Temperature correction circuit for reference voltage

Abstract

A temperature correction circuit for a voltage reference circuit includes two amplifiers each having an output that controls a respective transistor that generates a correction current for adjusting a reference voltage. Both amplifiers include one input coupled in a path to a reference voltage source and another input coupled in a path to a temperature sensing diode circuit. The output of one amplifier controls the conductivity of its respective transistor to adjust the reference voltage when the temperature exceeds a high temperature setpoint. The output of the other amplifier controls the conductivity of its respective transistor to adjust the reference voltage when the temperature is below a low temperature setpoint.

Description

Technical Field

[0001] This invention relates to a temperature correction circuit for a reference voltage. Background Technology

[0002] Reference voltages are used to provide stable and predictable voltages in electronic circuits. One type of reference voltage is the bandgap voltage. A bandgap voltage is generated by a bandgap reference circuit and is based on the bandgap of the semiconductor device within that circuit. Another type of reference voltage is the Zener reference voltage. A Zener reference voltage is generated by a Zener reference circuit that includes a Zener diode and is based on the breakdown voltage of that diode.

[0003] For circuits designed to operate over a wide temperature range, a reference voltage that remains relatively constant over the temperature range may be required. Summary of the Invention

[0004] Features specifically shown or described in one embodiment set forth herein may be implemented in other embodiments set forth herein.

[0005] In one embodiment, a circuit includes: a reference voltage source; an output coupled to the reference voltage source for providing a reference voltage; a temperature sensing diode circuit; a first amplifier having a first input coupled to a path to the reference voltage source and a second input coupled to a terminal of the temperature sensing diode circuit; a first transistor including a control terminal coupled to the output of the first amplifier and a first current terminal for providing a correction current for adjusting the reference voltage in response to the temperature sensing diode circuit indicating an excess of a first temperature; a second amplifier including a first input coupled to the reference voltage source and a second input coupled to the terminal of the temperature sensing diode circuit; and a second transistor including a control terminal coupled to the output of the second amplifier and a first current terminal for providing a correction current for adjusting the reference voltage in response to the temperature sensing diode circuit indicating a temperature below a second temperature.

[0006] In yet another embodiment, the second current terminal of the first amplifier is coupled to the first input of the first amplifier.

[0007] In another embodiment, when the temperature sensing diode circuit indicates that the temperature exceeds a first temperature, the first amplifier drives its output with a voltage to control the conductivity of the first transistor, such that the voltage of the first input of the first amplifier matches the voltage of the second input of the first amplifier.

[0008] In another embodiment, when the temperature sensing diode circuit indicates that the first temperature has not been exceeded, the first current terminal of the first transistor does not provide a correction current for adjusting the reference voltage.

[0009] In another embodiment, the first amplifier controls the amount of correction current generated by the first current terminal of the first transistor such that when the first temperature is exceeded, the change in the amount of correction current is positively correlated with the temperature change.

[0010] In another embodiment, the second current terminal of the second transistor is coupled to the second input of the second transistor.

[0011] In another embodiment, when the temperature sensing diode circuit indicates that the temperature is below the second temperature, the second amplifier drives its output with a voltage to control the conductivity of the second transistor, such that the voltage of the second input of the second amplifier matches the voltage of the first input of the second amplifier.

[0012] In another embodiment, in response to the temperature sensing diode circuit indicating that the temperature is not lower than the second temperature, the first current terminal of the second transistor does not provide a correction current for adjusting the reference voltage.

[0013] In another embodiment, the second amplifier controls the amount of correction current generated by the first current terminal of the second transistor such that when the temperature is lower than the second temperature, the change in the amount of correction current is positively correlated with the negative temperature change.

[0014] In another embodiment, the output is provided by a node in the output current path, wherein the correction current provided by the first current terminal of the first amplifier and the correction current provided by the first current terminal of the second amplifier are provided by a resistive circuit across the output current path to adjust the reference voltage.

[0015] In another embodiment, the circuit includes a resistive path from the reference voltage source to the power supply rail, wherein the first input of the first amplifier is coupled to a first node of the resistive path and the first input of the second amplifier is coupled to a second node of the resistive path, wherein the resistive circuit is located in the resistive path between the first node and the second node.

[0016] In yet another embodiment, the terminal of the temperature sensing diode circuit is coupled to the reference voltage source via a bias current path.

[0017] In yet another embodiment, the second input of the second amplifier is coupled to a node of the bias current path via at least one resistive circuit.

[0018] In another embodiment, the reference voltage source is characterized as a bandgap voltage source, and the reference voltage is characterized as a bandgap reference voltage.

