JPH04220568A - Voltage detection circuit - Google Patents

Abstract

PURPOSE:To enable a voltage detection circuit which consists of a CMOS transistor to be driven by a low-consumption power. CONSTITUTION:A resistor 3 is provided within a circuit 20a which creates a reference voltage, generates a reference voltage and a voltage which is compared with the reference voltage, and then connects each voltage to an input of a voltage comparison circuit 13, thus enabling a voltage detection circuit to be driven by a low-consumption power.

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a voltage detection circuit composed of CMOS transistors, which can be driven with low power consumption. 2. Description of the Related Art FIG. 2 shows the circuit configuration of a conventional voltage detection circuit. In the figure, this voltage detection circuit connects VDD and the first
A first series circuit in which a first PMOS 1 is connected between the node 2 of the circuit, a first NMOS 5 is connected between the first node 2 and the VSS, and a second resistor is connected between the VDD and the third node 7. body 6
, a second PMO between the third node 7 and the fourth node 9
S8, a third resistor 10 between the fourth node 9 and the fifth node 11, a second N resistor between the fifth node 11 and VSS
A second series circuit to which the MOS 12 is connected, a fourth resistor 15 between VDD and the sixth node 16, and a fifth resistor 17 connected between the sixth node 16 and VSS. 3
a reference voltage generation circuit consisting of a series circuit of , and a voltage comparison circuit 13 having an output terminal 14 and connecting the fourth node 9 to one input A and the sixth node 16 to the other input B. . [0003] Also, the gate of the first PMOS1 is connected to the gate of the second PMOS1.
Connected to the gate of MOS8 and the first node 2,
The gate of the NMOS 5 is connected to the gate of the second NMOS 12 and the fifth node 11. Furthermore, the first
Compared to the second PMOS 8, the PMOS 1 has the same shape (length, width) and has a larger absolute value of the threshold voltage. 1st
The NMOS 5 and the second NMOS 12 have the same shape and the same threshold voltage. Next, the operation will be explained. First NMO
Since S5 and the second NMOS 12 constitute a current mirror circuit, the current values IO flowing through the first PMOS 1 and the second PMOS 8 are equal. Also, since the first PMOS1 and the second PMOS8 have the same shape and their gates are connected, this current value IO is the absolute value of each threshold voltage of the first PMOS1 and the second PMOS8 |VTHP
1|, |VTHP2| divided by the resistance value R0 of the resistor 6. That is, IO = (|VTHP1|-|VTHP2|)/RO
...(1) [0006] From the formula (1), the current value IO
is constant regardless of VDD. Therefore, as shown in FIG. 4, a voltage V9 with a constant difference from VSS is output to the third node 9, independent of changes in VDD. On the other hand, VDD-VSS is applied to the sixth node 16 between the fifth resistor 15 and the sixth resistor 15.
A voltage V16 resistance-divided by the resistor 17 is output. In addition, V9 is input to one input A of the voltage comparator circuit 13, and V16 is input to the other input B. When VDD is VDDTYP, V9 < V16, so the output Y is at the "L" level. is being output. VDD
decreases and becomes smaller than VDDMIN, V
9>V16, and the output Y becomes "H" level. Therefore, by looking at the output Y of the voltage comparison circuit 13, V
It is detected that DD has become smaller than the lower limit VDDMIN. [0008] Since the conventional voltage detection circuit is constructed as described above, the above-mentioned small current value IO always flows through the circuit that generates the reference voltage. On the other hand, a large current corresponding to VDD-VSS always flows through the fifth and sixth resistors. Further, it is difficult to increase the resistance of the fifth and sixth resistors within the semiconductor chip because it requires a large area, and there is a problem that low power consumption cannot be achieved. The present invention has been made to solve the above-mentioned problems, and it is an object of the present invention to provide a voltage detection circuit that can be driven with low power consumption. Means for Solving the Problems The voltage detection circuit according to the present invention includes a voltage having a constant difference from a first or second potential, which is compared with the reference voltage, in a circuit for creating a reference voltage. A resistor is provided to generate the voltage, and a voltage having a constant difference between the reference voltage and the first or second potential is connected to the input of a voltage comparison circuit from the circuit for generating the reference voltage. [Operation] The voltage detection circuit according to the present invention is configured such that a voltage having a constant difference between the reference voltage and the first or second potential is supplied to both inputs of the voltage comparator circuit from a circuit that creates the reference voltage. By doing so, it is possible to reduce power consumption. Embodiment FIG. 1 shows the circuit configuration of a voltage detection circuit according to an embodiment of the present invention. In the figure, the first node 2 and the second
The first resistor 3 is connected between the nodes 4 and the other input B of the voltage comparison circuit 13 and the second node 4 are connected. 2
0a is a circuit that generates a voltage having a constant difference from a reference voltage and a first potential, and the other circuits are the same as the conventional example shown in FIG. Next, the operation will be explained. As in the conventional example, a current shown by equation (a) that does not depend on the change in VDD flows through the first PMOS1 and the second PMOS8, so the potential across the first resistor 3 also changes depending on the change in VDD. Not dependent. Therefore, the second node 4 has V as shown in FIG.
A voltage with a constant difference from DD is output. Voltage comparison circuit 1
3 compares the voltage V9 of the fourth node 9 and the voltage V4 of the second node 4. As described above, in this embodiment, the resistor 3 is provided in the reference voltage generating circuit 20 to generate a voltage with a constant difference from the first potential VDD to be compared with the reference voltage. The voltage generation circuit 20 is a circuit 20a that generates a voltage with a constant difference from the reference voltage and the first potential VDD, and both voltages are connected as inputs to the voltage comparison circuit 13, so that can be used to reduce power consumption. In the above embodiment, the second node 4 is used as a voltage with a constant difference from VDD;
The voltage V2 of the first node 2 as a voltage with a constant difference from D
Alternatively, the voltage V11 at the fifth node 11 may be used as a voltage with a constant difference between the voltage V7 at the third node and VSS. [0016] Furthermore, the first PMOS1, the second PMOS
A similar effect can be obtained by connecting the gate of NMOS 8 to the fourth node 9 and the gates of the first NMOS 5 and the second NMOS 12 to the second node 14. However, in this case, a voltage V2 having a constant difference from VSS is obtained from the first node 2, and a voltage V11 having a constant difference from VDD from the fifth node 11. [0017] As described above, according to the voltage detection circuit according to the present invention, the difference between the reference voltage and the first or second potential to be compared with the reference voltage is detected in the circuit for creating the reference voltage. A resistor is provided to generate a constant voltage, and a voltage with a constant difference between the reference voltage and the first or second potential is connected as the input of the voltage comparator circuit, so the node voltage in the circuit can be This has the effect of reducing power consumption.

