Low voltage, low power RC oscillator circuit

Details Low voltage, low power RC oscillator circuit Low voltage, low power RC oscillator circuit

1981-12-24

1984-10-23

Westin, Edward P.

Oscillators

Solid state active element oscillator

Transistors

331108D, H03K 450

Patent

active

044790970

DESCRIPTION:

BRIEF SUMMARY
TECHNICAL FIELD

This invention relates to oscillators, and more particularly relates to an RC oscillator circuit operable at low voltage and low power requirements.


BACKGROUND ART

In the design of digital logic circuits, large scale integration techniques have brought about the construction of large numbers of components being fabricated on a single chip of silicon. In such circuitry, utilizing metal-oxide-semiconductor (MOS) techniques, random access memory devices as well as other semiconductor circuitry utilize numerous clock signals to provide a time base for such circuitry. Such clock signals are generated by oscillator circuits. Oscillator circuits find use in telecommunications integrated circuits, such as, for example, repertory dialers in which operation at low power and low voltage is essential.
A previously developed oscillator is shown in U.S. Pat. No. 4,205,279 issued to Beutler on May 27, 1980 and entitled "CMOS Low Current RC Oscillator". Such previously developed oscillators have not provided operating characteristics at sufficient low voltage and low power requirements. Additionally, such previously developed oscillators are sensitive to temperature and not completely independent of environmental temperatures.
A need has thus arisen for an RC oscillator for use in semiconductor circuitry which operates at low voltage and low power requirements. Further, a need has arisen for an RC oscillator that is less sensitive to temperature and supply voltage parameters. Additionally, a need has arisen for an RC oscillator that can be fabricated on a single CMOS semiconductor chip with improved reliability while being cost effective.


DISCLOSURE OF THE INVENTION

In accordance with the present invention, an RC oscillator is provided for fabrication on a CMOS semiconductor substrate which offers the advantages of low voltage and low power operating requirements and improved sensitivity to temperature and supply voltage parameters.
In accordance with the present invention, an RC oscillator circuit is provided which includes a voltage comparator circuit having first and second input terminals and an output terminal. The voltage comparator circuit generates an output signal at the output terminal. The RC oscillator circuit further includes a capacitor coupled to the first input terminal of the voltage comparator circuit. A voltage generator is coupled to the second input terminal of the voltage comparator circuit for generating a reference voltage for application to the voltage comparator circuit. A delay circuit is coupled to the output terminal of the voltage comparator circuit for delaying the output signal. A discharge device is coupled to the delay circuit and to the capacitor for discharging the capacitor, the discharge device being responsive to the output signal generated by the voltage comparator circuit. The RC oscillator circuit further includes a switch device coupled to the output terminal of the voltage comparator circuit and to the voltage generator. The switch device is responsive to the output signal of the voltage comparator circuit for controlling operation of the voltage generator, such that upon actuation of the switch device, the reference voltage is removed from the second input terminal of the voltage comparator circuit.


BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present invention and for further advantages thereof, reference will now be made to the following Detailed Description taken in conjunction with the accompanying Drawings in which:
FIG. 1 is a schematic circuit diagram of the RC oscillator circuit of the present invention;
FIG. 2 illustrates signal waveforms illustrating the operation of the present RC oscillator circuit; and
FIG. 3 is a schematic circuit diagram illustrating circuitry corresponding to the voltage comparator circuit illustrated in FIG. 1.


DETAILED DESCRIPTION

Referring to FIG. 1, the resistor-capacitor (RC) oscillator circuit of the present invention is illustrated and is generally identified by the numeral 10. RC

REFERENCES:
patent: 3742384 (1973-06-01), Breitzmann et al.
patent: 3904988 (1975-09-01), Hsiao
patent: 4205279 (1980-05-01), Beutler
patent: 4260959 (1981-04-01), Allgood
patent: 4264879 (1978-12-01), Duley
patent: 4365212 (1982-12-01), Gentile et al.

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