A low voltage bandgap reference voltage circuit without curvature compensation

Abstract

The present invention discloses a low-voltage bandgap reference voltage circuit without curvature compensation, comprising: a current source, a low-voltage loop oscillator, a charge pump, a clock amplitude converter, a voltage generator inversely proportional to absolute temperature, and a voltage generator directly proportional to absolute temperature; the current source generates a bias current; the clock signal output by the low-voltage loop oscillator is used as the input clock signal of the charge pump, and the charge pump obtains a voltage-multiplied output clock and a DC voltage, which are input into the clock amplitude converter to obtain a two-phase clock; the two-phase clock inputs a voltage generator inversely proportional to absolute temperature to obtain a voltage inversely proportional to absolute temperature; the voltage inversely proportional to absolute temperature is input into a voltage generator directly proportional to absolute temperature to obtain a reference voltage output. The present invention broadens the normal operating temperature range of the circuit and improves the power supply rejection ratio under the condition of low power supply voltage and no curvature compensation.

Description

Technical Field

[0001] The invention relates to the field of integrated circuits, and in particular to a low-voltage bandgap reference voltage circuit without curvature compensation. Background Art

[0002] A reference voltage that is insensitive to power supply voltage, process, and temperature (PVT) changes is required for almost all circuit systems, such as low-dropout linear regulators (LDOs), DC-DC converters, digital-to-analog converters (DACs), and analog-to-digital converters (ADCs). In addition, since wearable smart devices and implantable medical devices often operate at power supply voltages of several hundred millivolts, it is necessary to study the design of low-voltage bandgap reference voltages.

[0003] The traditional current-mode bandgap reference circuit can operate below 1V, but due to the limitations of the base-emitter voltage of the bipolar junction transistor (BJT) and the overdrive voltage of the MOS tube, it is difficult to make a breakthrough in its minimum operating voltage. At present, one of the research directions of low-voltage bandgap reference voltage is to use the method of combining charge pumps with switched capacitors to achieve low-voltage and low-power design. However, due to the leakage current, clock feedthrough, and charge injection of the switched capacitor circuit, the operating temperature range and power supply rejection ratio of the bandgap reference voltage circuit of this structure are severely limited. Therefore, in order to improve the performance of the low-voltage bandgap reference circuit with a switched capacitor structure, the circuit structure still needs to be further optimized. Summary of the invention

[0004] In view of the deficiencies of the prior art, the present invention provides a low-voltage bandgap reference voltage circuit with high power supply rejection ratio, wide operating temperature range and no curvature compensation.

[0005] The specific technical solutions are as follows:

[0006] A low-voltage bandgap reference voltage circuit without curvature compensation comprises: a current source, a low-voltage ring oscillator, a charge pump, a clock amplitude converter, a voltage generator inversely proportional to absolute temperature, and a voltage generator proportional to absolute temperature;

[0007] The power supply voltage is input into the current source to generate a bias current; the input of the low-voltage ring oscillator is the power supply voltage and the bias current, and the output is a clock signal; the input of the charge pump is the power supply voltage and the clock signal output by the low-voltage ring oscillator, the charge pump doubles the input power supply voltage and the amplitude of the input clock signal, and the output of the charge pump is a DC voltage and a clock signal; the input of the clock amplitude converter is the bias current, the output clock of the charge pump and the DC voltage, and the output is a two-phase clock whose amplitude does not change with the power supply voltage; the input of the voltage generator inversely proportional to the absolute temperature is the two-phase clock, the bias current, and the DC voltage output by the charge pump, and the output is a voltage inversely proportional to the absolute temperature; the input of the voltage generator proportional to the absolute temperature is the voltage inversely proportional to the absolute temperature, the bias current, and the DC voltage output by the charge pump, and the output is a reference voltage;

[0008] The clock amplitude converter includes: a bipolar junction transistor, a capacitor, and two inverters arranged in parallel. The bias current generated by the current source is input into the clock amplitude converter, and the output of the first inverter is used as the input of the second inverter. The outputs of the two inverters are two-phase clocks output by the clock amplitude converter.

