LOW POWER AND LOW RESISTANCE BANDGAP CIRCUIT AND METHOD

Abstract

Circuit that features: a resistor (30); a diode (10) designed to conduct a diode current (I C ) to receive, so that a forward voltage (V) is present across the diode (10). BE ) occurs; a voltage divider (40) with a switched capacitor, which is connected to the diode (10) and is designed to reduce the forward voltage (V BE ) to receive and a scaled voltage (V BE / k), which is a fraction of the forward voltage (V BE ) is to be spent; a voltage-to-current converter (50) which is coupled between the voltage divider (40) with switched capacitor and the resistor (30) and which is designed to convert a resistance current (I CTAT ), which is proportional to the scaled voltage (V BE / k) and inversely proportional to a resistance (R CTAT ) of the resistance (30) is to be provided; and a current source (M1, M2) designed to supply the diode current (I C ) depending on the resistance current (I CTAT to provide.

Description

TECHNICAL AREA

[0001] This application concerns the field of bandgap voltage reference circuits and in particular a circuit for generating a current that is complementary to absolute temperature (CTAT) for a low-power bandgap circuit. BACKGROUND

[0002] Bandgap voltage reference circuits are widely used in voltage regulators and other integrated circuits. They generate a voltage that is essentially temperature-independent and corresponds to the theoretical bandgap of a semiconductor. This makes it possible to increase the performance of a circuit within a given temperature range.

[0003] Bandgap reference circuits are based on the sum of the currents of a current I. PTAT , which is proportional to the absolute temperature (“Proportional To Absolute Temperature”; PTAT current) and a current I CTAT, which is complementary to the absolute temperature (“Complementary To Absolute Temperature”; CTAT current). These PTAT and CTAT currents are generated by applying PTAT and CTAT voltages across reference resistors. Summing the two currents allows the temperature-dependent terms of the currents to be eliminated, thus obtaining a voltage that is essentially independent of temperature within the desired temperature range.

[0004] For low-power bandgap operations, such as those performed in a vehicle's idle (park) mode, very low CTAT currents are desirable. However, this requires the reference resistor to have a high resistance and therefore a large area.

[0005] The inventors aimed to provide a circuit for generating a CTAT current for a low-power bandgap reference that is capable of reducing both the current level and the resistance area.

[0006] Examples of bandgap voltage reference circuits are known from publications DE 10 2009 056 595 A1 and CN 1 16 257 111 A. OVERVIEW

[0007] The above-mentioned objective is achieved by the circuit according to claim 1, in particular by using a voltage divider with a switched capacitor arranged between a diode and the resistor of a CTAT circuit.

[0008] In one example, this disclosure relates to a circuit comprising a resistor and a diode. The diode is configured to receive a diode current, so that a forward voltage appears across the diode. The circuit further comprises a switched-capacitor voltage divider and a voltage-to-current converter. The switched-capacitor voltage divider is connected to the diode and is configured to receive the forward voltage and output a scaled voltage that is a fraction of the forward voltage. The voltage-to-current converter is coupled between the switched-capacitor voltage divider and the resistor and is configured to supply a resistive current that is proportional to the scaled voltage and inversely proportional to the resistance of the resistor.The circuit also includes a current source designed to provide the diode current depending on the resistance current.

[0009] In one example, the disclosure relates to a method comprising the following steps: supplying a diode current to a diode such that a forward voltage is present across the diode; generating a scaled voltage from the forward voltage by means of a voltage divider with a switched capacitor; and providing a resistance current that is proportional to the scaled voltage and inversely proportional to the resistance of a resistor, wherein the diode current depends on the resistance current. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] The embodiments described here can be better understood with the help of the following description and the drawings. The components in the figures are not necessarily to scale; rather, the focus is on illustrating the principles of the embodiments. Furthermore, identical reference numbers in the figures denote corresponding parts. In the drawings: Fig. Figure 1 shows an example of a bandgap reference circuit. Fig. Figure 2 shows a conventional example of a circuit for generating a current that is complementary to the absolute temperature (CTAT circuit). Fig. Figure 3 shows an example of a circuit structure for a CTAT circuit according to one or more techniques described here. Fig. Figure 4 shows another example of a circuit structure for a CTAT circuit according to one or more of the techniques described herein. Fig. Figure 5 shows a first example of a CTAT circuit in more detail. Fig. Figure 6 shows a second example of a CTAT circuit. Fig. Figure 7 shows a third example of a CTAT circuit. Fig. Figure 8 shows a fourth example of a CTAT circuit, which is a modified version of the tester from Fig. 7 is. Fig. Figure 9 shows an example of a bandgap reference generator according to one or more of the techniques described here, which derives the CTAT circuit from one of the Fig. 5 to 8 used. Fig. Figure 10 is a flowchart showing an example procedure for operating a CTAT circuit according to one or more techniques described in this disclosure. DETAILED DESCRIPTION

