A FREQUENCY SYNTHESIZER HAVING A PHASE-LOCKED LOOP WITH CIRCUIT FOR REDUCING POWER-ON SWITCHING TRANSIENTS

摘要

A phase-locked loop synthesizer (8) has a charge pump (9) and a loop filter (22) with a frequency preset capacitor (27). The synthesizer (8) has a transistor (34) of which one main electrode (36) is connected to the frequency preset capacitor. Another main electrode (35) of the transistor (34) is connected to a power-up terminal (32) that is also connected to the charge pump (21). Upon powering up, the transistor (34) causes the frequency preset capacitor (27) to quickly charge before a first pulse of the charge pump (21).