[0009] Furthermore, the voltage generator inversely proportional to the absolute temperature comprises: a bipolar junction transistor, three capacitors of the same specification, one capacitor at the output end, and eight switches, all of which adopt a CMOS structure; the current source is connected to the emitter of the BJT, the base of the BJT is connected to the collector and grounded; the switch S1 is located between the emitter of the BJT and the left plate of the capacitor C1; the switch S2 is located between the right plate of the capacitor C1 and the left plate of the capacitor C2; the switch S3 is located between the right plate of the capacitor C2 and the left plate of the capacitor C3; the switch S4 is located between the right plate of the capacitor C1 and the ground; the switch S5 is located between the right plate of the capacitor C2 and the ground; the switch S6 is located between the left plate of the capacitor C1 and the output end CTAT; the switch S7 is located between the left plate of the capacitor C2 and the output end CTAT; the switch S8 is located between the left plate of the capacitor C3 and the output end CTAT; the upper plate of the capacitor C4 is connected to the output end CTAT, and the lower plate of the capacitor C4 is connected to the ground.

[0010] Furthermore, when the positive input clock of the voltage generator inversely proportional to the absolute temperature is at a high level, switches S1, S2, and S3 are turned on, and switches S4, S5, S6, S7, and S8 are turned off. At this time, capacitors C1, C2, and C3 are connected in series in sequence and in parallel with the bipolar junction transistor. Since C1 = C2 = C3, the voltage drops of capacitors C1, C2, and C3 are all

[0011] When the positive input clock of the voltage generator inversely proportional to the absolute temperature is at a low level, switches S1, S2, and S3 are disconnected, and switches S4, S5, S6, S7, and S8 are turned on. At this time, capacitors C1, C2, and C3 are connected in parallel, and capacitors C1, C2, and C3 charge capacitor C4. The voltage of capacitor C4 finally stabilizes at

[0012] Furthermore, in a voltage generator that is inversely proportional to absolute temperature, the amplitude V of the positive input clock h Should meet:

[0013]

[0014] Where V BE V is the voltage with a negative temperature coefficient obtained after the bias current flows through the bipolar junction transistor. thn is the threshold voltage of the NMOS in the switch, V thp is the threshold voltage of the PMOS in the switch.

[0015] Furthermore, the charge pump doubles the input power supply voltage by 2 times and doubles the amplitude of the input clock signal by 2 times.

[0016] Furthermore, the voltage generator proportional to absolute temperature adopts a CMOS structure.

[0017] The beneficial effects of the present invention are:

[0018] (1) The present invention makes the amplitude of the input clock of the voltage generator which is inversely proportional to the absolute temperature appropriate through the design of the clock amplitude converter, thereby widening the normal operating temperature range of the low-voltage bandgap reference voltage circuit without curvature compensation.

[0019] (2) The present invention improves the power supply rejection ratio of the reference voltage ultimately output by the low-voltage bandgap reference voltage circuit through the design of the clock amplitude converter.

[0020] (3) The present invention doubles the power supply voltage by a charge pump, thereby enabling the low-voltage bandgap reference voltage circuit to operate at a low power supply voltage. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a circuit structure principle diagram of the present invention.

[0022] Figure 2 It is a circuit diagram of a clock amplitude converter of the present invention.

[0023] Figure 3 It is a circuit diagram of a voltage generator inversely proportional to absolute temperature of the present invention. DETAILED DESCRIPTION

[0024] The present invention will be described in detail below according to the accompanying drawings and preferred embodiments, and the purpose and effect of the present invention will become more clear. The present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0025] like Figure 1 As shown, the low-voltage bandgap reference voltage circuit without curvature compensation includes: a current source, a low-voltage ring oscillator, a charge pump, a clock amplitude converter, a voltage generator inversely proportional to the absolute temperature, and a voltage generator proportional to the absolute temperature. Most of the existing bandgap reference voltages are based on bipolar junction transistors (hereinafter referred to as BJT) and resistors to generate PTAT voltages, which consumes a large area and power consumption. In order to reduce the power consumption and area of ​​the circuit, the present invention selects a CMOS structure.

[0026] Supply voltage V DD The input current source generates bias current, which is respectively input into the low voltage ring oscillator, the clock amplitude converter, the voltage generator inversely proportional to the absolute temperature, and the voltage generator proportional to the absolute temperature, thereby reducing the power supply voltage V DD The impact of changes on the output frequency of the low voltage ring oscillator, the amplitude of the output clock of the clock amplitude converter, the magnitude of the output voltage of the voltage generator that is inversely proportional to the absolute temperature, and the magnitude of the output voltage of the voltage generator that is proportional to the absolute temperature.

[0027] The power supply voltage V DD The bias current is used as input to the low voltage ring oscillator, and the low voltage ring oscillator outputs the clock signal required by the charge pump.

