Bandgap reference circuit with under-voltage protection

Abstract

The present application belongs to the field of integrated circuit, and particularly relates to a band gap reference circuit with under-voltage protection, comprising a band gap reference generating circuit and a reference under-voltage protection circuit, the band gap reference generating circuit is used for generating an accurate and stable reference voltage, and the under-voltage protection is realized by shutting down the subsequent circuit through the reference under-voltage protection circuit when the output voltage of the band gap reference generating circuit is less than a set voltage value. The circuit of the present application can not only generate an accurate band gap reference voltage, but also realize under-voltage protection before the reference is established.

Description

Technical Field

[0001] This invention belongs to the field of integrated circuits, and specifically relates to a bandgap reference circuit with undervoltage protection. Background Technology

[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 under undervoltage conditions, thereby achieving voltage monitoring and improving the overall circuit yield, accuracy, and reliability.

[0003] like Figure 1 This is a conventional bandgap reference circuit, including PMOS transistors M1 and M2, NPN transistors Q1 to Q6, resistors R1 to R3, and capacitor C1. Q3 and Q4 are the reference cores, used to generate the bandgap reference voltage V. OUT Q5 and Q6 provide clamping; PMOS transistors M2 and M1 form a current mirror; 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, R1, R3 are Figure 1 The resistance values ​​of resistors R1 and R3 in the middle, V T This is the voltage equivalent of temperature.

[0006] Traditional bandgap reference circuits can only generate a reference voltage and do not have an undervoltage indication function.

[0007] like Figure 2 This is a traditional undervoltage protection circuit, essentially a voltage comparator, comprising PMOS transistors M1-M4 and NMOS transistors M5-M7. The gate of M3 serves as the comparator's reference voltage VREF, typically the system circuit's reference voltage. The gate of M4 serves as the voltage to be compared, VM. UVLO is the undervoltage protection output. When VM is lower than the reference voltage, UVLO outputs a low level; when VM rises above the reference voltage, UVLO outputs a high level, indicating normal circuit operation. Traditional undervoltage protection circuits require an additional reference voltage VREF and a relatively high supply voltage VIN, making them unsuitable for undervoltage protection before a reference is established or under low supply voltage conditions. Summary of the Invention

[0008] To overcome the shortcomings of the above-mentioned bandgap reference circuits, this invention proposes a novel bandgap reference circuit with undervoltage protection, including a bandgap reference generation circuit and a reference undervoltage protection circuit. The bandgap reference generation circuit is used to generate an accurate and stable reference voltage. When the output voltage of the bandgap reference generation circuit is less than the set voltage value, the reference undervoltage protection circuit shuts down the subsequent circuit for undervoltage protection.

[0009] The beneficial effects of this invention are as follows:

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

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

[0012] (3) The bandgap reference undervoltage protection circuit of the present invention can meet the low-voltage operation requirements. Attached Figure Description

[0013] Figure 1 A traditional bandgap reference circuit;

[0014] Figure 2 A traditional undervoltage protection circuit;

[0015] Figure 3 The bandgap reference generation 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 diagram, 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; and R9 is the ninth resistor.

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

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

[0022] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

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

[0024] This invention provides a bandgap reference circuit with undervoltage protection, comprising a bandgap reference generation circuit and a reference undervoltage protection circuit. The bandgap reference generation circuit includes first resistors R1 to third resistors R3, first MOSFETs M1 to fourth MOSFETs M4, seventh MOSFETs M7 and eighth MOSFETs M8, first transistors Q1 to fourth transistors Q4, a power supply voltage terminal VIN, a first enable signal EN1 and a second enable signal EN2, a bandgap reference output voltage terminal VBG, and a ground terminal GND. The first MOSFETs M1 to fourth MOSFETs M4 are P-type MOSFETs, the seventh MOSFETs M7 and eighth MOSFETs M8 are N-type MOSFETs, and the first transistors Q1 to fourth transistors Q4 are NPN type transistors. Figure 3 ,in:

