US 5,180,991 A · Frequency adjustable RC oscillator

Abstract

An RC oscillator for varying an oscillation frequency which has a counter for counting a clock pulse of the oscillation frequency and for outputting a counted value in a form of a plurality of bits to an output terminal. It also includes a standard capacitor, a plurality of capacitors having a capacitance value in proportion to a weight of bits outputted from the counter, and a plurality of switches connected to one end of each capacitor for selectively connecting the capacitors in parallel. A plurality of first gate circuits control the switches connected thereto in response to an output of the counter, each first gate circuit has an input terminal connected to an output terminal of the counter and an output terminal connected to a control terminal of the switches. A second gate circuit turns on the switches independently of the output of the counter in the case of a frequency adjustment of the oscillation signal, the second gate circuit has an input terminal connected to a predetermined output terminal of the counter and an output terminal connected to a switch for use of the standard capacitor.

Claims17

Dependent claims

An oscillator for generating an oscillator frequency from an oscillator output terminal thereof, comprising:

a binary counter for outputting an n-bit binary signal in response to the oscillator frequency generated from the oscillator output terminal, wherein n is a natural number, said binary counter further having n counter terminals consisting of a first counter terminal to an n-th counter terminal, an i-th terminal thereof outputting a first or second value corresponding to the i-th digit of the n-bit binary signal, wherein i is a natural number not greater than n;
and
an oscillation circuit cooperatively coupled to the binary counter, the oscillation circuit comprising
(i) a resistor having a predetermined resistance,
(ii) n capacitors consisting of a first capacitor to an n-th capacitor, an i-th capacitor having an i-th capacitance Ci determined by the equation Ci=Cn/(2.sup.n-i) wherein Cn is the capacitance of the n-th capacitor, and
(iii) n switching elements coupled to respective ones said n counter terminals consisting of a first switching element to an n-th switching element, an i-th switching element therein selectively coupling an i-th capacitor in circuit with said resistor in response to the first value being generated from the i-th counter terminal, whereby said oscillator can generate a regulated oscillator frequency from the oscillator output terminal defined by the oscillation circuit.

3 more elements

An oscillator for generating an oscillator frequency from an oscillator output terminal thereof, comprising:

a binary counter for outputting an n-bit binary signal in response to the oscillator frequency generated from the oscillator output terminal, wherein n is a natural number, said binary counter further having n counter terminals consisting of a first counter terminal to an n-th counter terminal, an i-th counter terminal therein outputting a first or second value corresponding to the i-th of a n-bit binary signal, wherein i is a natural number not greater than n;
and
an oscillation circuit cooperatively coupled to the binary counter, the oscillation circuit comprising
(i) a capacitor having a predetermined capacitance,
(ii) n resistors consisting of a first resistor to an n-th resistor, an i-th resistance Ri therein determined by the equation Ri=Rn/(2.sup.n-i) wherein Rn is the resistance of the n-th resistor, and
(iii) n switching elements respectively coupled to said n counter terminals consisting of a first switching element to an n-th switching element, an i-th switching element selectively coupling the i-th resistor in circuit with the capacitor in response to the first value being applied to the i-th counter terminal, whereby said oscillator can generate a regulated oscillator frequency from the oscillator output terminal defined by the oscillation circuit. PG,22

3 more elements

Dependencies are inferred from the claim text.

Frequency adjustable RC oscillator

Life of this patent

Frequency adjustable RC oscillator

Life of this patent

Abstract

Claims17