[0011] Fig. Figure 1 shows a general example of a bandgap reference voltage circuit 100, which is configured to provide a reference voltage v BG, which is essentially temperature-independent within a desired temperature range. The circuit includes a first circuit designed to generate a current I PTAT , which is proportional to the absolute temperature (PTAT circuit), and a second circuit designed to generate a current I CTAT , which is complementary to the absolute temperature (CTAT circuit), to generate. To generate the currents I PTAT and I CTAT To obtain the values, the PTAT and CTAT voltages are applied to corresponding reference resistors.

[0012] The circuit also features a first summing element designed to measure the PTAT current I PTAT and the CTAT stream I CTAT to sum up, in order to obtain a reference current applied across a resistor R. The voltage drop V RThe signal across resistor R is received as input by an amplifier controlled by a clock signal CK. The amplifier generates the desired bandgap voltage V. BG as output. The circuit can also include a second summing element that measures the currents I. PTAT and I CTAT summed up and provides a power output, exhibit.

[0013] Fig. Figure 2 shows an example of a conventional CTAT circuit 200 for generating a CTAT current I CTAT The circuit has a resistor 30 with a resistor R. CTAT and a diode 10 through which a current Ic flows, so that a forward voltage V is present across the diode 10 BE occurs. The forward voltage V BE This is referred to as the CTAT voltage. Diode 10 can be the base-emitter diode of a bipolar transistor and carry the forward voltage V. BEThis can therefore correspond to the base-emitter voltage of the bipolar transistor. The circuit also includes a current source that couples the diode 10 and the resistor 30. In the present example, the current source has a current mirror 70 configured to supply a resistive current I to the resistor 30. CTAT to supply and also the current Ic, which depends on the resistance current I CTAT to provide the flow through diode 10. A voltage drop across resistor R CTAT is essentially equal to the forward voltage V BE The resistance current I CTAT is therefore proportional to the forward voltage V BE and inversely proportional to the resistance R CTAT : I CTAT = V BE / R CTAT The transistors can be designed in such a way that the current Ic is equal to the current I. CTAT is.

[0014] Because it is based on a PN junction and uses a real resistor, the CTAT circuit shown is particularly robust. Furthermore, it is very easy to implement and does not require a precise clock signal.

[0015] However, the main disadvantage of this circuit is its power consumption. The CTAT voltage, which is typically the base-emitter voltage VCT, BE The voltage across a bipolar transistor typically ranges from 400 mV to 700 mV across PVT (Process, Voltage, Temperature). This results in resistance currents I. CTAT , which up to 700 mV / R CTAT can amount to.

[0016] For low-power bandgap operations, such as those required while a vehicle is idling (parked), the CTAT current must be very low. However, to achieve CTAT currents lower than 1 µA, the resistance of resistor 30 must be relatively high, e.g., higher than 1 MOhm. This means that resistor 30 occupies a large chip area. For example, the resistance of R CTAT -Resistance to obtain a CTAT current of 500 nA, for example, should be equal to 1.2 MOhm.

[0017] The conventional CTAT circuit is therefore based on a compromise between the R CTAT -value, which should be as low as possible, and the CTAT current, which also needs to be as low as possible.

[0018] Accordingly, the embodiments described here aim to solve this compromise problem, namely to provide a circuit capable of simultaneously reducing CTAT current and chip area. In particular, there is a need for a circuit that is robust under the desired operating conditions, namely a supply voltage from 3.3 V down to 2 V and a temperature range between -40 °C and 175 °C.

[0019] There are known solutions where a MOS transistor operating in weak inversion mode is used to provide the CTAT voltage, or where a MOS transistor operating in the linear region is used as a resistor. However, these solutions are not reliable under the operating conditions mentioned above.