[0019] In another embodiment, the reference voltage source is characterized as a Zener voltage source, and the reference voltage is characterized as a Zener reference voltage.

[0020] In yet another embodiment, the output is coupled to the reference voltage source via at least one resistive circuit.

[0021] In another embodiment, the temperature sensing diode circuit includes a bipolar transistor, the base of which is connected to its collector.

[0022] In another embodiment, the first current terminal of the first transistor and the first current terminal of the second transistor are connected together.

[0023] In another embodiment, at least one resistive circuit 503 is located in the path between the first current terminal of the first transistor and the first current terminal of the second transistor.

[0024] In another embodiment, the output is connected to a node in the current path from the reference voltage source to the power supply rail, wherein the correction current from the first current terminal of the first transistor and the correction current from the first current terminal of the second transistor are each provided by a resistive circuit in the current path located between the power supply rail and the node of the path.

[0025] In another embodiment, a circuit includes: a reference voltage source; an output path from the reference voltage source to a power supply rail; an output connected to a node of the output path for providing a reference voltage; a temperature-sensing diode circuit; a first amplifier having a first input coupled to a path to the reference voltage source and a second input coupled to a terminal of the temperature-sensing diode circuit; a first transistor including a control terminal coupled to the output of the first amplifier and a first current terminal for providing a correction current for adjusting the reference voltage in response to the temperature-sensing diode circuit indicating an excess of a first temperature; a second amplifier including a first input coupled to the path to the reference voltage source and a second input coupled to the terminal of the temperature-sensing diode circuit; and a second transistor including a control terminal coupled to the output of the second amplifier and a first current terminal for providing a correction current for adjusting the reference voltage in response to the temperature-sensing diode circuit indicating a temperature below a second temperature. A second current terminal of the first amplifier is coupled to the first input of the first amplifier, and a second current terminal of the second transistor is coupled to the second input of the second transistor.

[0026] In another embodiment, the output path includes a resistive circuit coupled in the path between the node and the power supply rail, wherein a correction current from the first current terminal of the first transistor, for adjusting the reference voltage in response to the temperature sensing diode circuit indicating that the temperature exceeds the first temperature, flows through the resistive circuit to adjust the reference voltage; and a correction current from the first current terminal of the second transistor, for adjusting the reference voltage in response to the temperature sensing diode circuit indicating that the temperature is below the second temperature, flows through the resistive circuit to adjust the reference voltage.

[0027] In another embodiment, when the temperature sensing diode circuit indicates a temperature exceeding a first temperature, the first amplifier drives its output with a voltage to control the conductivity of the first transistor, such that the voltage of the first input of the first amplifier matches the voltage of the second input of the first amplifier; and when the temperature sensing diode circuit indicates a temperature below a second temperature, the second amplifier drives its output with a voltage to control the conductivity of the second transistor, such that the voltage of the second input of the second amplifier matches the voltage of the first input of the second amplifier.

[0028] In another embodiment, when the temperature sensing diode circuit indicates that the temperature is not exceeded, the first current terminal of the first transistor does not provide a correction current for adjusting the reference voltage; and in response to the temperature sensing diode circuit indicating that the temperature is not lower than the second temperature, the first current terminal of the second transistor does not provide a correction current for adjusting the reference voltage. Attached Figure Description

[0029] The invention will be better understood by referring to the accompanying drawings, and many of its objectives, features and advantages will become apparent to those skilled in the art.

[0030] Figure 1 This is a voltage versus temperature graph showing a prior art bandgap voltage reference circuit.

[0031] Figure 2 This is a circuit diagram of a temperature correction circuit for a voltage reference circuit according to an embodiment of the present invention.

[0032] Figure 3 This is a graph illustrating the operation of a temperature correction circuit for a voltage reference circuit according to an embodiment of the present invention.

[0033] Figure 4 This is a circuit diagram of a temperature correction circuit for a voltage reference circuit according to an embodiment of the present invention.

[0034] Figure 5 This is a circuit diagram of a temperature correction circuit for a voltage reference circuit according to an embodiment of the present invention.

[0035] Figure 6 This is a circuit diagram of a prior art temperature correction circuit used in a bandgap voltage reference circuit.

[0036] Unless otherwise specified, the same reference numerals are used in different drawings to indicate the exact same object. The drawings are not necessarily drawn to scale. Detailed Implementation

[0037] The following is a detailed description of the modes used to carry out the invention. This description is intended to illustrate the invention and should not be considered limiting.

