CN103513689A - Lower-power-consumption reference source circuit - Google Patents

Abstract

The invention discloses a lower-power-consumption reference source circuit. The lower-power-consumption reference source circuit comprises a starting circuit unit, a current generation circuit unit and an output load circuit unit, wherein the starting circuit unit, the current generation circuit unit and the output load circuit unit are connected in sequence, the starting circuit unit is used for providing starting voltage, and preventing operation in a zero state area, the current generation circuit unit is used for generating microcurrent for the output load circuit unit, and reducing power consumption of the lower-power-consumption reference source circuit, and the output load circuit unit is used for achieving output of a zero-temperature coefficient and low-output voltage. The lower-power-consumption reference source circuit has the advantages of being low in power consumption, low in temperature coefficient, large in range of operating voltage and small in area.

Description

A low power consumption reference source circuit

technical field

The invention relates to a reference source circuit with low power consumption, low temperature coefficient, wide working range and small area, more specifically, a reference source circuit with low power consumption.

Background technique

Reference source circuit modules are widely used in analog and mixed circuits, such as A/D, D/A converters, voltage tuners, voltmeters, ammeter test instruments and bias circuits. The output reference signal is stable and has nothing to do with power supply voltage, temperature and process changes. In the SOC (system on chip) chip, the reference source circuit is an essential part. Many modules of the chip need a reference source to provide stable voltage or current, so the design of the reference source becomes the key to the entire chip design.

The following performance indicators are mainly considered in the design of the reference source circuit: temperature coefficient, operating voltage range, power supply rejection ratio and power consumption. The lower the temperature coefficient is, the less the output voltage of the reference source circuit is affected by the temperature, the more stable the voltage is. A larger operating range can make it easier for the reference source circuit to reach the target output voltage value. In order to meet the current requirements for low power consumption of power management chips, the design of the reference source circuit should minimize its operating current, thereby reducing its power consumption and making the battery's working life longer.

For the traditional reference source circuit, two current modules with different temperature coefficients are usually used to realize the voltage output with zero temperature coefficient. The designer needs to design a positive temperature coefficient current (the current increases with the increase of temperature) and a negative temperature coefficient current (the current decreases with the decrease of temperature) and then superimpose these two current modules to reduce the influence of temperature on the current , the current through the resistor can finally get a voltage output with a low temperature coefficient.

Figure 1 is a traditional bandgap reference circuit structure. The negative feedback formed by the operational amplifier OP makes the node voltage VA=VB, so that the currents flowing through M1 and M2 are equal, that is, I1=I2=I, and the voltage drop on the resistor R1 is equal to the base-emitter voltage of Q1 and Q2 Difference, the value is VBE=VTlnN, VT represents the voltage value related to temperature changes, and N is the ratio of the emission area of Q1 and Q2. In this circuit configuration, the reference output voltage is the sum of the base-emitter voltage VBE3 of bipolar transistor Q3 and the voltage drop across resistor R2. The reference output voltage is the sum of the base-emitter voltage VBE3 of the bipolar transistor Q3 and the voltage drop across the resistor R2, so the expression for VREF is as follows:

               （1）

(1)

The second term in the formula is proportional to the absolute temperature and is used to compensate the negative temperature coefficient of VBE3. By choosing an appropriate ratio of R1 and R2, the temperature coefficient of the reference voltage can reach zero at a certain temperature, and the reference voltage changes little with temperature around this value.

But there are certain deficiencies in this structure. First of all, the temperature coefficient that this structure can reach is relatively high, generally between 20-100ppm/°C. Secondly, the output voltage of this circuit is about 1.2 volts, which is not suitable for low-voltage occasions. The circuit uses triodes and resistors, and the area of the circuit is relatively large. Again, the start-up speed of this kind of circuit is slow, and the reference voltage of the bandgap reference voltage source will not be turned off even when it is too high, so the self-protection of the circuit cannot be realized. Moreover, the power supply rejection ratio of the circuit is usually not ideal, especially in an environment with relatively harsh power supply noise, the reference output voltage will be greatly disturbed by noise.

Contents of the invention

In view of the above problems, the object of the present invention is to propose a CMOS low power consumption reference source circuit with low power consumption, wide working range, small area and low temperature coefficient by utilizing the operating characteristics of CMOS transistors in the subthreshold region.