[0028] The power supply voltage V DD The clock signal obtained from the low-voltage ring oscillator is used as input to the charge pump, which converts the power supply voltage V DD Double the voltage to get a DC voltage of 2×V DD At the same time, the amplitude of the clock signal obtained by the low-voltage ring oscillator is doubled to obtain an output clock amplitude of 2×V DD The DC voltage output by the charge pump is 2×V DD It is used to drive a clock amplitude converter, a voltage generator inversely proportional to absolute temperature, and a voltage generator proportional to absolute temperature, thereby reducing the input power supply voltage required for the entire circuit.

[0029] like Figure 2As shown, the clock amplitude converter includes: BJT, capacitor, inverter. The BJT, capacitor, and two inverters are connected in parallel, and the output clkb of the first inverter is used as the input of the second inverter. The output clock clk_2x obtained by the charge pump, the DC voltage obtained by the charge pump, and the bias current obtained by the current source are used as inputs and input into the clock amplitude converter to obtain an amplitude of V BE The two-phase clock clk and clkb are outputted by the inverter, which are used to control the switch in the voltage generator that is inversely proportional to the absolute temperature. In the clock amplitude converter, the capacitor acts as a temporary power supply to reduce the amplitude drop of the two-phase clock caused by the conduction current of the PMOS tube; therefore, when designing, it is necessary to adjust the size of the capacitor and the size of the MOS tube in the inverter so that the amplitude of the two-phase clock is close to V BE .

[0030] Compared with the amplitude converter mentioned in the existing low-voltage bandgap reference circuit based on switched capacitors, the input of the clock amplitude converter of the present invention is a single clock signal, and no additional multi-phase clock generation circuit is required, that is, the circuit structure is simpler; in addition, the clock amplitude converter of the present invention can generate a clock signal with a suitable amplitude, which can avoid the problem of reference voltage error caused by simultaneous conduction of switches.

[0031] like Figure 3 As shown, the voltage generator inversely proportional to the absolute temperature includes: BJT, 8 switches, and 4 capacitors. The current source is connected to the emitter of the BJT, and the base of the BJT is connected to the collector and grounded; the switch S1 is located between the emitter of the BJT and the left plate of the capacitor C1; the switch S2 is located between the right plate of the capacitor C1 and the left plate of the capacitor C2; the switch S3 is located between the right plate of the capacitor C2 and the left plate of the capacitor C3; the switch S4 is located between the right plate of the capacitor C1 and the ground; the switch S5 is located between the right plate of the capacitor C2 and the ground; the switch S6 is located between the left plate of the capacitor C1 and the output terminal CTAT; the switch S7 is located between the left plate of the capacitor C2 and the output terminal CTAT; the switch S8 is located between the left plate of the capacitor C3 and the output terminal CTAT; the upper plate of the capacitor C4 is connected to the output terminal CTAT, and the lower plate of the capacitor C4 is connected to the ground.

[0032] Since BJT has the characteristic that when a certain current is passed, its base-emitter voltage is inversely proportional to the absolute temperature, the bias current flows through the BJT, resulting in a voltage V with a negative temperature coefficient. BE In order to reduce the overall power consumption of the circuit, the voltage generator inversely proportional to the absolute temperature uses a switched capacitor network to finally obtain a voltage CTAT output inversely proportional to the absolute temperature, whose value is K×V BE (K<1); In order to avoid the limitation of the switch input dynamic range, the switches used in this circuit all adopt CMOS structure.

[0033] When the positive input clock of the voltage generator inversely proportional to the absolute temperature is at a high level, switches S1, S2, and S3 are turned on, and switches S4, S5, S6, S7, and S8 are turned off. At this time, the left plate of capacitor C1 is connected to the emitter of BJT, the current source is connected to the emitter of BJT and the left plate of capacitor C1, capacitors C1, C2, and C3 are connected in series in sequence, the right plate of capacitor C3 is grounded together with the lower plate of capacitor C4, the base and collector of BJT, and the upper plate of capacitor C4 is connected to the output terminal of voltage CTAT. Since C1 = C2 = C3, the voltage drops of capacitors C1, C2, and C3 are all