[0038] As disclosed herein, a temperature correction circuit for a voltage reference circuit includes two amplifiers, each having an output that controls a corresponding transistor to generate a correction current for adjusting a reference voltage. Both amplifiers include one input coupled to a path to a reference voltage source and another input coupled to a path to a temperature-sensing diode circuit. The output of one amplifier controls the conductivity of its corresponding transistor to adjust the reference voltage when the temperature exceeds a high-temperature setpoint. The output of the other amplifier controls the conductivity of its corresponding transistor to adjust the reference voltage when the temperature is below a low-temperature setpoint.

[0039] In some embodiments, a resistive voltage divider is implemented in a resistive path to generate a temperature setpoint voltage, which is compared with a temperature-dependent voltage to generate a correction current at temperatures above the high-temperature setpoint and below the low-temperature setpoint.

[0040] In some embodiments, a temperature correction circuit that utilizes two amplifiers and a control transistor to provide a correction current can provide a multi-temperature correction of the reference voltage while employing a lower accuracy circuit that is less sensitive to variations due to inadequate modeling, package shift, and other defects. Additionally, in some embodiments, the finite gain of the amplifiers can effectively "round off" the temperature correction to enhance performance. In some embodiments, this circuit can provide up to a 9x improvement in voltage correction.

[0041] The reference voltage can be adjusted to have a negligible linear variation with temperature, but can still have a residual quadratic (parabolic) variation with temperature. This parabolic variation can be minimized by adding a piecewise linear (PWL) correction, which is implemented by generating a correction current that depends on the temperature deviation above the high-temperature setpoint and a correction current that depends on the temperature deviation below the cold-temperature setpoint. There is no correction current at temperatures between the two setpoints.

[0042] Figure 1 This is a graph showing the bandgap voltage generated by a prior art bandgap reference circuit across an operating temperature range from -40 °C to 160 °C. Some bandgap reference circuits are modified to eliminate the linear change in bandgap voltage with respect to temperature, thus leaving an unavoidable second-order variation. This second-order variation in... Figure 1 The figure shows a parabolic variation of 5 mV over a temperature range from -40 °C to 160 °C, i.e., from a peak voltage of 800 mV in the middle range to 795 mV at the extreme temperature. Depending on the application, this voltage variation over the temperature range may be detrimental to the operation of circuits utilizing bandgap voltages.

[0043] Figure 6This is a circuit diagram of a prior art temperature compensation circuit 601, which provides a correction current (ICORRECTION) to increase the voltage of the output (not shown) of a bandgap reference circuit used for segmented correction when the temperature drops below a lower temperature setpoint or rises above a higher temperature setpoint, thereby increasing the bandgap voltage for these temperature ranges. The correction current ICORRECTION is generated by the current mirrors of NFETs 621 and 623 in response to a temperature exceeding a high temperature setpoint, or by the current mirrors of NFETs 639 and 641 in response to a temperature dropping below a cold temperature setpoint.

[0044] Circuit 601 includes a current comparator 605 for determining when the temperature exceeds a high-temperature setpoint and providing an inverse current (IHOT) indicating how much the temperature is higher than the high-temperature setpoint. The current comparator 605 includes a temperature-sensitive current source 611, current mirrors of NFETs 615 and 617, and a fixed current source 613 that sets the high-temperature setpoint with a fixed current. Figure 6 In the diagram, current source 611 represents the temperature sensing diode circuit and resistor (both not shown), which provides a current VBE / R that is inversely proportional to the temperature.

[0045] When the current VBE / R is higher than the fixed current ICH provided by current source 613 (indicating a temperature below the high-temperature setpoint), NFET 617 is biased to a conducting level to conduct a current greater than the fixed current ICH. Under this condition, the voltage at node 616 is pulled to ground, causing no current to flow through NFETs 621 and 623. With no current flowing through NFET 623, the current mirrors of PFETs 625 and 627 will not conduct current through PFET 627, causing the current IORRECTION to be 0 amperes (assuming NFET 639 is also not conducting due to the temperature being above the cold-temperature setpoint). Under this condition, circuit 601 does not provide the correction current attributable to current comparator 605.

[0046] As temperature increases, the current VBE / R decreases, thereby reducing the conductivity of NFET 617. When the conductivity of NFET 617 decreases to the point where it no longer conducts all the fixed current ICH, the voltage at node 616 will subsequently rise and NFETs 621 and 623 will become conductive. With NFET 623 conducting, the current mirrors of PFETs 625 and 627 will cause the ICRRECTION to rise above 0 amperes. When VBE / R < ICH, the current (IHOT) through NFET 621 will be equal to IC - VBE / R and will increase proportionally to the temperature increase above the temperature setpoint set by the fixed current ICH. The ICRRECTION current will also increase proportionally. Because the current ICRRECTION is supplied to the bandgap reference circuit (not shown), this current causes the bandgap voltage to increase proportionally to its current increase.

