factor The introduction of can be used to compensate for the temperature dependence of the ideal factor η, making the temperature dependence of the coefficient C” as a whole less than η, and dV BE More PTAT, especially within the expected operating temperature range.

[0082] More generally, V BE1 and V BE2 They can be distinguished from each other in ways other than simple amplification. For example, V can be configured. BE1 and VBE2 The amplifier makes C s It is a temperature-dependent factor, not a constant.

[0083] The dV described above BE Linearization of the -T relationship can be achieved through various circuits. For example, such as... Figure 9 As shown, discrete timing circuits (such as...) Figure 3 Those shown can be used to amplify V differently. 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 transistor (924) connected to a first diode; the second branch (930) includes a second current source (932) and a transistor (934) connected to a second diode. The signal processing circuit in this example includes... Figure 3 The switched-capacitor amplifiers (310, 340) shown are a pair of switched-capacitor amplifiers (970, 980) of the same type. Amplifiers (970, 980) are connected to receive emitter voltage V from their respective branches (920, 930). BE1 and V BE2 As inputs, 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 satisfactory dV of PTAT within the expected operating temperature range (e.g., from about -40°C to about 125°C). BE .

[0084] In another embodiment, such as Figure 10 As shown, the continuous DC thermal sensor (1000) includes two BJT branches (1020, 1030). The first branch (1020) includes a first current source, in this example a MOSFET M1 (1022), and a first diode-connected transistor (1024); the second branch (1030) includes a second current source, in this example a MOSFET M2 (1032), 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 the same current as current I1 is supplied through M3. The emitter voltage V of the first transistor (1024) is... BE1 The voltage 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=Gain of R1 / (R1+R2). 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), i.e., V2 = V BE2 The differential output voltage of the thermal sensor (1000) is dV. BE =V1-V2.

[0085] In another embodiment, such as Figure 11 As shown, in addition to using a driver (voltage follower) (1160) to convert V BE1 In addition to the voltage divider formed by the series-connected resistors R1 (1052) and R2 (1054), the continuous DC thermal sensor (1100) and Figure 10 The sensor (1000) in it is the same.

[0086] In another embodiment, such as Figure 12 As shown, the continuous DC thermal sensor (1200) is similar to Figure 10 and Figure 11 The thermal sensors (1000, 1100) shown include two sub-branches (1220A, 1220B) in addition to the first branch (1220). Each sub-branch (1220A, 1220B) includes a first current source, in this example a MOSFET M1 or M2 (1222A, 1222B), and a first diode-connected transistor (1224A, 1224B); the second branch (1230) includes a second current source, in this example 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 MOSFET M4 (1240)) and provide the same current as 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 Applied to coefficient (C) s The coefficient generator (1252) is an amplifier (e.g., a voltage divider). The output of the coefficient generator (1252) is determined by V... BE Adjusting circuit (1256) for 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 adjustment 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), i.e., V2 = V BE2 The differential output voltage of the thermal sensor (1200) is dV. BE =V1-V2.

[0087] In another embodiment, such as Figure 13 As shown, in a thermal sensor (1300) according to one aspect of the invention, a single diode-connected transistor (1324) is used to alternately generate V under different bias currents. BE And the alternately generated V BE They are combined to produce a signal that is essentially PTAT.

[0088] In this embodiment, two current sources (1322, 1332) are connected to the emitter of a diode-connected transistor (1324) via corresponding 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.

[0089] In one embodiment, the processing unit outputs a control signal (1360) to alternately turn on SW1 and SW2, thereby alternately supplying two different currents to the diode-connected transistor (1324). When SW1 or SW2 is on, the processing unit outputs the control signal (1360) to turn on SW3. Therefore, according to the control signal (1360), four VC signals can be generated. BE V BE It can be used to generate a basic PTAT temperature signal: V BE1 The emitter voltage is generated by the first current source (1322), and there is no V. BE Adjustment; V BE2 The emitter voltage is generated by the second current source (1332), and there is no V. BE Adjustment; V BE3It is generated by the first current source (1322) via V BE Adjusted emitter voltage; and V BE4 It is generated by the second current source (1332) via V BE Adjusted emitter voltage. Receive V from ADC (1380). BE2 and V BE3 A digitally represented processor (not shown) can calculate dV. BE =V BE3 -V BE2 via V BE Adjust the appropriate circuit settings, dV BE Essentially, it's PTAT. Optionally, the processor can receive V from the ADC (1380). BE1 and V BE4 The numerical representation of dV is used to calculate dV. BE =V BE4 -V BE1 via V BE Adjust the appropriate circuit settings, dV BE Basically, it's PTAT. The obtained switch combinations and corresponding dV BE The summary is shown in the table below:

[0090]

[0091] Figure 14 It shows in Figure 11 The prototype thermal sensor, manufactured using the TT process, exhibits a temperature error at the corner within a range of -40℃ to 125℃, with single-point calibration performed at 25℃. It can be seen that the temperature error is within 2℃.