In order to achieve the above object, the technical solution of the present invention is:

A low-power reference source circuit, comprising sequentially connecting a starting circuit unit, a current generating circuit unit and an output load circuit unit;

The starting circuit unit is used to provide a starting voltage to avoid working in a zero state area;

The current generation circuit unit is used to generate a micro current for the output load circuit unit, and at the same time reduce the power consumption of the low power consumption reference source circuit;

The output load circuit unit is used to realize output zero temperature coefficient and low output voltage.

The start-up circuit unit provides a start-up signal for the reference source circuit and other circuit units when the circuit is started, so that the reference source circuit and other circuit units can get rid of working at the "degenerate point", and can enable the start-up circuit after the reference source circuit works normally. Shutdown for low power consumption.

The above-mentioned output load circuit unit is an output mechanism composed of two MOS transistors with different gate threshold voltages.

Preferably, the start-up circuit unit includes MOS transistors MS0, MS1, MS2, MS3 and MC; the MS1 and MS2 are connected with a current mirror pair, the source of MS1 and the source of MS2 are grounded, and the drain of MS2 is connected to MS3 The source of MS1 is connected to the gate of MS0, the gate of MS0 is connected to the gate of MC, the drain of MS0 is connected to the gate of MS3, the drain of MC and the drain of MS3 are connected to the power supply , the drain of MC is connected to the source, the drain of MS0 and the source of MS0 are respectively the first and second start signal output terminals, which provide the start signal to the current generation circuit unit; the MS3 and MC are PMOS transistors.

The drain of the MC is connected to the power supply, and the grid, drain and source of the MC are connected together, which acts as a capacitor in the start-up circuit to reduce the area of the circuit structure.

Preferably, the current generation circuit unit includes MOS transistors M1, M2, M3, PM1 and PM2, and the MOS transistors PM1 and PM2 are connected in a current mirror structure so that the currents of the two branches are equal, and the drain of PM1 is connected to the drain of PM2 Connected to the power supply, the gate of PM1, the gate of PM2 are connected to the source of PM2, the source of PM2 is the current output terminal, and connected to the first start signal output terminal of the starting circuit unit; the gate of M1, the drain of M2 The pole is connected to the source of M3, the source of PM1, the gate of M3, the drain of M3 are connected to the gate of M2, and the gate of M2 is connected to the second start signal output terminal of the start circuit unit. The current generation circuit unit uses a group of cascaded MOSs to determine the output micro-current according to the voltage relationship of each MOS. According to the voltage-current relationship of the connection points of M1, M2 and M3, the expression of the current can be obtained. The current is related to the width-to-length ratio of M1, M2 and M3. By adjusting the width-to-length ratio, a lower output current can be obtained.

The current generation circuit unit is connected with the starting circuit unit to ensure that the circuit can be started normally, and at the same time, when the circuit works normally, the starting circuit unit is disconnected as a feedback signal, thereby reducing power consumption. Provide start-up signals for the reference source, chip and other circuit modules at any time, so that the reference source circuit and other circuit units can get rid of working at the "degenerate point", and can turn off the start-up circuit after the reference source circuit works normally to achieve low power consumption .

Preferably, the output load circuit unit includes MOS transistors M4, M5 and PM3, the gate of PM3 is used as the input end of the output load circuit unit, and is connected to the first start signal output end of the start circuit unit, and the drain of PM3 is connected to Power supply, PM3 and PM2 in the current generation circuit unit form a current mirror, mirroring the current generated by the current generation circuit unit to the output load circuit unit; the drain of M4, the gate of M4 and the gate of M5 are connected, and the source of M4 The pole is connected to the drain of M5, the source of M5 is grounded, M4 and M5 are cascaded as an output load, and the connection point between the source of M4 and the drain of M5 is the output node VREF.

The entire low-power reference source circuit only uses MOS transistors instead of capacitors and resistors, thereby reducing the area of the circuit, and the circuit works in the sub-threshold region to generate less power consumption.

Preferably, M4 in the output load circuit unit is an nmvt3.3 tube with a lower gate threshold voltage, M5 is an n3.3 tube with a higher gate threshold voltage, and the gate threshold of M5 is greater than that of M4 , the output voltage value is about the difference between the two. Since the nmvt3.3 tube has a different gate threshold voltage and temperature coefficient from other tubes, it achieves zero temperature coefficient.

Preferably, the power supply voltage of the MOS transistors in the low-power reference source circuit is 3.3V, so that the low-power reference source circuit has a wider working range.

Compared with the prior art, the beneficial effect of the present invention lies in that the present invention has the characteristics of simple structure, small realization area, low temperature coefficient, low power consumption, low output voltage and wide working range.