[0047] Circuit 601 includes a current comparator 607 for determining when the temperature is below a cryogenic setpoint and providing a correction current indicating the degree to which the temperature is below the cryogenic setpoint. The current comparator 607 includes a temperature-sensitive current source 631, current mirrors of NFETs 635 and 637, and a fixed current source 633 whose fixed current sets the cryogenic setpoint. Figure 6 In the diagram, current source 631 represents the temperature sensing diode circuit and resistor (both not shown), which provides a current VBE / R that is inversely proportional to the temperature.

[0048] When the fixed current ICC is higher than the current VBE / R supplied by current source 631 (indicating a temperature above the low temperature setpoint), NFET 637 is biased to a conducting level to conduct a current greater than the current VBE / R supplied by current source 631. Under this condition, the voltage at node 636 is pulled to ground, so that no current flows through NFETs 639 and 641. With no current flowing through NFET 639, the current mirrors of PFETs 625 and 627 will not conduct current through PFET 627, resulting in current IORRECTION at 0 amperes (assuming NFET 623 is also not conducting due to the temperature being below the high temperature setpoint). Under this condition, circuit 601 does not provide the correction current attributable to current comparator 607.

[0049] As the temperature decreases, the current VBE / R increases to the point where it provides more current than NFET 637 can conduct, since the conductivity of NFET 637 is set by a fixed current ICC. When current source 631 generates more current than NFET 637 can conduct, the voltage at node 636 rises to the point where NFETs 639 and 641 become conductive. With NFET 639 conducting, the current mirrors of PFETs 625 and 627 will cause the ICRRECTION to rise above 0 amps. When VBE / R (from current source 631) > ICC, the current through NFET 641 will be equal to VBE / R - ICC, and will increase inversely proportional to the temperature decrease below the low-temperature setpoint set by the fixed current ICC. The ICRRECTION current will also increase inversely to adjust the bandgap voltage. Because the current ICORRECTION is supplied to the bandgap reference circuit (not shown) and causes the bandgap voltage to increase proportionally to the increase of its current, the amount of voltage compensation for the bandgap voltage will change inversely with temperature when VBE / R (from current source 631) > ICC.

[0050] One issue is that circuit 601 uses current ICC and ICH to set the temperature setpoint, which can lead to accuracy problems and may consume a relatively large amount of current. It also uses current mirrors from PFETs 625 and 627, which may conduct extremely small currents and could also cause accuracy issues.

[0051] Figure 2 A temperature correction circuit 201 for a bandgap voltage reference circuit 200 according to an embodiment of the present invention is shown. Circuit 200 includes a bandgap voltage source 213, which includes an output providing a bandgap voltage RVI. The bandgap voltage source 213 generates a bandgap voltage (RVI) based on the bandgap of a semiconductor device (not shown) of the bandgap voltage source 213. In one embodiment, the undivided bandgap voltage generated by the voltage source 213 is typically 1.23V, but may have other voltages in other embodiments. An output current path 231 is coupled to the output of the voltage source 213 and includes resistors 233, 235, and 237 to generate a bandgap voltage (RVA) at node 234 of path 231, which is divided down to a desired value (e.g., 0.8V) that is useful for systems utilizing bandgap voltages. The bandgap voltage (RVA) at node 234 can be adjusted by the reference circuit 200 to compensate for temperature variations.

[0052] Circuit 201 includes a resistive current path 211 connected to the output of voltage source 213. Path 211 includes resistors 215, 217, and 219. Resistor 219 is connected to power rail 208, which in the illustrated embodiment is biased to a ground supply voltage, but in other embodiments may be biased to other supply voltages.

[0053] Circuit 201 includes a bias path 221 connected to the output of bandgap voltage source 213. Path 221 includes resistor 225 and diode 229. The voltage across diode 229 (the voltage at node 226 labeled TEMP) is the forward bias voltage of diode 229 that varies inversely with temperature. In some embodiments, the voltage across diode 229 varies at approximately -2mV / °C, but in other embodiments it may vary at other rates.

[0054] Circuit 201 includes an operational amplifier 203, which includes a non-inverting input connected to node 216 of path 211 and an inverting input connected to the terminal of diode 229 at node 226. The output of amplifier 203 is connected to the gate of NFET 207. The drain of NFET 207 is connected to the non-inverting input of amplifier 203 and to node 216 of path 211. The source of NFET 207 is connected to node 236 of path 231. The body bias terminal of NFET 207 is connected to rail 208. However, in other embodiments, the body bias terminal may be connected to node 236.

