JPH0797118B2 - Voltage detection circuit - Google Patents

Description

The present invention relates to a voltage detection circuit, and more particularly to a MIS type semiconductor integrated circuit using a semiconductor as a gate electrode.

[Conventional technology]

Conventionally, the circuit shown in FIG. 2 and the like have been used as a voltage detection circuit built in a semiconductor integrated circuit. Where MP21, MP22
Is a P-type MIS with equal current capability and threshold voltage
Transistors, MN21 and MN22, have the same current capacity, N-type MIS transistors having threshold voltages V _TN1 and V _TN2 respectively, 21 is a voltage dividing resistor using N-type MIS transistors, 22 is a comparator, V _DD is The power supply, V _SS, is the power supply. Here, Vref2 is a reference voltage, which is a voltage at which Vref2 = V _DD − (V _TN1 −V _TN2 ), and Vcmp2 is a voltage at which Vcmp2 = 1 / n · V _DD . Vcmp2 becomes Vref2 by the comparator
Determine if it is higher or lower.

Conventionally, such a circuit has been mainly used for detecting the battery life of an integrated circuit for a timepiece, so that the power supply voltage is relatively low (3v or less) and stable. Even if the sampling operation was performed, there was no problem because the response speed had no problem.

[Problems to be solved by the invention]

However, when used for a system reset signal of a micro computer system including a motor drive circuit or the like, neither of the above conditions can be satisfied. For example, in a battery-powered system, a power supply voltage fluctuates drastically due to a motor drive or the like during operation, and low power consumption is required during non-operation. Further, the power supply voltage is set to a relatively high voltage value (about 3 to 6v) because the motor is driven. Sampling operation cannot be performed to avoid system runaway, and current consumption is almost proportional to the square of the voltage when using a conventional circuit in a wide power supply voltage range (about 2 to 6v). It cannot be electricity. Further, the response speed of the N-type MIS transistor voltage dividing resistor used to reduce the area of the integrated circuit chip becomes slow when the current value is reduced.
Furthermore, the design is difficult because it has no linear characteristics.
Further, the partial pressure value also varies due to manufacturing variations.

The present invention is for solving such a problem, and an object thereof is to have a wide power supply voltage range, low power consumption, operate at high speed without sampling operation, and have a small occupied area in an integrated circuit. It is intended to provide a voltage detection circuit which is easy to manufacture, is resistant to manufacturing variations, and has small temperature dependence.

[Means for solving problems]

The voltage detection circuit of the present invention is a voltage detection circuit comprising a reference voltage source using a current mirror circuit and a comparator having a reference voltage as an output of the reference voltage source as an input, wherein the reference voltage source is A first transistor of a second conductivity type depletion type having a second conductivity type gate connected in series between a first power supply terminal and a second power supply terminal, and a first transistor having a first conductivity type gate And a second transistor of the second conductivity type having a second transistor of the conductivity type and a gate of the first conductivity type connected in series between the first power supply terminal and the second power supply terminal, and A fourth transistor of a first conductivity type having a gate of a first conductivity type, a gate and a source terminal of the first transistor are connected to the first power supply terminal, and the second and fourth transistors are connected. Transis Has a gate terminal connected to the drain terminals of the first and second transistors, a source terminal of the third transistor connected to the first power supply terminal, and a gate terminal of the third and fourth transistors. Is connected to the drain terminal of the third and fourth transistors, and outputs the reference voltage from a connection point of the drain terminals of the third and fourth transistors, and the comparator has a second conductivity type gate having a second conductivity type gate.
A differential input circuit including a conductive type fifth transistor and a second conductive type sixth transistor having a first conductive type gate; and a current source including a second conductive type seventh transistor The current source supplies a current based on the drain current of the first transistor to the source terminals of the fifth and sixth transistors, and the reference voltage of the fifth transistor is a differential amplifier circuit. It is characterized by being input to the gate terminal.

〔Example〕

 Hereinafter, the present invention will be described in detail based on examples.

FIG. 1 shows an embodiment of the voltage detection circuit of the present invention. 11
Is a reference voltage generating circuit, and 12 is a comparator. Unless otherwise specified, the gate electrode is polysilicon and the gate electrode type is N type. The reference voltage generating circuit includes a P-type gate P-type MIS transistor MP1 and a P-type MIS transistor (hereinafter referred to as PMIS) M having a current characteristic almost equal to that of MP1.
P2, N-type MIS transistor with the same current characteristics (hereinafter NMIS
Called) pair MN1 and MN2. The threshold voltage difference between MP1 and MP2 is the work function difference due to the difference in the gate electrode type, and is about 1.1v because the gate electrode is polysilicon. For example, assuming that the threshold voltage of MP2 is −0.5v, the threshold voltage of MP1 is 0.6v under the same manufacturing conditions, and a depletion type MIS transistor is obtained. Therefore, the circuit configuration shown in FIG. 1 is possible, and the output voltage Vref becomes VrefV _DD -1.1 [v] regardless of the threshold voltage. The measured temperature dependence of Vref is also in the ppm order, which is extremely small. Furthermore, the current consumption depends on the circuit configuration.
Determined by MP1 and almost independent of power supply voltage.
Further, in manufacturing, the P-type impurity ion implantation process for forming the source / drain regions of the PMIS can be used as it is, which is easy.