[Brief explanation of the drawing]

FIG. 1 is a circuit configuration diagram showing the circuit configuration of a voltage detection circuit according to an embodiment of the present invention.

FIG. 2 is a circuit configuration diagram showing a circuit configuration of a voltage detection circuit according to a conventional example.

FIG. 3 is a voltage characteristic diagram showing the operation of a voltage detection circuit according to an embodiment of the present invention.

FIG. 4 is a voltage characteristic diagram showing the operation of a conventional voltage detection circuit.

[Explanation of symbols]

1 First PMOS transistor 2 First
Node 3 First resistor 4 Second node 5 First NMOS transistor 6 Second
Resistor 7 Third node 8 Second PMOS transistor 9 Fourth
Node 10 Third resistor 11 Fifth node 12 Second NMOS transistor 13 Voltage comparison circuit 14 Output 15 of voltage comparison circuit 13 Fourth resistor 16 Sixth node 17 Fifth resistor

Claims (1)

[Claims] 1. A first transistor of a first conductivity type connected between a first potential and a first node; a first transistor connected between the first node and a second node; resistor,
a first series circuit comprising a second transistor of a second conductivity type connected between a second node and a second potential;
a second resistor connected between the first potential and the third node; a second resistor connected between the third node and the fourth node, the gate of which is the gate of the first transistor; and a third transistor of the first conductivity type, which is connected to the first node or the fourth node, and whose absolute value of the threshold voltage is smaller than the absolute value of the threshold voltage of the first transistor. a third resistor connected between the fourth node and the fifth node; a third resistor connected between the fifth node and the second potential, the gate of which is the gate of the second transistor; and a second series circuit consisting of a fourth transistor of a second conductivity type connected to the fifth node or the second node; A voltage detection circuit comprising: a voltage comparison circuit that compares a reference voltage outputted from a reference voltage generation circuit with a voltage having a constant difference between the first potential or the second potential.