Patent ID: 7443206
Filing Date: 2008-10-28
Classification: H03D,H03L

Abstract:
1. A phase-frequency detector comprising: a first stage responsive to an edge transition location of a first periodic signal having a first period received on a first input node and to an edge transition location of a second periodic signal having a second period received on a second input node to drive a first output node with a first output signal and to drive a second output node with a second output signal, wherein the first stage comprises, a first sequential logic device coupled to the first input node and a second sequential logic device coupled to the second input node, and a first inverter coupled between an output node of the first sequential logic device and a data input node of the first sequential logic device and a second inverter coupled between an output node of the second sequential logic device and a data input node of the second sequential logic device; and a second stage responsive to an edge transition location of the first output signal and to an edge transition location of the second output signal to selectively drive a first output node of the phase-frequency detector with a first output pulse and to drive a second output node of the phase-frequency detector with a second output pulse, the first output pulse and the second output pulse each having a pulse width related to the edge transition location of the first periodic signal relative to the edge transition location of the second periodic signal, the second stage comprising a selector circuit to select between the first output node of the first stage and the second output node of the second stage, the second stage further comprising a first multiplexor and a second multiplexor responsive to the selector circuit to select between the first output node of the first stage and the second output node of the first stage, wherein each of the edge transition locations of the first and second periodic signals and each of the edge transition locations of the first and second output signals represent a point in time at which a related signal edge transition occurs.