[0034] When the positive input clock of the voltage generator inversely proportional to the absolute temperature is at a low level, switches S1, S2, and S3 are disconnected, and switches S4, S5, S6, S7, and S8 are turned on. At this time, the current source is connected to the emitter of the BJT, the right plate of capacitor C1, the right plate of capacitor C2, the right plate of capacitor C3, the lower plate of capacitor C4, the base and collector of the BJT are grounded together, and the left plate of capacitor C1, the left plate of capacitor C2, the left plate of capacitor C3, and the upper plate of capacitor C4 are all connected to the output terminal of the voltage CTAT, that is, capacitors C1, C2, and C3 are connected in parallel, and capacitor C4 is charged. After a period of time, the voltage of capacitor C4 is finally stabilized at

[0035] The output clocks clk and clkb of the clock amplitude converter are used as the input clocks of the voltage generator inversely proportional to the absolute temperature to obtain a voltage inversely proportional to the absolute temperature; the voltage inversely proportional to the absolute temperature is used as the input voltage of the voltage generator proportional to the absolute temperature, and the difference voltage between the output voltage of the voltage generator proportional to the absolute temperature and the input voltage has a positive temperature coefficient. Finally, the output of the voltage generator proportional to the absolute temperature is the reference voltage.

[0036] If the amplitude of the input clock signal of the switched capacitor network in the voltage generator inversely proportional to absolute temperature is constant, the error of the output voltage caused by charge injection and clock feedthrough of the switched capacitor network is also constant; however, the amplitude of the output clock of the low-voltage ring oscillator and the charge pump is related to the power supply voltage. In order to improve the power supply rejection ratio of the final output reference voltage, it is necessary to introduce a clock amplitude converter to generate a clock signal whose amplitude does not change with the power supply voltage. In addition, considering the input range of the voltage generator inversely proportional to absolute temperature and the characteristics of the CMOS switch, if the amplitude of the input clock of the voltage generator inversely proportional to absolute temperature is too small, it may cause the PMOS tube in the CMOS switch to be continuously turned off and the NMOS tube to be turned on, thereby making the circuit unable to work normally; if the amplitude of the input clock of the voltage generator inversely proportional to absolute temperature is too large, it may cause the NMOS tube in the switch to be turned on at the rising edge or falling edge of the clock at the same time, that is, S1~S8 will be turned on at a fixed time at the same time, thereby causing a large output error. Assuming that the amplitude of the clock signal controlling the switch in the voltage generator inversely proportional to the absolute temperature is constant, since the threshold voltage of the MOS tube decreases with the increase of temperature, the higher the temperature, the greater the conduction current when the MOS tubes are turned on at the same time, so the error of the output voltage increases with the increase of temperature; from this perspective, selecting an input clock with a suitable amplitude for the voltage generator inversely proportional to the absolute temperature can broaden the operating temperature range of the circuit. It is deduced that in the voltage generator inversely proportional to the absolute temperature, the amplitude V of the positive input clock signal controlling the switch h Should be limited to to avoid the output errors caused by the above two situations, where V thn is the threshold voltage of the NMOS in the switch, V thp is the threshold voltage of the PMOS in the switch. Since the base-emitter voltage V BE satisfy Therefore, the clock amplitude converter used in the present invention generates V h =V BE The clock signal serves as the input clock of a voltage generator which is inversely proportional to the absolute temperature.

[0037] Those skilled in the art can understand that the above are only preferred examples of the invention and are not intended to limit the invention. Although the invention is described in detail with reference to the above examples, those skilled in the art can still modify the technical solutions recorded in the above examples or replace some of the technical features therein with equivalents. Any modification, equivalent replacement, etc. made within the spirit and principle of the invention shall be included in the protection scope of the invention.

Claims

1. A low voltage bandgap reference voltage circuit without curvature compensation, characterized in that: include: Current sources, low voltage ring oscillators, charge pumps, clock amplitude converters, voltage generators inversely proportional to absolute temperature, voltage generators directly proportional to absolute temperature; The power supply voltage is input into the current source to generate a bias current; the input of the low-voltage ring oscillator is the power supply voltage and the bias current, and the output is a clock signal; the input of the charge pump is the power supply voltage and the clock signal output by the low-voltage ring oscillator, the charge pump doubles the input power supply voltage and the amplitude of the input clock signal, and the output of the charge pump is a DC voltage and a clock signal; the input of the clock amplitude converter is the bias current, the output clock of the charge pump and the DC voltage, and the output is a two-phase clock whose amplitude does not change with the power supply voltage; the input of the voltage generator inversely proportional to the absolute temperature is the two-phase clock, the bias current, and the DC voltage output by the charge pump, and the output is a voltage inversely proportional to the absolute temperature; the input of the voltage generator proportional to the absolute temperature is the voltage inversely proportional to the absolute temperature, the bias current, and the DC voltage output by the charge pump, and the output is a reference voltage; The clock amplitude converter includes: a bipolar junction transistor, a capacitor, and two inverters arranged in parallel. The bias current generated by the current source is input into the clock amplitude converter, and the output of the first inverter is used as the input of the second inverter. The outputs of the two inverters are two-phase clocks output by the clock amplitude converter.

