# US 4,377,781 A · Selectively adjustable voltage detection integrated circuit

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- Number: US 4,377,781 A
- Document ID: US4377781A
- Status: Granted
- Kind: A
- Application number: 06/150,485
- Filed: 1980-05-16
- Granted: 1983-03-22
- Earliest claimed: 1977-04-26
- Assignees: Kabushiki Kaisha Suwa Seikosha
- Inventors: Asakawa Tatsushi; Morozumi Shinji
- Web page: https://patentgrep.com/patent/US4377781A

## CPC

- G01R 19/16571: {comparing AC or DC current with one threshold, e.g. load current, over-current, surge current or fault current (G01R19/16514, G01R19/16519, G01R19/16528, G01R19/16533, G01R19/1659 take precedence; measuring currents by using elements sensitive to the magnetic field generated G01R15/14; measuring earth resistance G01R27/18; testing for leakage or short circuits in electrical apparatus G01R31/52)}
- G01R 35/005: {Calibrating; Standards or reference devices, e.g. voltage or resistance standards, "golden" references (G01R33/0035, G01R35/002 take precedence)}
- G04C 10/04: with means for indicating the condition of the power supply
- G04G 19/06: Regulation
- G05F 3/24: wherein the transistors are of the field-effect type only (G05F3/205, G05F3/26, G05F3/30 take precedence)
- H10D 84/83: of only insulated-gate FETs [IGFET]
- H10D 84/85: Complementary IGFETs, e.g. CMOS
- G01R: MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES (indicating correct tuning of resonant circuits H03J3/12)
- G04C: ELECTROMECHANICAL CLOCKS OR WATCHES
- G04G: ELECTRONIC TIME-PIECES
- G05F: SYSTEMS FOR REGULATING ELECTRIC OR MAGNETIC VARIABLES
- H10D: INORGANIC ELECTRIC SEMICONDUCTOR DEVICES

## Abstract

A voltage detection integrated circuit including a voltage regulation circuit for controlling the operation thereof is provided. The voltage detection integrated circuit includes a reference voltage circuit for producing a predetermined reference voltage, a voltage converter for converting a detected voltage for measurement and a comparator circuit for comparing the level of the reference voltage to the level of the converted voltage and for producing a comparison signal representative of the difference in voltage levels compared thereby. The voltage regulation circuit is coupled to the comparator circuit and the reference voltage circuit and/or voltage conversion circuit for selectively adjusting the level of the reference voltage produced by the reference voltage circuit and/or the converted voltage produced by the voltage converter, to thereby control the comparison signal produced by the comparator circuit.

## Claims

### Claim 1

In a voltage detection circuit, the improvement comprising a source voltage, a reference voltage circuit means for receiving said source voltage, said reference voltage circuit means including at least first and second pairs of complementary coupled P-channel and N-channel MOS transistors, said P-channel transistor in said first pair being coupled in series with said N-channel transistor in said first pair, said P-channel transistor in said second pair being coupled in series with said N-channel transistor in said second pair, at least one of said transistors in said first pair of complementary coupled P-channel and N-channel transistors having a different threshold voltage than the like polarity transistor in the second pair of complementary coupled P-channel and N-channel transistors, said reference voltage circuit means defining at least a first predetermined voltage having a magnitude that is related to the difference in threshold voltages between said respective like polarity transistors in said first and second pairs, said predetermined voltage being substantially independent of variations in temperature and minor variations in said source voltage, said reference voltage circuit means producing a set reference output voltage at said predetermined voltage in response to said source voltage.

### Claim 2 (depends on 1)

The voltage detection circuit as claimed in claim 1, wherein at least one of said P-channel and N-channel transistors in said first pair includes a first gate and a first drain, said first gate being coupled to said first drain.

### Claim 3 (depends on 2)

The voltage detection circuit as claimed in claim 2, wherein the other of said P-channel and N-channel transistors in said first pair includes a second gate, said transistor in said second pair which is of like polarity to said other transistor in said first pair having a third gate and a second drain, said second gate of said other transistor in said first pair and said third gate of said like polarity transistor in said second pair both being coupled to said second drain of said like polarity transistor in said second pair.

### Claim 4 (depends on 1)

The voltage detection circuit as claimed in claim 1, wherein said P-channel transistor in said first pair of transistors includes a gate and a drain, said gate being coupled to said drain, said N-channel transistor in said first pair having a gate, said N-channel transistor in said second pair of transistors including a gate and a drain, said gate of said N-channel transistor in said first pair and said gate of said N-channel transistor in said second pair being coupled to said drain of said N-channel transistor in said second pair of transistors.

### Claim 5 (depends on 1, 2, 3, 4)

The voltage detection circuit as claimed in claim 1, 2, 3 or 4, and including a voltage source adapted to deliver said source voltage, voltage converter means for producing a converted voltage representative of said source voltage delivered by said voltage source, and comparator means for receiving said set reference output voltage and said converted voltage and for providing a comparison signal in response thereto.

### Claim 6 (depends on 5)

The voltage detection circuit as claimed in claim 5, wherein each of said reference voltage means, voltage converter means and comparator means are comprised of integrated elements that are fabricated into the same metal oxide semiconductor integrated circuit chip.

### Claim 7 (depends on 5)

The voltage detection circuit as claimed in claim 5, wherein said voltage converter means includes a linear resistive network coupled to said voltage source for selectively dividing said source voltage into one of at least two distinct voltage levels defined by said resistive network.

### Claim 8 (depends on 7)

The voltage detection circuit as claimed in claim 7, wherein said resistive network is comprised of a plurality of integrated circuit resistive elements.

### Claim 9 (depends on 5)

The voltage detection circuit as claimed in claim 5, wherein said comparator means includes a current mirror defining an inverted input and a non-inverted input.

### Claim 10 (depends on 5)

The voltage detection circuit as claimed in claim 5, wherein said reference voltage means includes a voltage divider circuit for linearly converting said reference output voltage produced in response to the difference in threshold voltages between said respective like polarity transistors forming said reference voltage means.