[0092] While BJTs are used to generate temperature-dependent voltages in many of the aforementioned thermal sensors, 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, diodes can be used instead of BJT transistors. Figure 1A , Figures 3 to 6 and Figures 9 to 13 All the thermal sensors shown use field-effect transistors (FETs) such as MOSFETs instead of BJTs. More specifically, FETs that operate under subthreshold conditions can be used. In a more specific example, such as Figure 15 As shown, the thermal sensor (1500) is basically the same as Figure 5 The one shown (500) is the same; the difference is that, Figure 5 In the sensor (500), the diode-connected BJTs (524, 534, 554, 564) are replaced by diode-connected MOSFETs (1524, 1534, 1554, 1564). Figure 15 In the sensor (1500), these MOSFETs operate under subthreshold conditions.

[0093] Embodiments of the present invention provide a thermal sensor, comprising: a first temperature-sensitive device adapted to generate a first temperature-dependent signal; a second temperature-sensitive device adapted to generate a second temperature-dependent signal; and a signal processing circuit operatively 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 adapted to process the received signals using different processing parameters to generate a first processed signal and a second processed signal, respectively, and to generate an output signal based on the first processed signal and the second processed signal.

[0094] In the aforementioned thermal sensor, the signal processing circuit is adapted to process the received signal from the first temperature-sensitive device with a first gain factor and to process the received signal from the second temperature-sensitive device with a second gain factor, wherein the second gain factor is different from the first gain factor, and the output signal of the signal processing circuit is a differential signal between the processed signals.

[0095] 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 including a bandgap thermal sensing device and a current source adapted to pass current through the respective bandgap thermal sensing device, each of the bandgap thermal sensing devices being adapted to generate a signal in response to the current passing through the bandgap thermal sensing device.

[0096] In the aforementioned 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 including a bandgap thermal sensing device and a current source adapted to pass current through the respective bandgap thermal sensing device, each of the bandgap thermal sensing devices being adapted to generate a signal in response to the current passing through the bandgap thermal sensing device, wherein the first temperature-dependent signal indicates the difference between the signals generated by the two bandgap thermal sensing devices in the first branch, and the second temperature-dependent signal indicates the difference between the signals generated by the two bandgap thermal sensing devices in the second branch.

[0097] In the aforementioned 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 current through the respective bandgap thermal sensing device. The bandgap thermal sensing device is adapted to generate a signal in response to the current passing through the bandgap thermal sensing device. The signal processing circuit is adapted to process the signal generated by the bandgap thermal sensing device with a first gain factor and with a second gain factor, the second gain factor being different from the first gain factor. The output signal of the signal processing circuit is a differential signal between the processed signals.

[0098] In the aforementioned thermal sensor, the output signal is proportional to the absolute temperature at the thermal sensor, which ranges from -50°C to 150°C.

[0099] In the aforementioned thermal sensor, the output signal is proportional to the absolute temperature at the thermal sensor, which ranges from -50°C to 150°C, wherein each temperature corresponding to the output signal within the temperature range differs from the temperature determined by the proportional relationship between the absolute temperature and the output signal by no more than 5°C.

[0100] In the aforementioned thermal sensor, the output signal is proportional to the absolute temperature at the thermal sensor, which ranges from -50°C to 150°C. A linear approximation of a first processed signal, which is a function of the absolute temperature over the entire temperature range, has a first offset at 0K, and a linear approximation of a second processed signal, which is a function of the absolute temperature over the entire temperature range, has a second offset at 0K. The first offset and the second offset are the same.

[0101] In the aforementioned thermal sensor, the signal processing circuit includes a discrete timing amplifier.

[0102] In the aforementioned thermal sensor, the signal processing circuit includes a continuous DC amplifier.

[0103] In the aforementioned 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 including a bandgap thermal sensing device and a current source adapted to allow current to pass through the respective bandgap thermal sensing device, each of the bandgap thermal sensing devices being 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 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 densities between the two branches are different.

