TW202040303A - Voltage regulation circuit - Google Patents

Abstract

A voltage regulation circuit is suitable to provide an output voltage to a core circuit. The voltage regulation circuit includes a pad, a pull-low unit, a first controlling unit, a second controlling unit and a voltage regulation circuit. The pad receives and provides an input voltage. The pull-low unit generates a pull-low voltage according to the input voltage. The first controlling unit generates a first controlling signal according to the input voltage and the pull-low voltage. The second controlling unit generates a second controlling signal according to the input voltage and the first controlling signal. The voltage regulation unit regulates the input voltage according to the first controlling signal and the second controlling signal, so as to generate the output voltage.

Description

Voltage adjustment circuit

The present invention relates to an adjustment circuit, in particular to a voltage adjustment circuit.

With the advancement of technology, there are more and more types and functions of electronic devices. Generally speaking, there are many integrated circuits inside electronic devices. Each integrated circuit may receive many operating voltages, all of which are different.

However, when a certain input voltage exceeds the operating voltage required by the integrated circuit, if the integrated circuit uses the input voltage, the integrated circuit is prone to malfunction or damage. Therefore, there is still room for improvement in the design of the above architecture.

The present invention provides a voltage adjustment circuit, so as to avoid providing unsuitable output voltage to the core power, causing the core circuit to malfunction or damage, so as to increase the safety and stability of the circuit operation.

The present invention provides a voltage adjustment circuit suitable for providing output voltage to a core circuit. The voltage adjustment circuit includes a pad, a pull-down unit, a first control unit, a second control unit, and a voltage adjustment circuit. The pad receives and provides the input voltage. The pull-down unit is coupled to the pad, receives an input voltage, and generates a pull-down voltage according to the input voltage. The first control unit is coupled to the pad and the pull-down unit, receives the input voltage and the pull-down voltage, and generates a first control signal according to the input voltage and the pull-down voltage. The second control unit is coupled to the pad and the first control circuit, receives the input signal and the first control signal, and generates the second control signal according to the input voltage and the first control signal. The voltage adjustment unit is coupled to the pad, the first control unit and the second control unit, receives the input voltage, the first control signal and the second control signal, and adjusts the input voltage according to the first control signal and the second control signal, To generate output voltage.

The voltage adjustment circuit disclosed in the present invention generates a pull-down voltage based on the input voltage through the pull-down unit, the first control unit generates a first control signal based on the input voltage and the pull-down voltage, and the second control unit generates a first control signal based on the input voltage and the first control signal. A second control signal is generated, and the voltage adjustment unit adjusts the input voltage according to the first control signal and the second control signal to generate an output voltage. In this way, it is possible to prevent the voltage regulation circuit from providing an unsuitable output voltage to the core circuit, causing the core circuit to malfunction or damage, so as to increase the safety and stability of the circuit operation.

In the embodiments listed below, the same reference numerals will be used to represent the same or similar elements or components.

Figure 1 is a schematic diagram of an embodiment according to the present invention. Please refer to FIG. 1, the voltage adjustment circuit 100 of this embodiment is suitable for providing the output voltage VOUT to the core circuit 160, so that the core circuit 160 can obtain the required operating voltage to maintain normal operation.

The voltage adjustment circuit 100 includes a pad 110, a pull-down unit 120, a first control unit 130, a second control unit 140, and a voltage adjustment unit 150. The pad 110 receives and provides the input voltage VIN. The pull-down unit 120 is coupled to the pad 110, receives the input voltage VIN, and generates the pull-down voltage VD according to the input voltage VIN.

The first control unit 130 is coupled to the pad 110 and the pull-down unit 120, receives the input voltage VIN and the pull-down voltage VD, and generates the first control signal CS1 according to the input voltage VIN and the pull-down voltage VD. The second control unit 140 is coupled to the pad 110 and the first control circuit 130, receives the input signal VIN and the first control signal CS1, and generates the second control signal CS2 according to the input signal VIN and the first control signal CS1.

The voltage adjustment unit 150 is coupled to the pad 110, the first control unit 130, and the second control unit 140, receives the input voltage VIN, the first control signal CS1 and the second control signal CS2, and controls it according to the first control signal CS1 and the second control signal. The signal CS2 adjusts the input voltage VIN to generate the output voltage VOUT.

