Band-gap reference circuit with undervoltage protection

Abstract

The invention belongs to the field of integrated circuits, and particularly relates to a band-gap reference circuit with under-voltage protection, which comprises a band-gap reference generating circuit and a reference under-voltage protection circuit, and is characterized in that the band-gap reference generating circuit is used for generating an accurate and stable reference voltage; and when the output voltage of the band-gap reference generation circuit is smaller than a set voltage value, the reference under-voltage protection circuit is used for turning off a post-stage circuit to carry out under-voltage protection. The circuit provided by the invention not only can generate an accurate band-gap reference voltage, but also can realize under-voltage protection before the reference is established.

Description

Technical Field

[0001] The invention belongs to the field of integrated circuits, and in particular relates to a bandgap reference circuit with undervoltage protection. Background Art

[0002] Bandgap reference circuits and undervoltage protection circuits are widely used in integrated circuits, especially in power management chips, to provide an accurate reference voltage and generate an indication signal in the case of undervoltage, to achieve voltage monitoring, and to improve the yield, accuracy and reliability of the overall circuit.

[0003] like Figure 1 It is a traditional bandgap reference circuit, including PMOS tubes M1 and M2, NPN transistors Q1~Q6, resistors R1~R3, and capacitor C1. Q3 and Q4 are reference cores for generating a bandgap reference voltage V OUT , Q5 and Q6 provide clamping, PMOS tubes M2 and M1 form a current mirror, and the emitter area ratio of Q3 and Q4 is 1:n:

[0004]

[0005] Among them, V BE,Q3 for Figure 1 The BE junction voltage of NPN transistor Q3, R 1 , R 3 for Figure 1 The resistance of resistors R1 and R3, V T is the voltage equivalent of temperature.

[0006] The traditional bandgap reference circuit can only generate a reference voltage and has no undervoltage indication function.

[0007] like Figure 2 It is a traditional undervoltage protection circuit, which is essentially a voltage comparator, including PMOS tubes M1~M4 and NMOS tubes M5~M7. The gate of M3 is the reference voltage VREF of the comparator, which is generally the reference voltage of the system circuit, the gate of M4 is the voltage to be compared VM, and UVLO is the undervoltage protection output. When the VM voltage is lower than the reference voltage, UVLO outputs a low level. When the VM terminal voltage rises to be greater than the reference voltage, UVLO outputs a high level, indicating that the circuit is working normally. The traditional undervoltage protection circuit requires an additional reference voltage VREF and needs to provide a higher power supply voltage VIN. It is not suitable for undervoltage protection before the reference is established or under low power supply voltage conditions. Summary of the invention

[0008] In order to overcome the shortcomings of the above-mentioned bandgap reference circuit, the present invention proposes a novel bandgap reference circuit with undervoltage protection, including a bandgap reference generating circuit and a reference undervoltage protection circuit. The bandgap reference generating circuit is used to generate an accurate and stable reference voltage. When the output voltage of the bandgap reference generating circuit is less than the set voltage value, the subsequent circuit is shut down by the reference undervoltage protection circuit to perform undervoltage protection.

[0009] The beneficial effects of the present invention are:

[0010] (1) The circuit of the present invention can not only generate an accurate bandgap reference voltage, but also implement undervoltage protection before the reference is established;

[0011] (2) The undervoltage protection circuit of the present invention does not require an additional reference voltage and a complex comparison circuit;

[0012] (3) The bandgap reference undervoltage protection circuit of the present invention can meet the low voltage working requirements. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 A conventional bandgap reference circuit;

[0014] Figure 2 A conventional undervoltage protection circuit;

[0015] Figure 3 The bandgap reference generating circuit of the present invention;

[0016] Figure 4 The bandgap reference undervoltage protection circuit of the present invention;