2. The low-voltage bandgap reference voltage circuit without curvature compensation according to claim 1, characterized in that: The voltage generator inversely proportional to the absolute temperature comprises: a bipolar junction transistor, three capacitors of the same specification, a capacitor at the output end, and eight switches, all of which adopt a CMOS structure; the current source is connected to the emitter of the bipolar junction transistor, the base of the bipolar junction transistor is connected to the collector and grounded; the switch S1 is located between the emitter of the bipolar junction transistor and the left plate of the capacitor C1; the switch S2 is located between the right plate of the capacitor C1 and the left plate of the capacitor C2; the switch S3 is located between the right plate of the capacitor C1 and the left plate of the capacitor C2; the switch S4 is located between the right plate of the capacitor C1 and the left plate of the capacitor C2; the switch S5 is located between the right plate of the capacitor C1 and the left plate of the capacitor C2; the switch S6 is located between the right plate of the capacitor C1 and the left plate of the capacitor C2; the switch S7 is located between the right plate of the capacitor C1 and the left plate of the capacitor C2; the switch S8 is located between the right plate of the capacitor C1 and the left plate of the capacitor C2; the switch S9 is located between the right plate of the capacitor C1 and the left plate of the capacitor C2; the switch S10 is located between the right plate of the capacitor C1 and the left plate of the capacitor C2; the switch S11 is located between the right plate of the capacitor C1 and the left plate of the capacitor C2; the switch S12 is located between the right plate of the capacitor C1 and the left plate of the capacitor C2; the switch S13 is located between the right plate of the capacitor C1 and the left plate of the capacitor C2; the switch S14 is located between the right plate of the capacitor C1 and the left plate of the capacitor C2; the switch S15 is located between the right plate of the capacitor C1 and the left plate of the capacitor C2; the switch S16 is located between the right plate of the capacitor C1 and the left plate of the capacitor C2; the switch S17 is located between the right plate of the capacitor C1 and the left plate of the capacitor The switch S4 is located between the right plate of the capacitor C1 and the ground; the switch S5 is located between the right plate of the capacitor C2 and the ground; the switch S6 is located between the left plate of the capacitor C1 and the output terminal CTAT; the switch S7 is located between the left plate of the capacitor C2 and the output terminal CTAT; the switch S8 is located between the left plate of the capacitor C3 and the output terminal CTAT; the upper plate of the capacitor C4 is connected to the output terminal CTAT, and the lower plate of the capacitor C4 is connected to the ground.

3. The low-voltage bandgap reference voltage circuit without curvature compensation according to claim 2, characterized in that: When the positive input clock of the voltage generator inversely proportional to the absolute temperature is at a high level, switches S1, S2, and S3 are turned on, and switches S4, S5, S6, S7, and S8 are turned off. At this time, capacitors C1, C2, and C3 are connected in series in sequence and in parallel with the bipolar junction transistor. Since C1 = C2 = C3, the voltage drops of capacitors C1, C2, and C3 are all V BE It is the voltage with negative temperature coefficient obtained after bias current flows through the bipolar junction transistor; When the positive input clock of the voltage generator inversely proportional to the absolute temperature is at a low level, switches S1, S2, and S3 are disconnected, and switches S4, S5, S6, S7, and S8 are turned on. At this time, capacitors C1, C2, and C3 are connected in parallel, and capacitors C1, C2, and C3 charge capacitor C4. The voltage of capacitor C4 finally stabilizes at 4. The low-voltage bandgap reference voltage circuit without curvature compensation according to claim 2, characterized in that: In a voltage generator that is inversely proportional to absolute temperature, the amplitude of the positive input clock V h Should meet: Where V BE V is the voltage with a negative temperature coefficient obtained after the bias current flows through the bipolar junction transistor. thn is the threshold voltage of the NMOS in the switch, V thp is the threshold voltage of the PMOS in the switch.

5. The low-voltage bandgap reference voltage circuit without curvature compensation according to claim 1, characterized in that: The charge pump doubles the input power supply voltage by 2 times and doubles the amplitude of the input clock signal by 2 times.

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