When the input voltage VIN is less than or equal to the preset value, the first control unit 130 and the second control unit 140 adjust the voltage levels of the first control signal CS1 and the second control signal CS2, respectively, so that the voltage adjustment unit 150 maintains the input voltage VIN To generate the output voltage VOUT. The aforementioned preset value is, for example, the operating voltage required by the core circuit 160, and the preset value is, for example, 1.8V.

That is, when the input voltage VIN is less than or equal to the preset value (for example, 1.8V), it means that the input voltage VIN can be supplied to the core circuit 160, and the first control unit 130 and the second control unit 140 will adjust the first control signal The voltage levels of CS1 and the second control signal CS2. Then, the voltage adjustment unit 150 maintains the voltage level of the input voltage VIN according to the voltage levels of the first control signal CS1 and the second control signal CS2 to generate the output voltage VOUT that is the same as the voltage level of the input voltage VIN, and This output voltage is provided to the core circuit 160.

In addition, when the input voltage VIN is greater than the preset value, the first control unit 130 and the second control unit 140 adjust the voltage levels of the first control signal CS1 and the second control signal CS2, respectively, so that the voltage adjustment unit 150 reduces the input voltage To generate the output voltage VOUT.

That is, when the input voltage VIN is greater than the preset value (for example, 1.8V), it means that the input voltage VIN is greater than the operating voltage required by the core circuit 160, and the first control unit 130 and the second control unit 140 will adjust the first control signal The voltage levels of CS1 and the second control signal CS2. Then, the voltage adjustment unit 150 adjusts the voltage level provided by the input voltage VIN according to the voltage levels of the first control signal CS1 and the second control signal CS2, for example, reduces the voltage level provided by the input voltage VIN to It is the same as the preset value to generate an output voltage VOUT that is the same as the preset value, and the output voltage VOUT is provided to the core circuit 160.

It can be seen from this that when the input voltage VIN is less than or equal to the preset value, the voltage adjustment circuit 100 directly uses the input voltage VIN as the output voltage VOUT, and provides the output voltage VOUT to the core circuit 160. When the input voltage VIN is greater than the preset value, the voltage adjustment circuit 100 reduces the voltage level provided by the input voltage VIN, and uses the reduced voltage level as the output voltage VOUT and provides the output voltage VOUT to the core circuit 160 . In this way, it is possible to prevent the voltage adjustment circuit 100 from providing an unsuitable output voltage VOUT to the core circuit 160, causing the core circuit 160 to malfunction or damage, so as to increase the safety and stability of the circuit operation.

FIG. 2 is a detailed circuit diagram of a voltage adjustment circuit according to an embodiment of the invention. Please refer to FIG. 2, the pull-down unit 120 includes an inverter 210 and a transistor N1. The inverter 210 has an input terminal and an output terminal. The input terminal of the inverter 210 is coupled to the pad 110 to receive the input voltage VIN. The output terminal of the inverter 210 generates an inverted signal.

The transistor N1 has a first end, a second end, a third end and a fourth end. The first terminal of the transistor N1 is coupled to the output terminal of the inverter 210, the second terminal of the transistor N1 generates the pull-down voltage VD, and the third terminal and the fourth terminal of the transistor N1 receive the first voltage V1. Wherein, the first voltage V1 is, for example, the ground voltage GND.

Furthermore, the inverter 210 includes a transistor P1 and a transistor N2. The transistor P1 has a first end, a second end, a third end and a fourth end. The first terminal of the transistor P1 serves as the input terminal of the inverter 210 to receive the input voltage VIN. The second terminal of the transistor P1 is used as the output terminal of the inverter 210 to generate a reverse signal. The third terminal and the fourth terminal of the transistor P1 receive the second voltage V2. Wherein, the second voltage V2 may be a working voltage, for example, 1.8V.

The transistor N2 has a first end, a second end, a third end and a fourth end. The first end of transistor N2 is coupled to the first end of transistor P1, the second end of transistor N2 is coupled to the second end of transistor P1, and the third and fourth ends of transistor N2 receive the first voltage V1. (That is, the ground voltage GND).