Description of drawings

Figure 1 is a connection diagram of a traditional reference source circuit.

Fig. 2 is a connection diagram of the startup circuit of the present invention.

Fig. 3 is a connection diagram of the output load circuit of the present invention.

Fig. 4 is a connection diagram of the current generating circuit of the present invention.

Fig. 5 is a connection diagram of the reference source circuit of the present invention.

Detailed ways

The present invention will be further described below in conjunction with the accompanying drawings, but the embodiments of the present invention are not limited thereto.

The present invention utilizes the operating characteristics of CMOS transistors in the sub-threshold region to design a reference source circuit with low power consumption, low temperature coefficient and small area. By using CMOS with different gate thresholds to realize stable voltage output, stable voltage output with low temperature coefficient is realized. The voltage and current characteristics of a CMOS transistor working in the subthreshold region are shown in the following expression:

           （2）

(2)

where V _TH is the gate threshold voltage with a positive temperature coefficient and V _T is the thermal voltage ( V _T =k _BT /q ) with a negative temperature coefficient. K is the width-to-length ratio of the CMOS tube, ID is the drain current, u is the carrier mobility, and C _OX is the capacitance _of the gate oxide layer.

As shown in Fig. 5, a low power consumption reference source circuit includes sequentially connecting a starting circuit unit 1, a current generating circuit unit 2 and an output load circuit unit 3;

The starting circuit unit 1 is used to provide a starting voltage, avoid working in a zero state area, and ensure the normal operation of the circuit;

The current generation circuit unit 2 is used to generate a micro current for the output load circuit unit, while reducing the power consumption of the low power consumption reference source circuit;

The output load circuit unit 3 utilizes CMOS transistors nmvt with different gate thresholds to realize output with zero temperature coefficient and low output voltage.

In this embodiment, all the CMOS transistors in the low-power reference source circuit are 3.3V, and the 3.3V CMOS transistors have a wider working range, thereby increasing the working range of the reference source circuit structure. The reference source circuit structure only uses CMOS components, and does not use capacitors, resistors and triodes, which can reduce the impact of its offset on the circuit, and can effectively reduce the implementation area of the circuit.

As shown in Figure 2, the starting circuit unit 1 includes MOS transistors MS0, MS1, MS2, MS3 and MC; the MS1 and MS2 are connected with a current mirror pair, the source of MS1 and the source of MS2 are grounded, and the drain of MS2 and The source of MS3 is connected, the drain of MS1 is connected to the gate of MS0, the gate of MS0 is connected to the gate of MC, the drain of MS0 is connected to the gate of MS3, the drain of MC and the drain of MS3 are connected to the power supply connection, the MC drain is connected to the source, the drain of MS0 and the source of MS0 are respectively the first and second start signal output terminals, which provide the start signal to the current generation circuit unit; the MS3 and MC are PMOS transistors. The drain of the MC is connected to the power supply, and the grid, drain and source of the MC are connected together, which acts as a capacitor in the start-up circuit to reduce the area of the circuit structure.

As shown in Figure 3, the described output load circuit unit includes MOS transistors M4, M5 and PM3, the gate of PM3 is used as the input end of the output load circuit unit, and is connected with the first start signal output end of the start circuit unit, and the PM3 The drain is connected to the power supply, PM3 and PM2 in the current generating circuit unit form a current mirror, mirroring the current generated by the current generating circuit unit to the output load circuit unit; the drain of M4, the gate of M4 and the gate of M5 are connected, The source of M4 is connected to the drain of M5, the source of M5 is grounded, M4 and M5 are cascaded as an output load, and the connection point between the source of M4 and the drain of M5 is the output node V _ref . The output voltage expression is as follows:

                   （3）

(3)

The MOS tube M4 uses nmvt3.3 tube (Medium V _TH CMOS), and its gate threshold voltage V _TH4 =487mV is lower than that of other CMOS ( V _TH5 =695mV). At the same time, the nmvt3.3 tube has a temperature coefficient different from that of the n3.3 tube, and the difference between the two can more effectively reduce the temperature coefficient of the reference source circuit structure. According to the voltage and current characteristics of the MOS tube working in the sub-threshold region, the expression of the output voltage can be further obtained:

  （4）

(4)

It can be seen from the above formula that the influence of T on the output voltage can be eliminated by adjusting the width-to-length ratio K of _M4 and _M5 , thereby achieving zero temperature coefficient.