[0055] Circuit 201 includes an operational amplifier 205, which includes an inverting input connected to node 214 of path 211 and a non-inverting input connected to one end of resistor 227. The other end of resistor 227 is connected to node 226. The output of amplifier 205 is connected to the gate of NFET 209. The drain of NFET 209 is connected to the non-inverting input of amplifier 205 and to resistor 227. The source of NFET 207 is connected to node 236 of path 231. The body bias terminal of NFET 209 is connected to ground rail 208, but in other embodiments it may be connected to node 236.

[0056] In one embodiment, resistors 215, 217, 219, 227, 225, 233, 235, and 237 have resistances of 100K, 200K, 400K, 240K, 600K, 403K, 750K, and 50K, respectively. Bandgap voltage source 213 is designed to provide a maximum bandgap voltage of 1.23 V, and path 231 is designed to provide a bandgap voltage RVA of approximately 800 mV at node 234. However, in other embodiments, these voltages and resistances may have different values.

[0057] Figure 3 This is a graph showing the operation of circuit 200 across a temperature range of -40°C to 170°C. (Refer to...) Figure 3 The voltage and current description of the curve Figure 2 The operation of the circuit. For example... Figure 3 As shown, the voltage across diode 229 at node 226 (in Figure 3 The TEMP (labeled as TEMP) is generally linear and inversely proportional to temperature.

[0058] During operation, when the temperature is in the intermediate temperature range (e.g., approximately 38-90 °C), the voltage of the bandgap voltage source 213 ( Figure 2 (marked as RVI) near its maximum value (e.g., 1.23 V). Figure 3 This shows the voltage as a set fraction (e.g., approximately 2 / 3) of the voltage RVI. Figure 3 The set fraction (denoted as RVI) is determined by the ratio of the sum of the resistances of resistors 235 and 237 to the total resistance of resistors 233, 235, and 237, which in one embodiment is slightly less than two-thirds. Within this temperature range, the output voltage (RVA) of circuit 200 is approximately equal to the set fraction of RVI because circuit 200 does not provide a correction current across resistor 237 from NFET 207 or NFET 209. However, in other embodiments, RVA may have another fraction of RVI over an intermediate temperature range.

[0059] Return to view Figure 2 When the temperature is within this intermediate range, relative to the voltage at node 226, node 216 is at the voltage indicating the high-temperature setpoint. Figure 3 The curve shows the HOT TP and the voltage (COLD TB) at node 216, which indicates the low temperature setpoint. These voltage setpoints (HOT TP and COLD TP) indicate the temperature at which the temperature correction circuit 201 begins to adjust the voltage RVA when the temperature rises above the temperature indicated by HOT TP or falls below the temperature indicated by COLD TP.

[0060] When the temperature is in the middle range (or lower), the voltage at node 226 (labeled TEMP) is higher than the voltage at node 216. Figure 2 and Figure 3 (HOT in the context). Under this condition, the output voltage of amplifier 203 is driven to a low voltage value, causing NFET 207 to be non-conductive and not to provide correction current.

[0061] When the temperature rises above the temperature indicated by HOT TP, the voltage (TEMP) at node 226 becomes lower than the voltage at node 216. Because amplifier 203 is in a closed-loop feedback configuration, amplifier 203 drives the gate voltage of NFET 207 at the voltage at which NFET 207 begins to conduct, thereby reducing the voltage (HOT) at node 216 to match the voltage (TEMP) at node 226. When NFET 207 is conducting, it will correct the current (in Figure 3 A resistor (marked I207) is provided to resistor 237 to increase the voltage drop across resistor 237, thereby increasing the voltage of RVA to compensate for the decrease in voltage of RVI due to increased temperature. See also Figure 3 The diagram shows that the voltage of the setpoint fraction of RVI decreases as the temperature rises above 90 °C. The greater the temperature increase, the higher the output voltage of amplifier 203, causing NFET 207 to conduct to reduce HOT to match TEMP, where more correction current is supplied to resistor 237 to increase the voltage of RVA to compensate for the decrease in RVI at these temperatures. Therefore, the amount of correction current from NFET 207 ( Figure 3 The change in the correction current generated by NFET 207 increases proportionally to the temperature increase within this temperature range. Correspondingly, the amount of voltage correction also increases proportionally to the temperature increase. However, in some embodiments, the change in the correction current generated by NFET 207 will not necessarily be proportional to the temperature change when the temperature is above the temperature indicated by HOT TP, but will still be positively correlated with the temperature change to effectively adjust the bandgap voltage within the tolerance of the upper portion of the temperature range. If a change in one characteristic is proportional to a change in another characteristic, then it is also positively correlated with the change in said other characteristic.