[0020] Fig. Figure 3 shows an example of a circuit 300 that can be used in a CTAT circuit. The circuit includes a diode 10 and a resistor 30, which is a resistance R. CTAT A voltage divider 40 is arranged between the diode 10 and the resistor 30. The voltage divider 40 is designed to divide the CTAT voltage V. BE across diode 10 by a factor of k to V BE / k to reduce. Specifically, the voltage divider 40 is connected to the diode 10 and is designed to reduce the forward voltage V. BE to receive and a scaled voltage V BE / k, which is a fraction of the forward voltage V BE The circuit 300 further comprises a voltage-to-current converter 50, which is coupled between the voltage divider 40 and the resistor 30. The voltage-to-current converter 50 is configured to supply a resistive current I to the resistor 30. CTATto supply such that the voltage across resistor 30 is equal to the scaled voltage V BE / k is. The resistance current I CTAT is proportional to the scaled voltage V BE / k and inversely proportional to the resistance R CTAT of the resistor 30. This circuit therefore makes it possible to measure the current I CTAT to reduce the resistance by a factor k compared to the solution without a voltage divider. Consequently, it is also possible to reduce the resistance R. CTAT to reduce the resistance 30, since this reduction (at least partially) can be achieved by scaling the voltage V BE This can be compensated for by reducing the resistance R. CTAT This leads to a reduction in the chip space required for resistor 30 and therefore to a more compact assembly as well as lower power consumption.

[0021] According to one embodiment, the voltage divider 40 is a switched-capacitor voltage divider. A switched-capacitor voltage divider is a simple solution for generating a scaled voltage. However, the switching operations in the capacitive voltage divider can lead to glitches due to charge injection and clock feedthrough.

[0022] Fig. Figure 4 shows another example of a Circuit 400 that can be used in a CTAT circuit. This circuit can be considered an improvement / exemplary implementation of Circuit 300. Fig. 3. It features a voltage divider 40 with a switched capacitor. The circuit 400 further features an analog filter 60, which is connected between the voltage divider 40 with the switched capacitor and the voltage-to-current converter 50. The analog filter 60 is designed to smooth out the artifacts generated by the voltage divider operation in order to achieve the scaled voltage V. BE / k with reduced glitches. This smoothed, scaled voltage is then fed to the voltage-to-current converter 50.

[0023] Fig. Figure 5 shows a more detailed example of a CTAT 500 circuit for generating a CTAT current I CTAT This is one possible implementation of the example from Fig. 4. In addition to the points already mentioned regarding Fig. In addition to the four elements described, it also has a power source. The various elements of the circuit are described in more detail below.

[0024] In the illustrated example, the voltage divider 40 is implemented with a passive, charge-dividing capacitive array consisting of two capacitors. The voltage divider 40 with a switched capacitor has a first capacitor C1 with one end that can be connected to diode 10 via a first switch S1, and a second end that is connected to ground. The voltage divider 40 with a switched capacitor further has a second capacitor C2 with one end that can be connected in parallel to the first capacitor C1 via a second switch S2, and a second end that is connected to ground. The second capacitor C2 can either be connected to ground via a third switch S3 (to be discharged), or via a fourth switch S4 to an output of the voltage divider 40.The first capacitor C1 has a first capacitance C and the second capacitor C2 has a second capacitance (k-1) · C, which is greater by a factor (k-1) than the first capacitance C, where k is the division ratio of the <c ist. Der Spannungsteiler 40 weist auch einen Controller mit einem Taktphasengenerator, der in . Fig. 5 is not shown for the sake of simplicity. The controller is designed to perform the switching operations of the <c auf eine herkömmliche Weise zu steuern.

[0025] The voltage divider 40 with switched capacitor operates as follows:

[0026] During an initial period (Phase 1, as described in Fig. (as shown in 5) the first capacitor C1 is connected to the diode 10 via the first switch S1 and disconnected from the second capacitor C2 using the second switch S2, so that the forward voltage V BE a charge Q is applied to the first capacitor C1. The first capacitor C1 is therefore charged with a charge Q.VBE = C·V BE Charged. In the same phase, the third switch S3 is turned on and the fourth switch S4 is turned off, so that the second capacitor C2 is connected to ground at both ends. The second capacitor C2 is therefore completely discharged. The reference number "1" in the figure indicates which switches are turned on during the first phase.

[0027] During a second period (Phase 2, as described in Fig. (As shown in Figure 5), the first capacitor C1 is disconnected from diode 10 using the first switch S1 and connected to the second capacitor C2 via the second switch S2. The two capacitors are therefore connected in parallel, and the charge Q VBE The voltage across the capacitors is therefore divided between them. The voltage across the capacitors is thus Vx = Q VBE / (C+C(k-1)) = Q VBE / (kC)=V BE / k. Meanwhile, the third switch S3 is switched off and the fourth switch S4 is switched on. The voltage divider therefore provides a scaled voltage equal to V. BE / k is off. The reference number “2” in the figure indicates which switches are turned on during the second phase.