The comparator is composed of PMIS, MP4 which operates as a current source, MP5, MP6 and MN5, MN6 which constitute differential transistors. Here, MN5 and MN6 are NMIs having the same current characteristics.
S and MP6 are PMs with a threshold voltage of about -1.6v
IS and MP5 are P-type MIS transistors having the same current capability as MP6, with the gate type of MP6 being P-type. Again, based on the same principle as the reference voltage generation circuit, the offset voltage of the comparator is about the difference due to the work function difference of the gate electrode.
It becomes 1.1v. The temperature dependence of the offset voltage is also very small. Furthermore, the current consumption is determined by MP1 due to the circuit configuration,
Almost independent of power supply voltage. Also in manufacturing, the P-type gate is as easy as the reference voltage generating circuit, and -1.
The threshold voltage of about 6v is channel-doped with P-type impurities to bring the threshold voltage close to v.
It is easily obtained by masking the PMIS manufacturing process.

As described above, in this embodiment, since the circuit operating current is determined by the depletion MIS transistor MP1, the power consumption is low over a wide power supply voltage range, and the number of elements and the area occupied in the integrated circuit are small as compared with the conventional circuit, Manufacturing does not require a special process, and because it detects the potential difference determined by the physical work function, it is resistant to manufacturing variations and has low temperature dependence.
Since the response speed is determined only by the response speed of the comparator, it is possible to provide a high-speed and easy-to-design voltage detection circuit of about 2.2v.

Further, in the present embodiment, the work function difference between the P-type polysilicon gate and the N-type polysilicon gate is used, but it is of course possible to use various work function differences such as between different metals, between metal and semiconductor, between different semiconductors. Needless to say. Further, although the circuit diagram of this embodiment shows a power supply voltage detection circuit, it can be used for detection of other potentials, of course.

Furthermore, by using two stages of reference voltage source in series, about 3.3v
The voltage can be detected, and the detection voltage can be finely adjusted by using an intrinsic type gate or by channel doping.

Although the circuit configuration based on the V _DD potential is described in the present embodiment, the circuit configuration based on the V _SS potential may be used by using the circuit configuration in which PMIS and NMIS are reversed, or another potential may be used as the reference.

〔The invention's effect〕

As described above, according to the present invention, the power consumption is low over a wide power supply voltage range, the area occupied by the integrated circuit is small, the manufacturing is easy, the manufacturing variations are hardly affected, the temperature dependence is small, and the response is small. It is possible to provide a voltage detection circuit that is fast and easy to design.

[Brief description of drawings]

 FIG. 1 is a diagram showing an embodiment of a voltage detecting circuit of the present invention, FIG. 2 is a diagram showing an example of a conventional circuit, 11 is a reference voltage generating circuit 12, 12 are comparators MP1 to 6 are PMIS, and MN1 to 6 are NMIS.

Claims (1)

[Claims] 1. A voltage detection circuit comprising a reference voltage source using a current mirror circuit and a comparator having a reference voltage as an output of the reference voltage source as an input, wherein the reference voltage source is a first power supply. A second conductivity type depletion type first transistor having a second conductivity type gate connected in series between a terminal and a second power supply terminal, and a first conductivity type having a first conductivity type gate Second transistor, a second transistor of the second conductivity type having a gate of the first conductivity type connected in series between the first power supply terminal and the second power supply terminal, and a first conductivity type A fourth transistor of a first conductivity type having a gate of a second type, the gate and source terminals of the first transistor being connected to the first power supply terminal, and the gates of the second and fourth transistors end There is connected to the first and a drain terminal of the second transistor, a source terminal of said third transistor being connected to said first power supply terminal,
The gate terminal is connected to the drain terminals of the third and fourth transistors, the reference voltage is output from the connection point of the drain terminals of the third and fourth transistors, and the comparator is a second conductive element. Second with a gate of the mold
A differential input circuit including a conductive type fifth transistor and a second conductive type sixth transistor having a first conductive type gate; and a current source including a second conductive type seventh transistor The current source supplies a current based on the drain current of the first transistor to the source terminals of the fifth and sixth transistors, and the reference voltage of the fifth transistor is a differential amplifier circuit. A voltage detection circuit characterized by being inputted to a gate terminal.