In this embodiment, the aforementioned transistors N1 and N2 are, for example, N-type transistors. In addition, the first terminals of the transistors N1 and N2 are, for example, the gate terminals of the N-type transistors, and the second terminals of the transistors N1 and N2 are, for example, the drain terminals of the N-type transistors. The transistors N1 and N2 are The third terminal of N2 is, for example, the source terminal of an N-type transistor, and the fourth terminals of transistors N1 and N2 are, for example, the base terminal of an N-type transistor.

In addition, the aforementioned transistor P1 is, for example, a P-type transistor. In addition, the first terminal of the transistor P1 is, for example, the gate terminal of a P-type transistor, the second terminal of the transistor P1 is, for example, the drain terminal of the P-type transistor, and the third terminal of the transistor P1 is, for example, the P-type transistor. The source terminal is the fourth terminal of the transistor P1, such as the base terminal of the P-type transistor.

The first control unit 130 includes a transistor N3, a transistor N4, a transistor N5, and a transistor P2. The transistor N3 has a first end, a second end, a third end and a fourth end. The first terminal of the transistor N3 receives the second voltage V2 (that is, the working voltage is 1.8V), the second terminal of the transistor N3 is coupled to the pad 110, and the fourth terminal of the transistor N3 receives the first voltage V1 (that is, the ground voltage GND). ).

The transistor N4 has a first end, a second end, a third end and a fourth end. The first terminal and the second terminal of the transistor N4 are coupled to the third terminal of the transistor N3, the third terminal of the transistor N4 generates the first control signal CS1, and the fourth terminal of the transistor N4 receives the first voltage V1 (ie, grounded) Voltage GND).

The transistor N5 has a first end, a second end, a third end and a fourth end. The first terminal of the transistor N5 receives the second voltage V2 (ie, the working voltage is 1.8V), the second terminal of the transistor N5 is coupled to the third terminal of the transistor N4, and the third terminal of the transistor N5 is coupled to the pull-down unit 120, To receive the pull-down voltage VD, the fourth terminal of the transistor N5 receives the first voltage V1 (ie, the ground voltage GND).

The transistor P2 has a first end, a second end, a third end and a fourth end. The first terminal of the transistor P2 receives the second voltage V2 (ie, the working voltage is 1.8V), the second terminal of the transistor P2 is coupled to the second terminal of the transistor N5, and the third terminal of the transistor P2 is coupled to the pad 110, The fourth terminal of the transistor P2 receives the second control signal CS2.

In this embodiment, the aforementioned transistors N3, N4, and N5 are, for example, N-type transistors. In addition, the first ends of transistors N3, N4, and N5 are, for example, gate terminals of N-type transistors, and the second ends of transistors N3, N4, and N5 are, for example, drain terminals of N-type transistors. Transistors N3, N4, and The third terminal of N5 is, for example, the source terminal of an N-type transistor, and the fourth terminals of transistors N3, N5, and N5 are, for example, the base terminal of an N-type transistor.

In addition, the aforementioned transistor P2 is, for example, a P-type transistor. In addition, the first terminal of transistor P2 is, for example, the gate terminal of a P-type transistor, the second terminal of transistor P2 is, for example, the drain terminal of a P-type transistor, and the third terminal of transistor P2 is, for example, the terminal of P-type transistor. The source terminal is the fourth terminal of the transistor P2, such as the base terminal of the P-type transistor.

The second control unit 140 includes a transistor P3 and a transistor P4. The transistor P3 has a first end, a second end, a third end and a fourth end. The first terminal of the transistor P3 receives the first control signal CS1, the second terminal of the transistor P3 is coupled to the fourth terminal and generates a second control signal CS2, and the third terminal of the transistor P3 receives the second voltage V2 (ie Working voltage 1.8V).

The transistor P4 has a first end, a second end, a third end and a fourth end. The first terminal of the transistor P4 receives the second voltage V2 (ie, the working voltage is 1.8V), the second terminal and the fourth terminal of the transistor P4 are coupled to the third terminal of the transistor P3, and the third terminal of the transistor P4 is coupled接垫110。 Connecting pad 110.

In this embodiment, the aforementioned transistors P3 and P4 are, for example, P-type transistors. In addition, the first terminals of transistors P3 and P4 are, for example, the gate terminals of P-type transistors, the second terminals of transistors P3 and P4 are, for example, the drain terminals of P-type transistors, and the third terminals of transistors P3 and P4 are, for example, It is the source terminal of the P-type transistor, and the fourth terminals of the transistors P3 and P4 are, for example, the base terminal of the P-type transistor.