[0028] This process uses only passive components and requires no power input. The charge-sharing concept has the advantage of being insensitive to clock phase inaccuracies. However, the accuracy of the operation can be limited by capacitor matching and charge injection. Charge injection can be minimized by minimizing the size of the switching devices.

[0029] It is clear that the number of capacitors of the <c nicht auf zwei beschränkt ist und der Fachmann wüsste, wie weitere Kondensatoren in das obige Konzept zu implementieren wären. Das Erhöhen der Anzahl der Kondensatoren erhöht jedoch auch die Komplexität der Steuerung des Spannungsteilers.

[0030] In the illustrated example, the analog filter 60 is a two-stage passive RC low-pass filter, where each stage has a resistor R. F and a capacitor C F It features the two RC filter stages coupled in series. According to an example, the resistors R F This is implemented using high-impedance NMOS transistors operating in the linear region. Analog filter 60 is designed to suppress glitches in the scaled voltage V. BEto reduce / k, which is output by the voltage divider 40 with switched capacitor, and to output a smoothed scaled voltage to the voltage-to-current converter 50.

[0031] In the illustrated example, the voltage-to-current converter 50 comprises an operational amplifier 20 and a transistor M3. The input of the converter 50 is connected to the output of the analog filter 60 and therefore receives the smoothed, scaled voltage V. BE / k. One output of converter 50 is connected to the first end of resistor 30. Operational amplifier 20 and the third transistor M3 are coupled such that transistor M3 conducts a current I as a resistive current. CTAT , which is proportional to an input voltage V BE of the voltage-to-current converter, supplies and where the current I CTAT has such a level that the voltage drop I CTAT · R CTAT Across the resistance 30 equals V BE / k is. In the illustrated example, the resistance current I CTAT the same current as the one flowing through resistor 30 and is therefore equal to: I CTAT = V BE / (k·R CTAT The bandwidth of the operational amplifier 20 can be designed to be very small in order to eliminate any remaining switching artifacts in the smoothed scaled voltage V. BE / k to further reduce.

[0032] In the illustrated example, transistor M3 is an NMOS transistor. A first input of operational amplifier 20 receives the smoothed, scaled voltage V. BEA second input of operational amplifier 20 is connected to the source of transistor M3, which is also connected to resistor 30. The drain of transistor M3 is connected to the current mirror, and the source of transistor M3 is connected to the first end of resistor 30. An output of operational amplifier 20 is connected to the gate of transistor M3.

[0033] Circuit 500 also features the current mirror, which is designed to display the diode current Ic as a function of the resistance current I. CTAT to provide. In the illustrated example, the current source has a current mirror with a first transistor M1 coupled to diode 10, and a second transistor M2 coupled to resistor R. CTATThe first transistor M1 (current mirror output branch) and the second transistor M2 (current mirror input branch) are configured to produce a copy of the resistance current I as the diode current Ic. CTAT To provide. According to one example, transistors M1 and M2 are PMOS transistors. In the illustrated example, the source electrodes of the two transistors M1 and M2 are connected to each other and to a power supply. Furthermore, the gate electrodes of the two transistors M1 and M2 are connected to each other. A drain electrode of the first transistor M1 is coupled to diode 10, and a drain electrode of the second transistor M2 is coupled to resistor 30 and transistor M3 of the voltage-to-current converter. According to another example, transistors M1 and M2 are identical, and the diode current Ic is equal to the resistor current I. CTAT .

[0034] This circuit makes it possible to measure both the resistance current ICTAT as well as the resistance R CTAT to reduce resistance by 30. This reduction comes at the cost of introducing two active blocks.

[0035] The first active block is the clock phase generator for the voltage divider 40 with a switched capacitor (not shown). If the full-bandgap circuit already has a clock phase generator, it can be used for the CTAT circuit. Otherwise, it must be added. Since the concept of the <c jedoch auf Ladungsteilung beruht und da die Schaltung sehr niederfrequente Spannungen (oder sogar DC-Spannungen) verwendet, muss der Taktgenerator in Bezug auf die Frequenzgenauigkeit oder den Phasenjitter nicht präzise sein. Das bedeutet, dass es möglich ist, einen Oszillator mit sehr geringer Leistung wie etwa einen strombegrenzten Ringoszillator zu verwenden. Dieser Oszillator kann dann auch für andere Blöcke der Full-Bandgap-Spannungsreferenzschaltung verwendet werden.