[0104] In the aforementioned 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 including a bandgap thermal sensing device and a current source adapted to pass current through the respective bandgap thermal sensing device, each of the bandgap thermal sensing devices being adapted to generate a signal in response to the current passing through the bandgap thermal sensing device, each of the bandgap thermal sensing devices including 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 densities between the two branches are different.

[0105] In the aforementioned thermal sensor, the first temperature-sensitive device is disposed at a certain temperature and includes a bandgap thermal sensing device and a first current source. The first current source is adapted to allow a first value of current to pass through the bandgap thermal sensing device via a first switching device. A second current source is adapted to allow a second value of current, different from the first value, to pass 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 the temperature and the current of each of the first and second values. The signal processing circuit is operatively connected to the bandgap thermal sensing device via a third switching device. The first, second, and third switching devices are adapted to be cooperatively actuated to alternately connect the first current source to the bandgap thermal sensing device, and to 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 to disconnect the signal processing circuit from the bandgap thermal sensing device when the second current source is connected to the bandgap thermal sensing device.

[0106] In the aforementioned thermal sensor, the first temperature-sensitive device is positioned at a certain temperature and includes a bandgap thermal sensing device and a first current source. The first current source is adapted to allow a first value of current to pass through the bandgap thermal sensing device via a first switching device. A second current source is adapted to allow a second value of current, different from the first value, to pass 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 the temperature and the current of each of the first and second values. The signal processing circuit is operably connected to the bandgap thermal sensing device via a third switching device. The first switching device, the second switching device, and... The third switching device is adapted to be cooperatively actuated to alternately connect the first current source to the bandgap thermal sensing device, and to 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 to disconnect the signal processing circuit from the bandgap thermal sensing device when the second current source is connected to the bandgap thermal sensing device. The device further includes a controller adapted to operate the first switching device, the second switching device, and the third switching device, and to alternately receive the output signal in response to a current of the first value and a current of the second value, and to generate a signal indicating the temperature from the output signal.

[0107] Another embodiment of the present invention provides a method for temperature measurement, comprising: generating a first current density in a first thermal sensing device disposed at a temperature T; generating a second current density in a second thermal sensing device disposed at T, the second current density being different from the first current density; generating a third current density in a third thermal sensing device disposed at T; generating a fourth current density in a fourth thermal sensing device disposed 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 and a second voltage generated by the second thermal sensing device in response to the second current density and T; 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 and a fourth voltage generated by the fourth thermal sensing device in response to the fourth current density and T; 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.

[0108] 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.

[0109] 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 such that the first offset and the second offset are the same.

[0110] Another embodiment of the present invention provides a method for temperature measurement, comprising: generating a first current density in a first thermal sensing device disposed 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 disposed 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.

[0111] In the above method, determining the temperature T includes: obtaining the value of the differential voltage dV0 at a single known temperature T0; and determining the temperature T as T = dV·T0 / dV0, where T and T0 are measured in K.

[0112] In the above method, determining the temperature T includes: obtaining the value of the differential voltage dV0 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; alternately generating the first current density and the second current density to generate a first voltage and a second voltage respectively in response to the first current density and the second current density alternating with T; and obtaining the differential voltage includes multiplying the first voltage by the first gain factor during the generation of the first current density, and multiplying the second voltage by the second gain factor during the generation of the second current density.

[0113] The foregoing outlines features of several embodiments to enable those skilled in the art to better understand aspects of the invention. Those skilled in the art should understand that they can readily use this invention as a base to design or modify other processes and structures for implementing the same purposes and / or achieving the same advantages as the embodiments described herein. Those skilled in the art should also recognize that such equivalent constructions do not depart from the spirit and scope of the invention, and that various changes, substitutions, and modifications can be made to them herein without departing from the spirit and scope of the invention.

Claims

1. A thermal sensor, comprising: a single first temperature sensitive device comprising a single bandgap thermal sensing device adapted to generate a temperature dependent signal; a first current source connected to the first temperature sensitive device through a first switching device, the first current source being adapted to pass a first value of current through the bandgap thermal sensing device through the first switching device; a second current source connected to the first temperature sensitive device through a second switching device, adapted to pass a second value of current different from the first value through the bandgap thermal sensing device through the second switching device, the bandgap thermal sensing device being adapted to generate the temperature dependent signal in response to temperature and current at each of the first value and the second value; a signal processing circuit operably connected to the bandgap thermal sensing device through a third switching device and processing received temperature dependent signal using processing parameters to generate a processed signal when the signal processing circuit is connected to the bandgap thermal sensing device, wherein the signal processing circuit is connected in series with the third switching device and across the bandgap thermal sensing device; a controller adapted to operate the first switching device, the second switching device and the third switching device and to receive the temperature dependent signal alternately in response to current at the first value and in response to current at the second value and to generate an output signal indicative of the temperature from the temperature dependent signal and the processed signal, wherein the first switching device, the second switching device and the third switching device are adapted to be actuated in coordination to alternately connect the first current source and the second current source to the bandgap thermal sensing device and to connect the signal processing circuit to the bandgap thermal sensing device by turning on the third switching device when the first current source is connected to the bandgap thermal sensing device and to disconnect the signal processing circuit from the bandgap thermal sensing device by turning off the third switching device when the second current source is connected to the bandgap thermal sensing device.