The voltage adjustment unit 150 includes a transistor P5 and a transistor N6. The transistor P5 has a first end, a second end, a third end and a fourth end. The first terminal of the transistor P5 receives the first control signal CS1, the second terminal of the transistor P5 generates the output voltage VOUT, the third terminal of the transistor P5 is coupled to the pad 110 to receive the input voltage VIN, the second terminal of the transistor P5 The four terminals receive the second control signal CS2.

The transistor N6 has a first end, a second end, a third end and a fourth end. The first end of transistor N6 receives the first control signal CS1, the second end of transistor N6 is coupled to the second end of transistor P5, the third end of transistor N6 is coupled to the third end of transistor P5, and the second end of transistor N6 is coupled to the third end of transistor P5. The fourth terminal of N6 receives the first voltage V1 (ie, the ground voltage GND).

In this embodiment, the aforementioned transistor P5 is, for example, a P-type transistor. In addition, the first terminal of transistor P5 is, for example, the gate terminal of a P-type transistor, the second terminal of transistor P5 is, for example, the drain terminal of a P-type transistor, and the third terminal of transistor P5 is, for example, the drain terminal of a P-type transistor. The source terminal is the fourth terminal of the transistor P5, such as the base terminal of the P-type transistor.

In addition, the aforementioned transistor N6 is, for example, an N-type transistor. In addition, the first terminal of transistor N6 is, for example, the gate terminal of an N-type transistor, the second terminal of transistor N6 is, for example, the drain terminal of an N-type transistor, and the third terminal of transistor N6 is, for example, the terminal of an N-type transistor. The source terminal is the fourth terminal of the transistor N6, such as the base terminal of the N-type transistor.

In addition, in this embodiment, the thickness of the process parameters used by the aforementioned transistors N1~N6 and P1~P6 is larger than that of ordinary transistors. Therefore, the threshold voltages (Vth) of the transistors N1~N6 and P1~P6 are also larger. bigger. Moreover, the transistors N1 to N6 and P1 to P6 are, for example, transistors that can work at 5V.

The above has described the internal components of the voltage adjustment circuit 100 and their configuration relationships. The following will list some embodiments to illustrate the operation of the voltage adjustment circuit 100.

FIG. 3 is a schematic diagram of the operation of the voltage adjustment circuit according to an embodiment of the present invention. Assume that the input voltage VIN is 0V, that is, the input voltage VIN is less than the preset value.

First, since the input voltage is 0V, the transistor P1 of the inverter 210 is turned on and the transistor N2 of the inverter 210 is not turned on, the inverted signal output by the output terminal of the inverter 210 is the second voltage V2 (ie Working voltage 1.8V). Moreover, since the inverted signal is the second voltage V2 (ie, the working voltage is 1.8V), the transistor N1 is turned on, and the pull-down voltage VD generated by the second end of the transistor N1 is the first voltage V1 (ie, the ground voltage GND), That is, the pull-down unit 120 generates the pull-down voltage VD of the first voltage V1.

In addition, since the input voltage VIN is 0V, the transistor N3 is turned on, and the transistor N4 and the transistor P2 are not turned on. Moreover, since the first terminal (gate terminal) of transistor N5 receives the second voltage V2 (that is, the working voltage 1.8V) and the third terminal (source terminal) of transistor N5 receives the pull-down voltage VD of the first voltage V1, the electric When the transistor N5 is turned on, the first control signal CS1 generated by the second terminal of the transistor N5 is the first voltage V1 (ie, the ground voltage GND), that is, the first control unit 130 generates the first control signal CS1 of the first voltage V1.

Since the first terminal (gate terminal) of the transistor P3 receives the first control signal CS1 of the first voltage V1 and the third terminal (source terminal) of the transistor P3 receives the second voltage V2 (that is, the working voltage 1.8V), the electric When the transistor P3 is turned on, the second control signal CS2 generated by the second terminal (drain terminal) of the transistor P3 is the second voltage V2 (ie working voltage 1.8V), that is, the second control unit 140 generates the second voltage V2 (ie Working voltage 1.8V) the second control signal CS2. In addition, since the first terminal (gate terminal) of transistor P4 receives the second voltage V2 (that is, the working voltage 1.8V) and the third terminal (source terminal) of transistor P4 receives the input voltage VIN of 0V, the transistor P4 is not Conduction.

