Ltx Corporation

Tim Alton

Michael Carlyle Davis

Wai-Kong Chen

Warren Necoechea

A phase-locked loop circuit having a programmable tuning voltage. As the input reference clock frequency is changed, the tuning voltage is changed accordingly to compensate for the propagation delay through the phase detector and thereby reduce discrepancies in the phase relationship between the input reference clock signal and the output clock signal at different frequencies. A set of compensation values corresponding to input reference clock frequencies are stored in a memory device. When the input reference clock frequency is changed, a corresponding compensation value is programmed to a digital-to-analog converter (DAC). The DAC outputs a voltage that is proportional to the value of the digital input to the DAC and can thus be used to regulate the tuning voltage of the PLL circuit so that the relationship of the input reference clock signal to the output clock signal remains stable with frequency changes.

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San Jose, CA, United States of America

Tim Alton