Phase-locked loop having filter leakage cancellation circuit

Details Phase-locked loop having filter leakage cancellation circuit Phase-locked loop having filter leakage cancellation circuit

1996-08-15

1997-08-19

Chin, Stephen

Pulse or digital communications

Synchronizers

Phase displacement, slip or jitter correction

H03D 324

Patent

active

056595883

ABSTRACT:
A phase-locked loop includes a phase/frequency detector, a charge pump, a voltage-controlled oscillator and a frequency divider coupled together to form a feedback loop, the feedback loop having a filter node between the charge pump and the voltage-controlled oscillator for coupling to an off-chip loop filter. A first electrostatic discharge (ESD) protection device is coupled to the filter node, which has leakage path through which a leakage current flows. A filter leakage cancellation circuit is coupled to the filter node and includes a second ESD protection device which generates a reference current that is equal to the leakage current. The filter leakage cancellation circuit applies the reference current to the filter node such that the reference current is opposite to and cancels the leakage current.

REFERENCES:
patent: 4857866 (1989-08-01), Tateishi
patent: 5144156 (1992-09-01), Kawasaki
patent: 5539344 (1996-07-01), Hatakenaka

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