[0036] The second active block is the operational amplifier 20 of the voltage-to-current converter 50. As mentioned above, the bandwidth of the operational amplifier 20 can be designed such that the artifacts in the scaled input voltage V BE The / k value can be reduced. It is therefore possible to use an operational amplifier with a very small bandwidth and very low power consumption.

[0037] In the example of Fig. In the voltage divider 40 with a switched capacitor, only passive elements are used, and the clock for the switching operations does not need to be precise. Furthermore, glitches caused by the switching operations of the <c eingebracht werden können, durch den analogen Filter 60 und durch die Verwendung eines Operationsverstärkers 20 in dem Spannungs-Strom-Wandler 50, der eine kleine Bandbreite hat, geglättet werden.

[0038] Since the circuit of Fig. 5 the scaled-down forward voltage VBE When / k is applied to resistor 30, it is possible to measure both the CTAT current I CTAT as well as the resistance value R CTAT to reduce the resistance of 30 compared to the solution without a voltage divider. For example, if the scaling factor k is equal to 4, it is possible to reduce the CTAT current I CTAT to reduce by two and the resistance R CTAT to reduce by two, compared to the circuit in Fig. 2. According to an example, the resistance R CTAT assumed to be 600 kOhms, which is half the value of the resistance in the example of Fig. 2 is. The current I CTAT This is then equal to 250 nA, which is also half the value of the current in the example of Fig. 2 is.

[0039] In the example of Fig. 5 is the current mirror (which in the illustrated example is composed of M1 and M2) with a voltage source (supply voltage V). DD) or a power source (supply current I) BIAS ) connected, while diode 10 and resistor 30 are connected to ground. However, it is clear that this situation can be reversed without changing the rest of the circuit or losing any of its advantages.

[0040] The CTAT circuit of Fig. 5 can be embedded in a full-bandgap voltage reference circuit, as in Fig. Figure 1 shows such a full-bandgap voltage reference circuit using the CTAT current I. CTAT The CTAT circuit is used for various bandgap operations. Therefore, it is important to be able to source or sink an output current from the CTAT circuit.

[0041] Fig. Figure 6 shows another example of a CTAT current circuit 600 that is capable of producing an output current I OUTPto produce. Compared to the circuit of Fig. Circuit 600 has an additional transistor M at position 5. OUTP , which is arranged in a current mirror configuration with the second transistor M2 of the current mirror. The control electrodes of transistors M2 and M OUTP are connected to each other and are the source electrodes of transistors M2 and M OUTP are connected to each other. In the example shown, the other transistor is M. OUTP a PMOS transistor. The other transistor M OUTP is designed to measure the current I flowing through transistor M2 CTAT to reflect, so that the output current I OUTP , which is further enhanced by transistor M OUTP flows, proportional to the current I CTAT is. The output current I OUTP It can then be used for further bandgap operations. This solution changes the operation of the CTAT circuit, which controls the current I. CTATprovides and offers a reliable output current, but not in the first place. That is to say, apart from the additional transistor M OUTP is the circuit of Fig. 6 the same as the example from Fig. 5.

[0042] Fig. Figure 7 shows another example of a CTAT current circuit 700 that is capable of producing an output current I OUTN to sink. Compared to the circuit of Fig. The voltage-current converter 50 also has an output transistor M. OUTN , which is connected in a current mirror configuration with the other transistor M3 of the voltage-to-current converter 50. In the illustrated example, both transistor M3 and the output transistor M OUTN NMOS transistors. In particular, a gate electrode of the output transistor M OUTN connected to a gate electrode of transistor M3 of the voltage-current converter and a source electrode of the output transistor MOUTN is connected to the source electrode of transistor M3. This connects transistors M3 and M OUTN They are controlled in the same way and have the same gate-source voltage. The output current I OUTN is therefore proportional to the resistance current I CTAT . Both the current I CTAT , which flows through transistor M3, as well as the current I OUTN , which is through the output transistor M OUTN The current flows, and also flows through the resistance 30, so that the total current I RCTAT , which flows through resistor 30, is equal to: I RCTAT = I CTAT + I OUTN Since the voltage drop V BE / k across resistor 30 by adding the output transistor M OUTN The resistance R is not changed. CTAT of resistance 30 equals: R CTAT = (V BE / k) / (I CTAT + I OUTN ). By adding the output transistor M OUTNIs it therefore possible to use a resistor with a reduced resistance value R? CTAT to use and therefore reduce the chip area required for resistor 30. The output current I OUTN It can then be used for further bandgap applications. Apart from the additional transistor M OUTN is the circuit in Fig. 7 the same as the example of Fig. 5. As in the example of Fig. 5 is the resistance current I RCTAT = I CTAT + I OUTN proportional to the scaled voltage V BE / k and inversely proportional to the resistance R CTAT of the resistance 30. The transistor currents I CTAT and I OUTN are also proportional to each other.