[0017] exist Figures 3-4 In the figure, R1 is the first resistor; R2 is the second resistor; R3 is the third resistor; R5 is the fifth resistor; R6 is the sixth resistor; R7 is the seventh resistor; R8 is the eighth resistor; R9 is the ninth resistor;

[0018] M1, the first MOS tube; M2, the second MOS tube; M3, the third MOS tube; M4, the fourth MOS tube; M5, the fifth MOS tube; M6, the sixth MOS tube; M7, the seventh MOS tube; M8, the eighth MOS tube; M9, the ninth MOS tube; M10, the tenth MOS tube;

[0019] Q1, a first transistor; Q2, a second transistor; Q3, a third transistor; Q4, a fourth transistor; Q5, a fifth transistor; Q6, a sixth transistor; Q7, a seventh transistor;

[0020] I1, first inverter; I2, second inverter;

[0021] VIN, power supply terminal; EN1, first enable terminal; EN2, second enable terminal; EN3, third enable terminal; VBG, bandgap reference voltage output terminal; UVLO, reference undervoltage protection output terminal; GND, ground terminal. DETAILED DESCRIPTION

[0022] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0023] The present invention proposes a novel bandgap reference circuit with undervoltage protection, comprising a bandgap reference generating circuit and a reference undervoltage protection circuit. The bandgap reference generating circuit is used to generate an accurate and stable reference voltage. When the output voltage of the bandgap reference generating circuit is less than a set voltage value, the reference undervoltage protection circuit shuts down the subsequent circuit to perform undervoltage protection.

[0024] The present invention provides a bandgap reference circuit with undervoltage protection, comprising a bandgap reference generating circuit and a reference undervoltage protection circuit, wherein the bandgap reference generating circuit comprises a first resistor R1 to a third resistor R3, a first MOS tube M1 to a fourth MOS tube M4, a seventh MOS tube M7, an eighth MOS tube M8, a first transistor Q1 to a fourth transistor Q4, a power supply voltage terminal VIN, a first enable signal EN1, a second enable signal EN2, a bandgap reference output voltage terminal VBG, a ground terminal GND, the first MOS tube M1 to the fourth MOS tube M4 are P-type MOS tubes, the seventh MOS tube M7 and the eighth MOS tube M8 are N-type MOS tubes, the first transistor Q1 to the fourth transistor Q4 are NPN-type transistors, such as Figure 3 ,in:

[0025] The sources of the first MOS tube M1 to the fourth MOS tube M4 are connected to the power supply terminal VIN, the gates of the first MOS tube M1, the second MOS tube M2 and the fourth MOS tube M4 are connected to the first enable signal EN1, and the gate of the third MOS tube M3 is connected to the second enable signal EN2;

[0026] The drain of the first MOS tube M1, the drain of the seventh MOS tube M7 and the base of the first transistor Q1 are connected, and the gate of the seventh MOS tube M7, the drain of the second MOS tube M2 and the collector of the second transistor Q2 are connected;

[0027] The collector of the first transistor Q1 is connected to the bandgap reference output voltage terminal VBG, and is connected to the upper end of the first resistor R1 and the drain of the third MOS transistor M3;

[0028] The base of the second transistor Q2, the lower end of the second resistor R2 and the upper end of the third resistor R3 are connected, and the emitter of the second transistor Q2 is connected to the drain of the eighth MOS transistor M8 and the emitter of the fourth transistor Q4;

[0029] The lower end of the first resistor R1, the upper end of the second resistor R2 and the base of the fourth transistor Q4 are connected, and the lower end of the third resistor R3 is connected to the base and collector of the third transistor Q3;

[0030] The collector of the fourth transistor Q4, the drain of the fourth MOS tube M4 and the gate of the eighth MOS tube M8 are connected, and the sources of the seventh MOS tube M7 and the eighth MOS tube M8, the emitters of the first transistor Q1 and the third transistor Q3 are connected to the ground terminal GND.