Then, since the first control signal CS1 is the first voltage V1 (that is, the ground voltage GND) and the second control signal CS2 is the second voltage V2 (that is, the working voltage is 1.8V), the transistor P5 and the transistor N6 are turned on, then the voltage The adjustment unit 150 uses the input voltage VIN of 0V as the output voltage VOUT, and provides the output voltage VOUT of 0V to the core circuit 160.

FIG. 4 is a schematic diagram of the operation of the voltage adjustment circuit according to another embodiment of the present invention. Assume that the input voltage VIN is 1.8V, that is, the input voltage VIN is equal to the preset value.

First, since the input voltage is 1.8V, the transistor P1 of the inverter 210 is not turned on and the transistor N2 of the inverter 210 is turned on, the inverted signal output by the output terminal of the inverter 210 is the first voltage V1( That is, the ground voltage GND). Moreover, since the inverted signal is the first voltage V1 (ie, the ground voltage GND), the transistor N1 is not turned on, and the pull-down unit 120 does not generate the pull-down voltage VD.

In addition, since the input voltage VIN is 1.8V, the transistor N3 and the transistor N4 are turned on, and the transistor P2 is not turned on. Moreover, since the transistor N3 and the transistor N4 are turned on, the first control signal CS1 generated by the third terminal (source terminal) of the transistor N4 is 1.8-2Vth, where Vth is the threshold voltage of the transistors N3 and N4.

Since the first terminal (gate terminal) of transistor P3 receives the (1.8-2Vth) first control signal CS1 and the third terminal (source terminal) of transistor P3 receives the second voltage V2 (that is, the working voltage 1.8V), The transistor P3 is turned on, and the second control signal CS2 generated by the second terminal (drain terminal) of the transistor P3 is the second voltage V2 (that is, the working voltage 1.8V), that is, the second control unit 140 generates the second voltage V2 ( That is, the second control signal CS2 with a working voltage of 1.8V). Moreover, since the first terminal (gate terminal) of transistor P4 receives the second voltage V2 (that is, the working voltage 1.8V) and the third terminal (source terminal) of transistor P4 receives the input voltage VIN of 1.8V, the transistor P4 No conduction.

Then, since the first control signal CS1 is (1.8-2Vth) and the second control signal CS2 is the second voltage V2 (that is, the working voltage is 1.8V), the transistor P5 and the transistor N6 are turned on, and the voltage adjustment unit 150 starts to generate The output voltage VOUT. Moreover, when the transistor P5 and the transistor N6 are turned on, the output voltage VOUT is provided by the transistor P5 and the transistor N6 at the same time.

Then, when the output voltage VOUT reaches 1.8-Vth, the transistor N6 is not turned on and the transistor P5 is still turned on, so that the output voltage VOUT is still provided by the transistor P5 until the output voltage VOUT reaches the voltage level of the 1.8V input voltage VIN. Same bit. In other words, the voltage adjustment unit 150 can provide an output voltage VOUT (ie, 1.8V) at the same voltage level as the input voltage VIN, and provide the output voltage VOUT to the core circuit 160.

FIG. 5 is a schematic diagram of the operation of a voltage adjustment circuit according to another embodiment of the present invention. Assume that the input voltage VIN is 3.3V, that is, the input voltage VIN is greater than the preset value.

First, since the input voltage VIN is 3.3V, the transistor P1 of the inverter 210 is not turned on and the transistor N2 of the inverter 210 is turned on, the inverted signal output by the output terminal of the inverter 210 is the first voltage V1 (That is, the ground voltage GND). Moreover, since the inverted signal is the first voltage V1 (ie, the ground voltage GND), so that the transistor N1 is not turned on, the pull-down unit 120 does not generate the pull-down voltage VD.

In addition, since the input voltage VIN is 3.3V and the transistor P2 is turned on, the first control signal CS1 generated by the transistor P2 is 3.3V. Moreover, since the input voltage VIN is 3.3 and the first control signal CS1 is 3.3V, the transistors N3 and N4 are not conductive.