[0043] Fig. Figure 8 shows another example of a CTAT 800 current circuit, which is a modification / extension of the circuit from Fig. 7 is. Compared to the circuit of Fig. In diagram 7, circuit 800 features not just one output transistor, but two output transistors, M4 and M5. The first output transistor, M4, corresponds to output transistor M5. OUTN from Fig. 7, and a first output current I4 flows through it. The second output transistor M5 is connected to the first output transistor M4 in a mirror configuration. Each output current I4, I5 is proportional to the resistive current I. CTAT and can be used for various bandgap operations. Both the first output current I4 and the second output current I5 flow through resistor 30. The total current flowing through resistor 30 is I RCTAT is therefore: I RCTAT = I CTAT + I4 + I5. It is therefore possible to determine the resistance value R. CTAT to further reduce the resistance 30. For example, the scaling factor k is 4 and transistors M4 and M5 are chosen such that the resistance value R CTATwhich is equal to 240 kOhms and the current I RCTAT The current flowing through resistor 30 is equal to 250 nA. Compared to the example of Fig. 2. The current value can be reduced by 50% and the resistance value can be reduced to 20% of the original value. The addition of output transistors M4 and M5 can result in a lower resistance value R. CTAT , which requires less chip area, thus leading to a more compact structure. As in the previous example, the resistance current I RCTAT =I CTAT + I4 + I5 proportional to the scaled voltage V BE / k and inversely proportional to the resistance R CTAT of the resistance 30. The transistor currents I CTAT , I4 and I5 are also proportional to each other.

[0044] It is clear that the number of additional output transistors is not limited to two and that a person skilled in the art would determine an optimal number of output transistors for the circuit of Fig. 5 can be added, determining the output transistors in the same way as in the Fig. 7 and Fig. 8 can be connected.

[0045] Fig. Figure 9 shows an example of a full-bandgap reference voltage circuit 900, in which the CTAT circuits of the Fig. 5 to 8 can be used. Compared to the circuit of Fig. The bandgap reference voltage circuit 900 further features the aforementioned limited-current oscillator, which provides the clock signal for the switched-capacitor voltage divider. Since such a voltage divider is based on the concept of charge division, the clock phase generator does not need to be particularly precise, thus making it possible to use a limited-current oscillator. In addition, the circuit features a low-power current generator designed to provide a reference current I. BIAS to generate the necessary voltage for the oscillator and the CTAT circuit. This allows the Full-Bandgap Reference Voltage Circuit 900 to have very low power consumption.

[0046] Fig. Figure 10 is a flowchart showing an example process 1000 for operating a circuit to generate a CTAT current. The example process 1000 can be used to operate the devices described in this disclosure, such as the circuits according to the Fig. To operate 5 to 8.

[0047] Process 1000 involves supplying a diode current I C to a diode 10, so that a forward voltage V is applied across the diode BE occurs (step 1010). The current Ic can be supplied by a current source. In one example, the current Ic is supplied by a current mirror, which has two transistors arranged in a mirror configuration. In another example, diode 10 is the diode of a bipolar transistor and the forward voltage V BE is the base-emitter voltage of the bipolar transistor.

[0048] Process 1000 continues to demonstrate the generation of a scaled voltage V BE / k from the forward voltage V BE through a voltage divider 40 with a switched capacitor, where k is the scaling factor of the voltage divider 40 (step 1020). In one example, the voltage divider 40 with switched capacitor is connected to the diode 10 and receives the forward voltage V. BE The voltage divider 40 with a switched capacitor is connected to a controller with a clock phase generator, which controls the operation of the voltage divider 40. During an initial period, a first capacitor C1 of the <c über einen ersten Schalter S1 mit der Diode 10 verbunden, um die Vorwärtsspannung V BEto apply a charge C·V to the first capacitor C1. Simultaneously, a second capacitor C2 of the switched-capacitor voltage divider is disconnected from the first capacitor C1 using a second switch S2 and connected to ground by a third switch S3. Therefore, the first capacitor C1 is initially charged with a charge C·V. BE The first capacitor, C1, is charged, with C being the capacitance of the first capacitor, and the second capacitor, C2, is discharged. During a second period, the first capacitor, C1, is disconnected from diode 10 using the first switch, S1, and the second capacitor, C2, is connected to the first capacitor, C1, via the second switch, S2. The charge is therefore distributed between capacitors C1 and C2. The second capacitor, C2, has a second capacitance (k-1)*C, so the voltage drop across the capacitors is V. BE / k is the scaled voltage V. BE / k is the output signal of the voltage divider 40 with a switched capacitor.

