Fast recovering charge pump for controlling a VCO in a low power

Details Fast recovering charge pump for controlling a VCO in a low power Fast recovering charge pump for controlling a VCO in a low power

1994-08-19

1996-06-04

Mis, David

Oscillators

Automatic frequency stabilization using a phase or frequency...

Afc with logic elements

331 8, 331 14, 331 17, 331173, H03L 300, H03L 708, H03L 7089, H03L 710

Patent

active

055237240

ABSTRACT:
A low power clocking circuit includes a crystal oscillator for generating a digital signal having a first frequency. The first frequency is relatively slow which allows the crystal oscillator to consume reduced power. The phase detector signal is coupled to control a charge pump circuit that generates a voltage on an output node for controlling a voltage controlled oscillator. The VCO generates a clock signal having a second frequency that is higher than the first frequency. The charge pump circuit includes an active mode and a power down mode and is operatively coupled between a first supply voltage and a second supply voltage. As typically provided, the charge pump includes a capacitor network coupled to the output node for maintaining the output voltage. The charge pump includes a voltage control circuit having an up input for increasing the output voltage and a down input for decreasing the output voltage. In addition, a ring enable input is provided for open circuiting all electrical paths from the first supply voltage to the second supply voltage and a precharge circuit is provided for maintaining the output voltage at a predetermined precharge level during the power down mode. Finally, a jump start input controls a jump start circuit for rapidly driving the output voltage to a predetermined level while the charge pump circuit transitions from a power down mode to an active mode. The jump start input includes a single pulse of the digital signal.

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