Since the first terminal (gate terminal) of the transistor P3 receives the first control signal CS1 of 3.3V and the third terminal (source terminal) of the transistor P3 receives the second voltage V2 (that is, the working voltage 1.8V), the transistor P3 No conduction. Moreover, since the first terminal (gate terminal) of transistor P4 receives the second voltage V2 (that is, the working voltage 1.8V) and the third terminal (source terminal) of transistor P4 receives the input voltage VIN of 3.3V, the transistor P4 When turned on, the second control signal CS2 generated by the second terminal (drain terminal) of the transistor P4 is the input voltage VIN of 3.3V, that is, the second control unit 140 generates the second control signal CS2 of 3.3V.

Then, since the first control signal CS1 is 3.3V and the second control signal CS2 is 3.3V, the transistor P5 is not turned on and the transistor N6 is turned on, the voltage adjustment unit 150 will pass the threshold voltage of the transistor N6 to change the input voltage The voltage level of 3.3V provided by VIN is reduced, for example, 3.3V-Vth, so that the adjusted voltage level (ie, 3.3V-Vth) is used as the output voltage VOUT. Among them, Vth is the threshold voltage of transistor N6.

Moreover, the output voltage VOUT generated by the voltage adjustment unit 150 is, for example, the same as the preset value, and the output voltage VOUT is provided to the core circuit 160. In this way, it is possible to prevent the voltage adjustment circuit 100 from providing an unsuitable output voltage VOUT to the core circuit 160, causing the core circuit 160 to malfunction or damage, so as to increase the safety and stability of the circuit operation.

To sum up, the voltage adjustment circuit disclosed in the present invention generates a pull-down voltage based on the input voltage through the pull-down unit, the first control unit generates the first control signal based on the input voltage and the pull-down voltage, and the second control unit generates the first control signal based on the input voltage and The first control signal generates a second control signal, and the voltage adjustment unit adjusts the input voltage according to the first control signal and the second control signal to generate an output voltage. In this way, it is possible to prevent the voltage adjustment circuit from providing an unsuitable output voltage to the core circuit, causing the core circuit to malfunction or damage, so as to increase the safety and stability of the circuit operation.

Although the present invention is disclosed as above by embodiments, it is not intended to limit the scope of the present invention. Anyone with ordinary knowledge in the technical field can make some changes and modifications without departing from the spirit and scope of the present invention. Therefore, the protection scope of the present invention shall be subject to those defined by the attached patent application scope.

100: voltage adjustment circuit 110: pad 120: pull-down unit 130: first control unit 140: second control unit 150: voltage adjustment unit 160: core circuit N1~N6, P1~P6: transistor VIN: input voltage VOUT: Output voltage CS1: first control signal CS2: second control signal V1: first voltage V2: second voltage VD: pull-down voltage

FIG. 1 is a schematic diagram of a voltage adjusting circuit according to an embodiment of the invention. FIG. 2 is a detailed circuit diagram of a voltage adjustment circuit according to an embodiment of the invention. FIG. 3 is a schematic diagram of the operation of the voltage adjustment circuit according to an embodiment of the present invention. FIG. 4 is a schematic diagram of the operation of the voltage adjustment circuit according to another embodiment of the present invention. FIG. 5 is a schematic diagram of the operation of a voltage adjustment circuit according to another embodiment of the present invention.

100: Voltage adjustment circuit

110: pad

120: drop-down unit

130: The first control unit

140: second control unit

150: Voltage adjustment circuit

160: core circuit

VIN: input voltage

VOUT: output voltage

CS1: The first control signal

CS2: second control signal

VD: pull-down voltage

Claims (8)