[0049] Process 1000 also features the provision of a resistance CTAT current I CTAT , which is proportional to the scaled voltage V BE / k and inversely proportional to a resistance value R CTAT of a resistor 30, on (step 1030). The resistance current I CTAT The voltage is provided by a voltage-to-current converter 50, which is connected to the output of the voltage divider 40 with a switched capacitor. The voltage-to-current converter includes an operational amplifier 20 and a transistor M3, through which a current I is drawn. CTAT The current flows. Transistor M3 is connected to resistor 30 and supplies the current I. CTAT to resistor 30. Since the voltage across resistor 30 is equal to the scaled voltage V BE / k is, the current flowing through the resistor 30 is equal to V BE / (k·R CTAT). In one example, the resistance current I CTAT equal to the current V BE / (k·R CTAT ), which flows through resistor 30. In another example, the resistance current I CTAT proportional to the current flowing through resistor 30. The current I CTAT The current flowing through transistor M3 of the voltage-to-current converter 50 is reflected by the current mirror to provide the diode current Ic. The diode current Ic therefore depends on the current I. CTAT From. In one example, the diode current Ic is equal to the current I. CTAT Since the current flowing through resistor 30 is reduced, the power consumption can be lowered. Furthermore, it is possible to use a resistor 30 with a lower resistance value to obtain a more compact assembly.

[0050] In one example, the artifacts caused by the switching operations of the voltage divider 40 with a switched capacitor are smoothed by a filter 60, in particular an analog passive filter, which is arranged between the voltage divider 40 with a switched capacitor and the voltage-to-current converter 50. Furthermore, the operational amplifier 20 of the voltage-to-current converter 50 can be a narrow-band operational amplifier that absorbs the artifacts of the scaled voltage V. BE / k further reduced, be.

[0051] In one example, the current flowing through resistor 30 is I RCTAT the sum of the current flowing through transistor M3 I CTAT and at least one other stream I OUTN , I4, I5, which is passed through an output transistor M OUTN Current flows between M4 and M5 of the voltage-to-current converter 50. At least one output transistor M OUTNM4, M5 is connected to the main transistor M3 of the voltage-current converter 50 in a mirror configuration. The output currents I OUTN I4, I5 are proportional to the resistance current I CTAT and can be used for further bandgap operations. Since adding the output current increases the total current flowing through resistor 30, it is still possible to change the resistance value R. CTAT to further reduce the resistance by 30.

[0052] This application describes the use of a switched-capacitor voltage divider in a circuit to provide a CTAT current. This circuit is designed for use in a bandgap voltage reference circuit and typically includes a diode and a resistor. The current flowing through the resistor is proportional to the CTAT current. According to the application, the switched-capacitor voltage divider is connected between the diode and the resistor. Because the switched-capacitor voltage divider provides a scaled voltage across the resistor, it is possible to reduce both the CTAT current and the resistance value of the resistor. This allows for low power consumption and a reduction in the chip area allocated to the resistor, resulting in a more compact assembly.The switched-capacitor voltage divider has only passive components and does not require a precise clock. Switching artifacts in the scaled voltage can be smoothed by using a passive analog filter and a voltage-to-current converter with a narrow-bandwidth operational amplifier. The resulting circuit has very low power consumption and can be used for low-power, bandgap applications.

[0053] Although various embodiments relating to one or more specific implementations have been presented and described, changes and / or modifications may be made to the examples shown without altering the intent and scope of the features and structures mentioned herein. In particular, with regard to the various functions performed by the components or structures (units, assemblies, devices, circuits, systems, etc.) described above, the terms (including any reference to a “means”) used to describe such components shall, unless otherwise specified, correspond to any component or structure that performs the specified function of the component described (e.g.,which is functionally equivalent), even if it is not structurally equivalent to the disclosed structure that performs the function in the exemplary implementations of the present disclosure shown here.

