Patent ID: 7667529

Claim:
A charge pump comprising: a voltage controlled oscillator (VCO) to produce a clock signal having a variable frequency in response to an error signal; a pump stage to produce an output voltage in response to the clock signal; a differential amplifier to produce the error signal in response to the output voltage and a reference voltage; and a bias circuit to bias the VCO by modifying a DC voltage component of the error signal, the bias circuit capable of commanding a lower nonzero VCO output frequency during a warm-up mode and a higher nonzero VCO frequency during a loading mode, wherein the bias circuit includes at least one diode-connected transistor to modify the DC voltage component of the error signal, the bias circuit further includes two diode-connected transistors and two switches to conditionally couple the two diode-connected transistors to an output node of the differential amplifier, and wherein the two switches are closed during the warm-up mode, and only one of the switches is closed during the loading mode.