[0031] The reference undervoltage protection circuit includes a fifth resistor R5 to a ninth resistor R9, a fifth MOS tube M5, a sixth MOS tube M6, a ninth MOS tube M9, and a tenth MOS tube M10, a fifth transistor Q5 to a seventh transistor Q7, a first inverter I1, a second inverter I2, a power supply voltage terminal VIN, a third enable signal EN3, a bandgap reference voltage terminal VBG, an undervoltage protection output terminal UVLO, and a ground terminal GND. The fifth MOS tube M5, the sixth MOS tube M6, the ninth MOS tube M9, and the tenth MOS tube M10 are P-type MOS tubes, and the fifth transistor Q5 to the seventh transistor Q7 are NPN-type transistors. Figure 4 ,in:

[0032] The source electrodes of the fifth MOS transistor M5 and the sixth MOS transistor M6 are connected to the power supply terminal VIN, and the gate electrodes of the fifth MOS transistor M5 and the sixth MOS transistor M6 are connected to the third enable signal EN3;

[0033] The bandgap reference voltage terminal VBG is connected to the drain of the fifth MOS tube M5, the source of the ninth MOS tube M9 and the tenth MOS tube M10, and the upper ends of the fifth resistor R5 and the seventh resistor R7;

[0034] The drain of the ninth MOS transistor M9 is connected to the lower end of the fifth resistor R5 and the upper end of the sixth resistor R6. The lower end of the sixth resistor R6 is connected to the collector and base of the fifth transistor Q5 and the base of the sixth transistor Q6.

[0035] The lower end of the seventh resistor R7 is connected to the drain of the tenth MOS transistor M10 and the upper end of the eighth resistor R8, and the lower end of the eighth resistor R8 is connected to the collector of the sixth transistor Q6 and the base of the seventh transistor Q7;

[0036] The emitter of the sixth transistor Q6 is connected to the upper end of the ninth resistor R9, and the collector of the seventh transistor Q7 is connected to the drain of the sixth MOS tube M6 and serves as the output end UVLO of the under-voltage protection;

[0037] The output terminal UVLO of the undervoltage protection is connected to the gates of the ninth MOS tube M9 and the tenth MOS tube M10 through two-stage inverters, namely, the second inverter I2 and the first inverter I1;

[0038] The emitter of the fifth transistor Q5, the emitter of the seventh transistor Q7, and the lower end of the ninth resistor R9 are connected to the ground terminal GND.

[0039] The present invention is a bandgap reference circuit with undervoltage protection function. The circuit is divided into two parts. The first part is as follows: Figure 3 The second part of the bandgap reference generation circuit shown in FIG. Figure 4 The undervoltage protection circuit of the bandgap reference shown in the figure. In the first part, the first enable terminal EN1 and the second enable terminal EN2 signals are at low level, the current source branch where the first MOS tube M1, the second MOS tube M2, the third MOS tube M3 and the fourth MOS tube M4 are located is turned on, the first resistor R1 to the third resistor R3, the second transistor Q2 to the fourth transistor Q4 form a bandgap core structure, the ratio of the emitter area of ​​the fourth transistor Q4 to the second transistor Q2 is 1:4, and the ratio of the emitter current is 2:1, and the bandgap reference voltage VBG can be expressed as:

[0040]

[0041] Among them, V BE,Q3 is the BE junction voltage of the third transistor Q3, V T Indicates the voltage equivalent of temperature. At room temperature, V T =26mV; R 1 , R 2 , R 3 are the resistance values ​​of the first resistor R1, the second resistor R2, and the third resistor R3 respectively;

[0042] The collector of the fourth transistor Q4 is connected to the gate of the eighth MOS tube M8 to form a feedback loop, adjust the static operating points of the fourth transistor Q4 and the second transistor Q2, and ensure the normal operation of the reference. The seventh MOS tube M7, the first transistor Q1 and the reference main circuit form a feedback loop to improve the PSRR performance of the reference. When the voltage of the bandgap reference voltage output terminal VBG decreases, the base voltage of the second transistor Q2 decreases, resulting in an increase in the collector voltage of the second transistor Q2, that is, the gate voltage of the seventh MOS tube M7 increases, resulting in a decrease in the drain voltage of the seventh MOS tube M7, that is, the base voltage of the first transistor Q1 decreases, and the collector voltage of the first transistor Q1 will increase, that is, the VBG voltage increases; when the voltage of the bandgap reference voltage output terminal VBG increases, the adjustment process is opposite to it, thereby playing a role in stabilizing the loop.