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

[0026] The drain of the first MOS transistor M1, the drain of the seventh MOS transistor M7, and the base of the first transistor Q1 are connected. The gate of the seventh MOS transistor M7, the drain of the second MOS transistor 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. 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. 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 MOSFET M4, and the gate of the eighth MOSFET M8 are connected. The sources of the seventh MOSFET M7 and the eighth MOSFET 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 resistors R5 to R9 (fifth to ninth), MOSFETs M5, M6, M9, and M10 (fifth, sixth, and ninth), transistors Q5 to Q7 (fifth and seventh), inverters I1 and I2 (first and second), power supply voltage terminal VIN, enable signal EN3, bandgap reference voltage terminal VBG, undervoltage protection output terminal UVLO, and ground terminal GND. MOSFETs M5, M6, M9, and M10 are P-type MOSFETs, and transistors Q5 to Q7 are NPN type transistors. Figure 4 ,in:

[0032] The sources of the fifth MOSFET M5 and the sixth MOSFET M6 are connected to the power supply terminal VIN, and the gates of the fifth MOSFET M5 and the sixth MOSFET M6 are connected to the third enable signal EN3.

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

[0034] The drain of the ninth MOSFET 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. 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 transistor M6 and serves as the undervoltage protection output terminal UVLO.

[0037] The output terminal UVLO of the undervoltage protection is connected to the gates of the ninth MOSFET M9 and the tenth MOSFET M10 through two stages of inverters, namely the second inverter I2 and the first inverter I1.

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

[0039] This invention is a bandgap reference circuit with undervoltage protection. The circuit is divided into two parts. The first part is as follows: Figure 3 The bandgap reference generation circuit shown has a second part as follows: Figure 4 The diagram shows an undervoltage protection circuit for a bandgap reference. In the first part, the first enable terminal EN1 and the second enable terminal EN2 are at low levels. The current source branches containing the first MOSFET M1, the second MOSFET M2, the third MOSFET M3, and the fourth MOSFET M4 are turned on. The first resistor R1 to the third resistor R3, and the second transistor Q2 to the fourth transistor Q4 constitute the core structure of the bandgap. The ratio of the emitter area of ​​the fourth transistor Q4 to that of the second transistor Q2 is 1:4, and the ratio of their emitter currents is 2:1. The bandgap reference voltage VBG can be expressed as:

[0040]

[0041] Among them, V BE,Q3 V is the BE junction voltage of the third transistor Q3. T Voltage equivalent to temperature, V at room temperature T =26mV; R1, R2, and R3 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 MOSFET M8, forming a feedback loop. This loop adjusts the quiescent operating points of the fourth transistor Q4 and the second transistor Q2 to ensure the reference operates normally. The seventh MOSFET M7, the first transistor Q1, and the reference main circuit form a feedback loop to improve the reference's PSRR performance. When the bandgap reference voltage output terminal VBG decreases, the base voltage of the second transistor Q2 decreases, leading to an increase in the collector voltage of the second transistor Q2, which in turn increases the gate voltage of the seventh MOSFET M7. This, in turn, leads to a decrease in the drain voltage of the seventh MOSFET M7, which in turn decreases the base voltage of the first transistor Q1. Consequently, the collector voltage of the first transistor Q1 increases, resulting in an increase in the VBG voltage. When the bandgap reference voltage output terminal VBG increases, the adjustment process is reversed, thus stabilizing the loop.

[0043] In the second part, the third enable signal EN3 is low, the current source branches containing the fifth MOSFET M5 and the sixth MOSFET M6 are turned on, and the fifth resistor R5, the sixth resistor R6, the seventh resistor R7, and the eighth resistor R8 are of equal value, ensuring that the emitter currents of the fifth transistor Q5 and the sixth transistor Q6 are equal. The seventh transistor Q7 and the sixth MOSFET M6 form a current comparator structure, and the emitter area ratio of the fifth transistor Q5 to the sixth transistor Q6 is 1:8. The voltage at the bandgap reference voltage output terminal VBG is greater than... (where V) BE,Q5 (R5, R6, and R9 represent the BE junction voltage of the fifth transistor, respectively.) When the voltage across the bandgap reference voltage output terminal VBG is low, the current of the seventh transistor Q7 is relatively large, its drain voltage is pulled low, and the undervoltage protection output signal UVLO at the bandgap reference voltage output terminal VBG is low, indicating that the entire circuit is operating normally. Voltage hysteresis is introduced in the circuit through the fifth resistor R5, the seventh resistor R7, the ninth MOSFET M9, and the tenth MOSFET M10. As the voltage at the bandgap reference voltage output terminal VBG decreases from high, UVLO is initially low, the ninth MOSFET M9 and the tenth MOSFET M10 are turned on, and the fifth resistor R5 and the seventh resistor R7 are short-circuited. Therefore, when the voltage at the bandgap reference voltage output terminal VBG is less than... When this occurs, UVLO will output a high level, shutting down the subsequent circuit module and providing undervoltage protection.

