Fast frequency acquisition phase-frequency detectors for GSa/s phase-locked loops

This paper describes two techniques for designing phase-frequency detectors (PFDs) with higher operating frequencies (periods of less than 8x the delay of a fan-out-4 inverter (FO-4)) and faster frequency acquisition. Prototypes designed in 0.25-µm CMOS process exhibit operating frequencies of 1.25 GHz ( = 1/(8 ċ FO-4) ) and 1.5 GHz ( = 1/(6.7 ċ FO-4) ) for two techniques respectively whereas a conventional PFD operates < 1 GHz ( = 1/(10 ċ FO-4) ). The two proposed PFDs achieve a capture range of 1.7x and 1.2x the conventional design.