Charge-pump phase-locked loop with DC current source

Details Charge-pump phase-locked loop with DC current source Charge-pump phase-locked loop with DC current source

1998-09-01

2000-03-21

Grimm, Siegfried H.

Oscillators

Automatic frequency stabilization using a phase or frequency...

Plural oscillators controlled

331 17, 331 25, 327157, H03L 707, H03L 7089, H03L 7093

Patent

active

060407425

ABSTRACT:
A phase-locked loop (PLL) has a phase detector (PD), a charge pump, a loop filter, and a voltage-controlled oscillator (VCO). The PD generates DOWN pulses based on differences in phase between an input signal and a feedback signal. The charge pump has an UP current source that generates a DC UP current and a DOWN current source that generates a DOWN current based on the DOWN pulses received from the phase detector. The charge pump generates a charge-pump current based on the DC UP current and the DOWN current. The loop filter receives the charge-pump current and generates a loop-filter voltage based on a net accumulation of charge from the charge-pump current. The VCO receives the loop-filter voltage and generates an output signal whose frequency is based on the loop-filter voltage, wherein the feedback signal is generated from the output signal. By using a DC UP current source, the PLLs of the present invention are able to operate at higher frequencies than conventional charge-pump PLLs, since the UP current source in the charge pump of a conventional PLL responds less quickly to PD pulses than does a conventional DOWN current source, due to mobility differences between holes and electrons, e.g., in conventional CMOS circuitry.

REFERENCES:
patent: 5166641 (1992-11-01), Davis et al.
patent: 5631587 (1997-05-01), Co et al.
patent: 5734301 (1998-03-01), Lee et al.
"A Self Correcting Clock Recovery Circuit," by Charles R. Hogge, Jr., IEEE Journal of Lightwave Technology, vol. LT-3, Dec. 1985, pp. 1312-1314.

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