[0062] When the temperature is above the cold temperature setpoint (COLD TP) indicated by the voltage at node 214, the voltage of TEMP is lower than the voltage at node 214 (COLD). At this time, the output voltage of amplifier 205 is low because the inverting input of amplifier 205 is at a higher voltage than the non-inverting input. Therefore, NFET 209 is not conducting, and no correction current is provided at the source of NFET 209. Furthermore, since NFET 209 is not conducting at this time, no current flows through resistor 227, and the voltage of DTEMP is approximately equal to the voltage at node 226 (TEMP).

[0063] However, once the temperature drops below the cold setpoint voltage (COLD TP) indicated by node 214, the voltages at node 226 (TEMP) and DTEMP rise above the COLD voltage. Because amplifier 205 is in a closed-loop feedback configuration, the output voltage of amplifier 205 rises to the point that NFET 209 becomes conductive, thereby pulling the DTEMP voltage to match the COLD voltage (and pulling the DTEMP voltage away from the TEMP voltage). The more the temperature drops below the cold temperature setpoint indicated by the voltage (COLD) at node 214, the higher the output voltage of amplifier 205 becomes, making NFET 209 more conductive and increasing the correction current through resistor 237 (in Figure 3 The larger the amount (denoted as I209), the higher the voltage of RVA, compensating for the decrease in RVI within this temperature range. In some embodiments, when the temperature is below the temperature setpoint of COLD TP, the current (I209) provided by NFET 209 changes proportionally to the negative temperature change. Therefore, under these conditions, the amount of voltage adjustment provided by the current from NFET 209 is proportional to the negative temperature change within this temperature range. In some embodiments, the change in the amount of correction current generated by NFET 209 will not necessarily be proportional to the negative temperature change, but will still be related to the negative temperature change to effectively adjust the bandgap voltage within the tolerance of this temperature range. If a change in one characteristic is proportional to a negative change in another characteristic, then it is also related to the negative change in said characteristic.

[0064] Therefore, circuit 201 provides a correction current that raises the bandgap voltage RVA for temperatures below the cold setpoint and for temperatures above the hot setpoint to compensate for the reduction in RVI voltage caused by operation within either of those edge temperature ranges. Thus, the voltage variation of RVA remains relatively flat over a large temperature range. Figure 3 As shown in the embodiments, the voltage of RVA changes by less than 1 mV within a temperature range from -40 °C to 160 °C.

[0065] The degree of voltage compensation of the bandgap voltage relative to the correction current (correction) can be adjusted by adjusting the resistance of the resistor in the current path 231. In some embodiments, the relative strength of the correction at temperatures above the thermal setpoint and below the cold setpoint can be adjusted by changing the resistance of resistor 227 relative to the resistances of resistors 215, 217, and 219.

[0066] As shown above, the voltage regulation operation provided by amplifier 203 and NFET 207 during hot temperatures and the voltage regulation operation provided by amplifier 205 and NFET 209 during cold temperatures are unidirectional because they only draw current when the temperature is above the hot setpoint (for amplifier 203) or below the cold setpoint (for amplifier 205).

[0067] Furthermore, in some embodiments, the finite gain of operational amplifiers 203 and 205 can be "rounded" to temperature correction to enhance performance. In some embodiments, a correction current is not generated immediately when the temperature crosses the setpoint because a small error voltage differential is required to conduct NFETs 207 and 209. The net effect is that the start of the correction current is not abrupt, but rather smoother. This can reduce variations in the reference voltage near the temperature setpoint. Additionally, in some embodiments, the amplifiers can be designed to further limit the gain to implement this feature more effectively.

[0068] In some embodiments, Figure 2 The resistor shown has similar temperature characteristics to the resistor in bandgap voltage source 213, which helps to make the correction current proportional or approximately proportional to temperature deviations outside the intermediate temperature range.

[0069] Figure 4 A circuit diagram of a temperature correction circuit 401 for a reference circuit 400 according to another embodiment is shown. It has a circuit diagram with... Figure 2 The items labeled in the attached diagrams are the same for the circuits.

[0070] Figure 4 Further details of an embodiment of operational amplifiers 203 and 205 according to one embodiment are shown. Figure 4 In this amplifier, amplifier 203 is implemented with current source 411 and PFETs 413 and 415, wherein the non-inverting input of amplifier 203 is connected to the gate of PFET 413 and the inverting input is connected to the gate of PFET 415. The body terminals of PFETs 413 and 415 are connected to the output (RVI) of bandgap voltage source 213. Amplifier 203 also includes current mirrors of NFETs 417 and 419, the body terminals and sources of which are connected to ground.