Claims

[1] Circuit which features: a resistor (30); a diode (10) designed to conduct a diode current (I C ) to receive, so that a forward voltage (V) is present across the diode (10). BE ) occurs; a voltage divider (40) with a switched capacitor, which is connected to the diode (10) and is designed to reduce the forward voltage (V BE ) to receive and a scaled voltage (V BE / k), which is a fraction of the forward voltage (V BE ) is to be spent; a voltage-to-current converter (50) which is coupled between the voltage divider (40) with switched capacitor and the resistor (30) and which is designed to convert a resistance current (I CTAT ), which is proportional to the scaled voltage (V BE / k) and inversely proportional to a resistance (R CTAT ) of the resistance (30) is to be provided; and a current source (M1, M2) designed to supply the diode current (I C ) depending on the resistance current (I CTAT to provide. [2] Circuit according to claim 1, wherein the diode (10) is the diode of a bipolar transistor, wherein the forward voltage (V BE ) is a base-emitter voltage of the bipolar transistor. [3] Circuit according to claim 1 or 2, wherein the power source comprises: a first transistor (M1) coupled to the diode (10), and a second transistor (M2) coupled to the resistor (30), wherein the first transistor (M1) and the second transistor (M2) form a current mirror designed to act as a diode current (I C ) a copy of the resistance current (I CTAT ) to deliver, form. [4] Circuit according to one of claims 1 to 3, wherein the voltage divider (40) with switched capacitor comprises a controller, a first capacitor (C1), a second capacitor (C2) which can be coupled in parallel to the first capacitor (C1), the controller is trained to: during a first period: to connect the first capacitor (C1) to the diode (10) via a first switch (Si) in order to increase the forward voltage (V BE ) to apply to the first capacitor (C1), to disconnect the second capacitor (C2) from the first capacitor (C1) using a second switch (S2) and to connect it to ground using a third switch (S3), and During a second period: disconnect the first capacitor (C1) from the diode (10) using the first switch (Si) and connect the second capacitor (C2) to the first capacitor (C1) via the second switch (S2). [5] Circuit according to claim 4, wherein the first capacitor (C1) has a first capacitance and the second capacitor (C2) has a second capacitance which is greater by a factor (k-1) than the first capacitance, where k is the division ratio of the voltage divider (40) with the capacitor switched on. [6] Circuit according to any one of claims 1 to 5, further comprising an analog filter (60) connected between the switched-capacitor voltage divider (40) and the voltage-to-current converter (50), configured to smooth the artifacts generated by operations of the switched-capacitor voltage divider (40) in order to reduce the scaled voltage (V BE to generate / k). [7] Circuit according to one of claims 1 to 6, wherein the voltage-to-current converter (50) comprises an operational amplifier (20) and a third transistor (M3), wherein the operational amplifier (20) and the third transistor (M3) are coupled such that the third transistor (M3) provides a current (I) as a resistive current CTAT ), which is proportional to an input voltage (V BE / k) of the voltage-to-current converter (50) is, delivers. [8] Circuit according to claim 7, further comprising at least one output transistor (M OUTN ) has at least one output transistor (M OUTN ) is connected to the third transistor (M3) of the voltage-to-current converter (50) in such a way that they form a current mirror configured to produce an output current (I OUTN ), which is a copy of the resistance current (I CTAT ) is to be provided. [9] Full-bandgap reference circuit, which features: the circuit according to one of claims 1 to 8, and another circuit designed to carry a current (I PTAT ), which is proportional to an absolute temperature in a resistor, to output, where the full-bandgap reference circuit is designed to measure the resistance current (I CTAT ) and the current output by the further circuitry (I PTAT to sum them up. [10] Method (1000) which exhibits: Supplying (1010) a diode current (I C ) to a diode (10), so that a forward voltage (V) is applied across the diode (10) BE ) occurs, Generating (1020) a scaled voltage (V) BE / k) from the forward voltage (V BE ) by a voltage divider (40) with a switched capacitor; Providing (1030) a resistance current (I CTAT ), which is proportional to the scaled voltage (V BE / k) and inversely proportional to a resistance (RCTAT ) of a resistor (30) is, where the diode current (I C ) of the resistance current (I CTAT depends. [11] The method of claim 10, further comprising: During an initial period, a first capacitor (C1) of the voltage divider (40) with switched capacitor is connected to the diode (10) via a first switch (S1) to reduce the forward voltage (V BE ) to apply to the first capacitor (C1), disconnect a second capacitor (C2) of the voltage divider (40) with switched capacitor from the first capacitor (C1) using a second switch (S2), and connect the same to ground via a third switch (S3), and During a second time, disconnect the first capacitor (C1) from the diode (10) using the first switch (Si) and connect the second capacitor (C2) to the first capacitor (C1) via the second switch (S2).

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