2. The thermal sensor of claim 1, further comprising: an analog to digital converter, an input of the analog to digital converter being connected to the bandgap thermal sensing device, an output of the analog to digital converter being connected to the controller.

3. The thermal sensor of claim 2, the controller comprising a microcontroller unit.

4. The thermal sensor of claim 2, the bandgap thermal sensing device comprising a diode-connected transistor.

5. The thermal sensor of claim 4, the signal processing circuit and the third switching device being connected across the diode-connected transistor.

6. The thermal sensor of claim 4, an emitter of the diode-connected transistor being connected to an ADC unit.

7. The thermal sensor of claim 6, an output of the ADC unit being connected to the controller.

8. The thermal sensor of claim 3, wherein, the output signal indicative of the temperature being proportional to absolute temperature at the thermal sensor in a temperature range of -50°C to 150°C.

9. The thermal sensor of claim 8, wherein, Each temperature corresponding to the output signal within the temperature range differs from a temperature determined from a proportional relationship between the absolute temperature and the output signal by no more than 5°C.

10. The thermal sensor of claim 8, wherein, A linear approximation of the processed signal as a function of the absolute temperature over the entire temperature range has a first offset at 0K, and a linear approximation of the temperature dependent signal as a function of the absolute temperature over the entire temperature range has a second offset at 0K, and the first offset and the second offset are the same.

11. The thermal sensor of claim 1, wherein, The signal processing circuit comprises a continuous DC type amplifier.

12. The thermal sensor of claim 1, wherein, The bandgap thermal sensing device comprises a bipolar junction transistor, the first value of current is configured to generate a first current density in the bipolar junction transistor, the second value of current is configured to generate a second current density in the bipolar junction transistor, the first current density is different from the second current density.

13. The thermal sensor of claim 1, wherein, The bandgap thermal sensing device comprises a field effect transistor.

14. A method of temperature measurement, comprising: alternately turning on a first switching device and a second switching device to alternately connect a first current source and a second current source to a bandgap thermal sensing device, wherein the first current source is adapted to pass a first value of current through the bandgap thermal sensing device through the first switching device, and the second current source is adapted to pass a second value of current through the bandgap thermal sensing device through the second switching device; in response to a temperature and a current of each of the first value and the second value, the bandgap thermal sensing device generates a temperature dependent signal; operably connecting a signal processing circuit to the bandgap thermal sensing device by turning on a third switching device, and using a processing parameter to process the received temperature dependent signal to generate a processed signal when the signal processing circuit is connected to the bandgap thermal sensing device, wherein the signal processing circuit is connected in series with the third switching device and across the bandgap thermal sensing device; and generating an output signal indicative of the temperature based on the temperature dependent signal and the processed signal, wherein the first switching device, the second switching device, and the third switching device are adapted to be actuated in coordination, and the signal processing circuit is connected to the bandgap thermal sensing device by turning on the third switching device when the first current source is connected to the bandgap thermal sensing device, and the signal processing circuit is disconnected from the bandgap thermal sensing device by turning off the third switching device when the second current source is connected to the bandgap thermal sensing device.

15. The method of claim 14, wherein determining a temperature T comprises: obtaining a value of a third differential voltage dV0 at a single known temperature TO; and determining the temperature T as T = dV ∙ TO / dV0, where T and TO are measured in K.

16. The method of claim 14, the first switching device, the second switching device, and the third switching device are controlled by a controller.

17. The method of claim 16, the controller comprises a microcontroller unit.

18. The method of claim 14, the bandgap thermal sensing device comprising a diode-connected transistor.

19. The method of claim 18, the signal processing circuit connected across the diode-connected transistor.

20. The method of claim 14, wherein, the first value of current configured to generate a first current density in the bandgap thermal sensing device, the second value of current configured to generate a second current density in the bandgap thermal sensing device, the first current density different from the second current density.

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