[0071] exist Figure 4 In this amplifier, amplifier 205 is implemented with current source 421 and PFETs 423 and 425, wherein the non-inverting input of amplifier 205 is connected to the gate of PFET 425 and the inverting input is connected to the gate of PFET 423. The body terminals of PFETs 423 and 425 are connected to the output (RVI) of bandgap voltage source 213. Amplifier 205 also includes current mirrors of NFETs 427 and 429, the body terminals and sources of which are connected to ground.

[0072] Also in Figure 4 In this embodiment, the diode temperature sensing circuit is implemented using a PNP transistor 405 in a diode configuration, wherein the base of the diode configuration is connected to its collector. In other embodiments, other types of diode temperature sensing circuits may be used, such as NPN transistors in a diode configuration. Furthermore, other embodiments may be implemented using other types of amplifiers.

[0073] Figure 5 A circuit diagram of a temperature correction circuit 501 for a voltage reference circuit 500 according to another embodiment is shown. It has... Figure 2 The same reference numerals are used for the same circuits. Voltage reference circuit 500 is characterized as a Zener reference circuit because reference voltage source 513 is a Zener diode voltage source including a Zener diode (not shown) and is based on the Zener diode's breakdown voltage. In one embodiment, the Zener diode's breakdown voltage is 5.1 volts, but in other embodiments it may have other voltages.

[0074] exist Figure 5 In this embodiment, the correction current (CORRECTIONC) from the amplifier NFET 209 is provided to the end of resistor 503, such that the correction current CORRECTIONC flows through resistor 503 and resistor 237. In contrast, the correction current from NFET 207 flows only through resistor 237.

[0075] Therefore, because the resistance through which the correction current CORRECTIONC flows (resistors 503 and 237) is greater than the resistance through which the correction current CORRECTIONH flows (resistor 237 only), current CORRECTIONC will provide a greater voltage correction to RVA than current CORRECTIONH. This configuration can be used when the output voltage of the Zener voltage source 513 changes at a greater rate with respect to temperature changes in the cooler temperature range than in the hotter temperature range. The amount of adjustment to RVA via CORRECTIONC and CORRECTIONH can be individually customized by setting the resistances of resistors 235, 503, and 237.

[0076] In other embodiments where the voltage output of voltage source 513 changes at a greater rate relative to temperature changes in a higher temperature range than temperature changes in a lower temperature range, CORRECTION H may be provided across resistors 503 and 537, and CORRECTION C may be provided only across resistor 237.

[0077] The temperature adjustment circuit described herein may be modified in other embodiments. For example, although Figure 2 , Figure 4 and Figure 5 The embodiment shows current from NFETs 207 and 209 applied to resistor 237, but in other embodiments, current from NFETs 207 and 209 can be applied to a current mirror that generates a mirrored current in path 231 to adjust the voltage of RVA. Furthermore, other types of transistors (e.g., PFETs, bipolar transistors) and other types of resistive circuitry can be used.

[0078] In other embodiments, the temperature setpoint can be designed to be at different values ​​by changing the resistance value of the resistor in path 211. For example, in some embodiments, the cold setpoint and the hot setpoint can be set at 33% and 67% of the temperature range, respectively. Thus, for a range of -40 °C to 175 °C, the cold setpoint would be at 32 °C and the hot setpoint would be at 103 °C. However, in other embodiments, the setpoint can be at other values, including other percentages. In some embodiments where the temperature setpoint is at 33% and 67% of the temperature range, a nine-fold reduction in parabolic variation can be achieved.

[0079] In some embodiments, at least some of the resistive circuitry may be programmable (e.g., resistors 215, 217, 233, 237) to program the maximum value of RVI to the temperature setpoint or the value of RVA.

[0080] One advantage of at least some embodiments of the temperature correction circuit described herein is that the correction voltage generated by the temperature correction circuit does not significantly depend on process parameters, nor does it require high-precision circuitry for generation. Furthermore, Figure 2 , Figure 4 and Figure 5 The temperature correction circuit includes only one temperature sensing diode circuit to determine both the hot and cold temperature setpoints, which reduces the number of devices in the circuit and the amount of current consumed.

[0081] Although temperature correction circuits 201 and 401 are shown and described for use in a bandgap reference circuit and temperature correction circuit 501 is shown for use in a Zener correction circuit, the temperature correction circuits described herein can be used with a Zener voltage source, a bandgap voltage source, or another type of reference voltage source.

