The MC100EP140 is a three state phase frequency-detector intended for phase-locked loop applications which require a minimum amount of phase and frequency difference at lock. Since the part is designed with fully differential internal gates, the noise is reduced throughout the circuit, especially at high speeds. The basic operation of a Phase/Frequency Detector (PFD) is to "compare" an incoming signal (feedback) to a set reference signal. When the Reference (R) and Feedback (FB) inputs are unequal in frequency and/or phase, the differential UP (U) and DOWN (D) outputs will provide pulse streams which, when subtracted and integrated, provide an error voltage for control of a VCO. Detector states of operation are shown in the Figure 2 and the State Table.