A voltage adjustment circuit is suitable for providing an output voltage to a core circuit. The voltage adjustment circuit includes: a pad, receiving and providing an input voltage; a pull-down unit, coupled to the pad, receiving the input voltage, and according to The input voltage generates a pull-down voltage; a first control unit, coupled to the pad and the pull-down unit, receives the input voltage and the pull-down voltage, and generates a first control signal according to the input voltage and the pull-down voltage A second control unit, coupled to the pad and the first control circuit, receives the input signal and the first control signal, and generates a second control signal according to the input voltage and the first control signal; and A voltage adjustment unit, coupled to the pad, the first control unit, and the second control unit, receives the input voltage, the first control signal, and the second control signal, and based on the first control signal and the second control signal The second control signal adjusts the input voltage to generate the output voltage. According to the voltage adjustment circuit described in claim 1, wherein the pull-down unit includes: an inverter having an input terminal and an output terminal, and the input terminal of the inverter is coupled to the pad to receive The input voltage, the output terminal of the inverter generates an inverted signal; and a first transistor having a first terminal, a second terminal, a third terminal, and a fourth terminal. The first terminal of the crystal is coupled to the output terminal of the inverter, the second terminal of the first transistor generates the pull-down voltage, and the third terminal and the fourth terminal of the first transistor receive a first One voltage. The voltage adjustment circuit described in item 2 of the scope of patent application, wherein the inverter includes: a second transistor having a first terminal, a second terminal, a third terminal and a fourth terminal, the first The first terminal of the two transistors serves as the input terminal of the inverter, the second terminal of the second transistor serves as the output terminal of the inverter, the third terminal of the second transistor and the The fourth terminal receives a second voltage; and a third transistor having a first terminal, a second terminal, a third terminal, and a fourth terminal. The first terminal of the third transistor is coupled to the The first end of the second transistor, the second end of the third transistor is coupled to the second end of the second transistor, and the third end and the fourth end of the third transistor receive a First voltage. According to the voltage adjustment circuit described in claim 1, wherein the first control unit includes: a first transistor having a first terminal, a second terminal, a third terminal and a fourth terminal, the The first terminal of the first transistor receives a second voltage, the second terminal of the first transistor is coupled to the pad, and the fourth terminal of the first transistor receives a first voltage; a second The transistor has a first end, a second end, a third end, and a fourth end. The first end and the second end of the second transistor are coupled to the third end of the first transistor Terminal, the third terminal of the second transistor generates the first control signal, the fourth terminal of the second transistor receives a first voltage; a third transistor has a first terminal, a second terminal Terminal, a third terminal and a fourth terminal, the first terminal of the third transistor receives the second voltage, and the second terminal of the third transistor is coupled to the third terminal of the second transistor , The third end of the third transistor is coupled to the pull-down unit to receive the pull-down voltage, the fourth end of the third transistor receives a first voltage; and a fourth transistor has a first Terminal, a second terminal, a third terminal, and a fourth terminal, the first terminal of the fourth transistor receives the second voltage, and the second terminal of the fourth transistor is coupled to the third transistor The third end of the fourth transistor is coupled to the pad, and the fourth end of the fourth transistor receives the second control signal. According to the voltage adjustment circuit described in claim 1, wherein the second control unit includes: a first transistor having a first terminal, a second terminal, a third terminal and a fourth terminal, the The first terminal of the first transistor receives the first control signal, the second terminal of the first transistor is coupled to the fourth terminal and generates the second control signal, the second terminal of the first transistor Three terminals receive a second voltage; and a second transistor having a first terminal, a second terminal, a third terminal, and a fourth terminal. The first terminal of the second transistor receives the second Voltage, the second terminal and the fourth terminal of the second transistor are coupled to the third terminal of the first transistor, and the third terminal of the second transistor is coupled to the pad. According to the voltage adjustment circuit described in claim 1, wherein the voltage adjustment unit includes: a first transistor having a first end, a second end, a third end and a fourth end, the first transistor The first terminal of a transistor receives the first control signal, the second terminal of the first transistor generates the output voltage, and the third terminal of the first transistor is coupled to the pad to receive the input Voltage, the fourth terminal of the first transistor receives the second control signal; and a second transistor having a first terminal, a second terminal, a third terminal and a fourth terminal, the second The first end of the transistor receives the first control signal, the second end of the second transistor is coupled to the second end of the first transistor, and the third end of the second transistor is coupled to the The third terminal of the first transistor and the fourth terminal of the second transistor receive a first voltage. For example, the voltage adjustment circuit described in item 1 of the scope of patent application, wherein when the input voltage is less than or equal to a preset value, the first control unit and the second control unit adjust the first control signal and the second control signal respectively. The voltage level of the control signal enables the voltage adjustment unit to maintain the voltage level of the input voltage to generate the output voltage. The voltage adjustment circuit described in item 1 of the scope of patent application, wherein when the input voltage is greater than the preset value, the first control unit and the second control unit respectively adjust the first control signal and the second control signal The voltage level of the voltage adjustment unit reduces the voltage level provided by the input voltage to generate the output voltage.

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