[0082] The temperature regulation circuit shown and described herein can be used in any of a number of systems, such as computers, mobile phones, automotive electronics, wearable devices, IoT systems, industrial control equipment, embedded systems, or communication devices.

[0083] As used herein, an item is "coupled" to another item in a path by connecting to it or by being coupled to it through at least one other item in the current path. For example, in Figure 2 In this configuration, the drain of NFET 207 is coupled to the output of voltage source 213 via resistors 217 and 215. The drain of NFET 207 is also coupled to node 216 via a connection to node 216. The gate is the control terminal of the FET. The drain and source are the current terminals of the FET.

[0084] While specific embodiments of the invention have been shown and described, those skilled in the art will recognize that further changes and modifications can be made based on the teachings herein without departing from the invention and its broader aspects, and therefore the appended claims are intended to cover all such changes and modifications within the true spirit and scope of the invention.

Claims

1. A circuit, characterized in that, The circuit includes: Reference voltage source; The output is coupled to the reference voltage source and is used to provide a reference voltage. Temperature sensing diode circuit; A first amplifier has a first input coupled to a path to the reference voltage source and a second input coupled to a terminal of the temperature sensing diode circuit. A first transistor includes a control terminal coupled to the output of the first amplifier and a first current terminal for providing a correction current for adjusting the reference voltage in response to an indication from the temperature sensing diode circuit that a first temperature has been exceeded. A second amplifier, the second amplifier including a first input coupled to the reference voltage source and a second input coupled to the terminal of the temperature sensing diode circuit; The second transistor includes a control terminal coupled to the output of the second amplifier and a first current terminal for providing a correction current for adjusting the reference voltage in response to an indication by the temperature sensing diode circuit that the temperature is below a second temperature.

2. The circuit according to claim 1, characterized in that, The second current terminal of the first amplifier is coupled to the first input of the first amplifier.

3. The circuit according to claim 2, characterized in that, When the temperature sensing diode circuit indicates that the temperature exceeds the first temperature, the first amplifier drives its output with a voltage to control the conductivity of the first transistor, such that the voltage of the first input of the first amplifier matches the voltage of the second input of the first amplifier.

4. The circuit according to claim 1, characterized in that, When the temperature sensing diode circuit indicates that the temperature has not exceeded the first temperature, the first current terminal of the first transistor does not provide a correction current for adjusting the reference voltage.

5. The circuit according to claim 1, characterized in that, The first amplifier controls the amount of correction current generated by the first current terminal of the first transistor such that when the first temperature is exceeded, the change in the amount of correction current is positively correlated with the temperature change.

6. The circuit according to claim 1, characterized in that, The second current terminal of the second transistor is coupled to the second input of the second transistor.

7. The circuit according to claim 6, characterized in that, When the temperature sensing diode circuit indicates that the temperature is lower than the second temperature, the second amplifier drives its output with a voltage to control the conductivity of the second transistor, such that the voltage of the second input of the second amplifier matches the voltage of the first input of the second amplifier.

8. The circuit according to claim 1, characterized in that, In response to the temperature sensing diode circuit indicating that the temperature is not lower than the second temperature, the first current terminal of the second transistor does not provide a correction current for adjusting the reference voltage.

9. The circuit according to claim 1, characterized in that, The second amplifier controls the amount of correction current generated by the first current terminal of the second transistor such that when the temperature is lower than the second temperature, the change in the amount of correction current is positively correlated with the negative temperature change.

10. A circuit, characterized in that, The circuit includes: Reference voltage source; The output path from the reference voltage source to the power supply rail; An output, which is connected to a node in the output path to provide a reference voltage; Temperature sensing diode circuit; A first amplifier has a first input coupled to a path to the reference voltage source and a second input coupled to a terminal of the temperature sensing diode circuit. A first transistor includes a control terminal coupled to the output of the first amplifier and a first current terminal for providing a correction current for adjusting the reference voltage in response to an indication from the temperature sensing diode circuit that a first temperature has been exceeded. A second amplifier, the second amplifier including a first input coupled to the reference voltage source and a second input coupled to the terminal of the temperature sensing diode circuit; The second transistor includes a control terminal coupled to the output of the second amplifier and a first current terminal for providing a correction current for adjusting the reference voltage in response to an indication by the temperature sensing diode circuit that the temperature is below a second temperature. The second current terminal of the first amplifier is coupled to the first input of the first amplifier; The second current terminal of the second transistor is coupled to the second input of the second transistor.

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