Low-gain, low-jitter voltage controlled oscillator circuit

Details Low-gain, low-jitter voltage controlled oscillator circuit Low-gain, low-jitter voltage controlled oscillator circuit

1997-09-29

1999-09-14

Mis, David

Oscillators

Ring oscillators

331 34, 331177R, 331179, 331 10, 331 8, 327157, 375376, 455260, H03B 524, H03L 7099, H03L 718

Patent

active

059528923

ABSTRACT:
A low-gain, low-jitter VCO circuit implemented in CMOS provides center frequency adjustment to overcome process variations. Further, noise immunity is improved by using a separate feedback loop to provide the nominal current biasing for the oscillator chain. This feedback loop coarsely sets the center frequency. The actual control of the oscillation frequency is achieved by a second current source, whose output is added to the nominal bias current to provide a total bias to the oscillator. This second current source "fine tunes" the oscillator frequency responsive to a control signal. Because two separate current sources are used, the circuit can realize a high oscillation frequency with a low VCO gain. Another feature provides for adjusting the center frequency in response to a digital input word provided via external pins, or from internal logic or memory. The center frequency thus can be calibrated by measurement at the time of manufacture, or changes later by the end user or by other circuitry.

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Self, P.W.; "High SpeedPower Supply Independent CMOS Voltage Controlled Ring Oscillator with Level Shifting Circuit"; U.S. Ser. No. 843,703; original Fig. 2, Dec. 1992.

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