[0044] The bandgap reference circuit with undervoltage protection of this 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 its supply voltage is low, only slightly higher than the reference, making it particularly suitable for low-voltage circuits to improve overall circuit yield, accuracy, and reliability.

[0045] The above-described embodiments further illustrate the purpose, technical solution, and advantages of the present invention. It should be understood that the above-described embodiments are merely preferred embodiments 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 within the protection scope of the present invention.

Claims

1. A bandgap reference circuit with under-voltage protection, characterized by, The application relates to a band gap reference generating circuit and a reference under-voltage protection circuit, wherein the band gap reference generating circuit is used for generating a precise and stable reference voltage, and the reference under-voltage protection circuit is used for shutting down a subsequent circuit for under-voltage protection when the output voltage of the band gap reference generating circuit is less than a set voltage value; the band gap reference generating circuit comprises first to third resistors, first to fourth MOS tubes, seventh to eighth MOS tubes, first to fourth transistors, wherein: The sources of the first to fourth MOS tubes are connected to a power supply end, the gates of the first, second and fourth MOS tubes are connected to a first enable signal, 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 band gap reference voltage output end, and the gate of the third MOS tube is connected to a second enable signal; 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 sources of the seventh and eighth MOS tubes and the emitters of the first and third transistors are grounded; The drain of the eighth MOS tube, the emitters of the second and fourth transistors are connected together; The base of the second transistor and one end of the second resistor and one end of the third resistor are connected together; 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 and the other end of the second resistor and the other end of the first resistor are connected together.

2. A bandgap reference circuit with under-voltage protection as defined in claim 1, characterized in that The first to fourth MOS tubes are P-type MOS tubes, and the seventh to eighth MOS tubes are N-type MOS tubes.

3. A bandgap reference circuit with under-voltage protection as defined in claim 2, characterized in that The emitter area of the fourth transistor: the emitter area of the second transistor = 1:4, and the emitter current of the fourth transistor: the emitter current of the second transistor = 2:

1.

4. The bandgap reference circuit with under-voltage protection of claim 1, wherein, The generated band gap reference voltage value is expressed as: wherein, represents a generated bandgap reference voltage value; represents a BE junction voltage of the third transistor; represents a voltage equivalent of temperature, at normal temperature ; R1 is a resistance value of the first resistor, R2 is a resistance value of the second resistor, and R3 is a resistance value of the third resistor.

5. The bandgap reference circuit with under-voltage protection of claim 1, wherein, The reference under-voltage protection circuit comprises 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 sources of the fifth and sixth MOS tubes are connected to the power supply end, the gates of the fifth and sixth MOS tubes are connected to a third enable end, the drain of the fifth MOS tube, the sources of the ninth and tenth MOS tubes, one end of the fifth resistor and one end of the seventh resistor are connected together and connected to the band gap 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 under-voltage 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 to 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, the collector of the sixth transistor is connected to the other end of the eighth resistor and the base of the seventh transistor; The collector of the seventh transistor is connected to the other end of the eighth resistor. The first and second inverters are connected in cascade.

6. A bandgap reference circuit with under-voltage protection as defined in claim 5, characterized in that When the bandgap reference output voltage is greater than the under-voltage protection output terminal outputs low level, and the circuit works normally. When the bandgap reference output voltage is less than the under-voltage protection output terminal outputs high level to turn off the subsequent circuit module, wherein, represents the BE junction voltage of the fifth transistor, represents the voltage equivalent of temperature; respectively represent the resistance values of the fifth resistor R5, the sixth resistor R6 and the ninth resistor R9.

7. A bandgap reference circuit with under-voltage protection as defined in claim 5, characterized in that The fifth transistor emitter area: the sixth transistor emitter area = 1:

8.

8. A bandgap reference circuit with under-voltage protection as defined in claim 5, characterized in that The fifth and eighth resistors have the same resistance, so that the emitter currents of the fifth and sixth transistors are equal.

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