As shown in Figure 4, described electric current generating circuit unit comprises MOS tube M1, M2, M3, PM1 and PM2, and MOS tube PM1 and PM2 are connected with current mirror structure to make the current of two branches equal, the drain of PM1 and PM2 The drain of PM1 is connected to the power supply, the grid of PM1, the grid of PM2 are connected with the source of PM2, and the source of PM2 generates the current output end, and is connected with the first start signal output end of the startup circuit unit; the grid of M1, The drain of M2 is connected to the source of M3, the gate of M2 is connected to the second starting signal output terminal of the starting circuit unit, the source of PM1, the gate of M3, the drain of M3 are connected to the gate of M2, and The voltage relationship at the connection point is shown in formula (4):

(5)

According to the voltage and current characteristics of the CMOS tube working at the sub-threshold, as shown in formula (2), the expression of the current I ₁ of the circuit can be further generated by the circuit:

             （6）

(6)

It can be seen from the above formula that by adjusting the width-to-length ratio K of M1, M2 and M3, a small working current can be obtained. .

The current generating circuit unit is connected with the starting circuit unit to ensure that the circuit can start normally, and at the same time, when the circuit works normally, the starting circuit unit is disconnected as a feedback signal, thereby reducing power consumption, and the first starting signal of the starting circuit unit is output The terminal is connected with the output load circuit unit, and the MOS transistors PM3 and PM2 form a current mirror, through which the output load circuit of the current mirror can obtain a current I3 proportional to I1, and the ratio is determined by the width-to-length ratio of PM2 and PM3.

The embodiments of the present invention described above are not intended to limit the protection scope of the present invention. Any modifications, equivalent replacements and improvements made within the spirit and principle of the present invention shall be included in the protection scope of the claims of the present invention.

Claims (6)

1. A low-power consumption reference source circuit, characterized in that it comprises sequentially connecting a starting circuit unit, a current generating circuit unit and an output load circuit unit; The starting circuit unit is used to provide a starting voltage to avoid working in a zero state area; The current generation circuit unit is used to generate a micro current for the output load circuit unit, and at the same time reduce the power consumption of the low power consumption reference source circuit; The output load circuit unit is used to realize output zero temperature coefficient and low output voltage. 2. The low-power reference source circuit according to claim 1, wherein the start-up circuit unit includes MOS transistors MS0, MS1, MS2, MS3 and MC; the MS1 and MS2 are connected with a current mirror pair, The source of MS1 and the source of MS2 are grounded, the drain of MS2 is connected to the source of MS3, the drain of MS1 is connected to the gate of MS0, the gate of MS0 is connected to the gate of MC, the drain of MS0 is connected to the gate of MS3 The gates are connected, the drain of MC and the drain of MS3 are connected to the power supply, the drain of MC is connected to the source, the drain of MS0 and the source of MS0 are respectively the first and second start signal output terminals, and the current generation The circuit unit provides a starting signal; the MS3 and MC are PMOS transistors. 3. The low-power reference source circuit according to claim 1, wherein the current generation circuit unit includes MOS transistors M1, M2, M3, PM1 and PM2, and the MOS transistors PM1 and PM2 are connected in a current mirror structure , the drain of PM1 and the drain of PM2 are connected to the power supply, the grid of PM1, the grid of PM2 are connected with the source of PM2, the source of PM2 is the current output end, and is connected with the first start signal output end of the startup circuit unit Connection; the gate of M1, the drain of M2 are connected to the source of M3, the source of PM1, the gate of M3, the drain of M3 are connected to the gate of M2, the gate of M2 is connected to the second Start signal output connection. 4. The low-power reference source circuit according to claim 1, wherein the output load circuit unit includes MOS transistors M4, M5 and PM3, and the gate of PM3 is used as the input terminal of the output load circuit unit, and The first starting signal output end of the starting circuit unit is connected, the drain of PM3 is connected to the power supply, the drain of M4, the gate of M4 are connected to the gate of M5, the source of M4 is connected to the drain of M5, and the source of M5 Grounded, M4 and M5 are cascaded as an output load, and the connection point of the source of M4 and the drain of M5 is the output node VREF. 5. The low-power reference source circuit according to claim 1, wherein M4 in the output load circuit unit is an nmvt3.3 tube, M5 is an n3.3 tube, and the gate threshold of M5 is greater than the gate of M4 threshold. 6. The circuit of the low-power reference source according to claim 1, wherein the power supply voltages of the MOS tubes in the low-power reference source circuit are all 3.3V.

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