PHASE DETECTOR FOR HIGH SPEED CLOCK RECOVERY FROM RANDOM BINARY SIGNALS

摘要

An improved phase detector for use in a phase-locked loop. In one embodiment, the input data is first frequency divided into two signals. Two sets of three series connected latches each have the first latch receiving one of these divided data signals and each subsequent latch receiving the data output of the previous latch. The latches are enabled by alternate phases of the clock signal, where each consecutive latch has the opposite clock phase and corresponding latches from either set of three latches have identical clock phases. The clock phase of the seventh latch is opposite to that of either third latch. The data outputs of the second latches are inputs to a first XOR gate. The output of the first XOR gate is the input to a seventh latch whose output is the input to an eighth latch. The clock phase of the seventh latch is opposite to that of each third latch. The clock phase of the eighth latch is opposite to that of the seventh latch. A second XOR gate receives the data output of one third latch and the data input of its corresponding first latch. A third XOR gate receives the data output of the other third latch and the data input of its corresponding first latch. A fourth XOR gate receives the outputs of the first XOR gate and the data output of the seventh latch. A fifth XOR gate receives the output of the data output of the seventh latch and the data output of the eighth latch. The outputs of the second, third, fourth and fifth XOR gates control current sources, which when appropriately summed and integrated, provide a phase error signal. Delay means are also added to the circuit to compensate for the latch gate delays.