[0043] In the second part, the third enable signal EN3 is at a low level, the current source branch where the fifth MOS tube M5 and the sixth MOS tube M6 are located is turned on, the fifth resistor R5, the sixth resistor R6, the seventh resistor R7, and the eighth resistor R8 are equal in size, ensuring that the emitter currents of the fifth transistor Q5 and the sixth transistor Q6 are equal, the seventh transistor Q7 and the sixth MOS tube M6 form a current comparator structure, and the ratio of the emitter area of ​​the fifth transistor Q5 to that of the sixth transistor Q6 is 1:8. The voltage at the bandgap reference voltage output terminal VBG is greater than (Wherein, V BE,Q5 represents the BE junction voltage of the fifth transistor, R 5 , R 6 , R 9 Representing the resistance values ​​of the fifth resistor R5, the sixth resistor R6, and the ninth resistor R9 respectively), the current of the seventh transistor Q7 is relatively large, its drain voltage is pulled down, the undervoltage protection output signal UVLO of the bandgap reference voltage output terminal VBG is low, and the overall circuit works normally. Voltage hysteresis is introduced into the circuit through the fifth resistor R5, the seventh resistor R7, the ninth MOS tube M9, and the tenth MOS tube M10. When the voltage of the bandgap reference voltage output terminal VBG decreases from high, UVLO is initially at a low level, the ninth MOS tube M9 and the tenth MOS tube M10 are turned on, and the fifth resistor R5 and the seventh resistor R7 are short-circuited. Therefore, when the voltage of the bandgap reference voltage output terminal VBG is less than When the UVLO is on, it will output a high level and shut down the subsequent circuit module, thus playing the role of undervoltage protection.

[0044] The bandgap reference circuit with undervoltage protection of the present invention is particularly suitable for use in power supply chips for undervoltage protection before reference establishment. The circuit does not require an additional reference voltage, and the supply voltage of the circuit is relatively low, only slightly higher than the reference, and is particularly suitable for use in low-voltage circuits to improve the yield, accuracy and reliability of the overall circuit.

[0045] The above embodiments further illustrate the purpose, technical solutions and advantages of the present invention in detail. It should be understood that the above embodiments are only preferred implementation modes of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made to the present invention within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A bandgap reference circuit with undervoltage protection, characterized in that: It includes a bandgap reference generating circuit and a reference undervoltage protection circuit. The bandgap reference generating circuit is used to generate an accurate and stable reference voltage. When the output voltage of the bandgap reference generating circuit is less than the set voltage value, the reference undervoltage protection circuit shuts down the subsequent circuit to perform undervoltage protection.

2. A bandgap reference circuit with undervoltage protection according to claim 1, characterized in that: The bandgap reference generation circuit includes first to third resistors, first to fourth MOS transistors, seventh to eighth MOS transistors, and first to fourth transistors, wherein: The sources of the first to fourth MOS tubes are connected to the power supply terminal, the gates of the first, second and fourth MOS tubes are connected to the first enable signal, and the drain of the first MOS tube, the base of the first transistor and the drain of the seventh MOS tube are connected together; The drain of the second MOS tube, the collector of the second transistor, and the gate of the seventh MOS tube are connected together; The drain of the third MOS tube, the collector of the first transistor, and one end of the first resistor are connected together as a bandgap reference voltage output end; The drain of the fourth MOS tube, the collector of the fourth transistor, and the gate of the eighth MOS tube are connected together; The source electrodes of the seventh MOS tube and the eighth MOS tube, and the emitters of the first transistor and the third transistor are grounded; The drain of the eighth MOS transistor, the emitters of the second transistor and the fourth transistor are connected together; The base of the second transistor is connected with one end of the second resistor and one end of the third resistor; The base and collector of the third transistor and the other end of the third resistor are connected together; The base of the fourth transistor is connected with the other end of the second resistor and the other end of the first resistor.

3. A bandgap reference circuit with undervoltage protection according to claim 2, characterized in that: The first to fourth MOS tubes are N-type MOS tubes, and the seventh to eighth MOS tubes are P-type MOS tubes.

4. A bandgap reference circuit with undervoltage protection according to claim 2, characterized in that: The emitter area of ​​the fourth transistor: the emitter area of ​​the second transistor = 1:4, the emitter current of the fourth transistor: the emitter current of the second transistor = 2:

1.

5. A bandgap reference circuit with undervoltage protection according to claim 2, characterized in that: The resulting bandgap reference voltage value is expressed as: Where VBG represents the generated bandgap reference voltage value; V BE,Q3 represents the BE junction voltage of the third transistor; V T Indicates the voltage equivalent of temperature. At room temperature, V T =26mV; R1 is the resistance value of the first resistor, R2 is the resistance value of the second resistor, and R3 is the resistance value of the third resistor.

6. A bandgap reference circuit with undervoltage protection according to claim 1, characterized in that: The reference undervoltage protection circuit includes fifth to ninth resistors, fifth to sixth MOS tubes, ninth to tenth MOS tubes, fifth to seventh transistors, and first to second inverters, wherein: The fifth to sixth MOS tube sources are connected to the power supply terminal, the fifth to sixth MOS tube gates are connected to the third enable terminal, the fifth MOS tube drain, the ninth to tenth MOS tube sources, one end of the fifth resistor and one end of the seventh resistor are connected together and connected to the bandgap reference output voltage; The drain of the sixth MOS tube, the collector of the seventh transistor, and the input end of the second inverter are connected together and serve as an undervoltage protection output end; The gate of the ninth MOS tube is connected to the output end of the first inverter and the gate of the tenth MOS tube, and the drain of the ninth MOS tube is connected to the other end of the fifth resistor and one end of the sixth resistor; The drain of the tenth MOS tube is connected with the other end of the seventh resistor and one end of the eighth resistor; The collector and base of the fifth transistor, the other end of the sixth resistor, and the base of the sixth transistor are connected together; the emitter of the fifth transistor, one end of the ninth resistor, and the emitter of the seventh transistor are grounded; The emitter of the sixth transistor is connected to the other end of the ninth resistor, and the collector of the sixth transistor is connected to the other end of the eighth resistor and the base of the seventh transistor; The first and second inverters are cascaded.

7. A bandgap reference circuit with undervoltage protection according to claim 6, characterized in that: When the bandgap reference output voltage is greater than When the undervoltage protection output terminal outputs a low level, the circuit works normally; When the bandgap reference output voltage is less than When the undervoltage protection output terminal outputs a high level, the subsequent circuit module is turned off. BE,Q5 represents the BE junction voltage of the fifth transistor, V T Indicates the voltage equivalent of temperature; R5, R6, R9 respectively represent the resistance values ​​of the fifth resistor R5, the sixth resistor R6, and the ninth resistor R9.

8. A bandgap reference circuit with undervoltage protection according to claim 6, characterized in that: The emitter area of ​​the fifth transistor: the emitter area of ​​the sixth transistor=1:

8.

9. The bandgap reference circuit with undervoltage protection according to claim 6, characterized in that: The fifth to eighth resistors have the same resistance value, ensuring that the emitter currents of the fifth transistor and the sixth transistor are equal.

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