What does pfd mean?

Frequency and phase detector is a new phase detection circuit. It uses the jumping edge of the input signal to trigger the operation, and belongs to the edge-controlled digital frequency and phase detector. It can distinguish between phase and frequency. Because it only compares the transition edges of two input signals, there is no fixed requirement for the duty cycle of the input signals. Its excellent performance has been widely used in large and medium digital frequency synthesizers.

trait

1. During phase comparison, the rising edges of dclock and data must appear.

2. the pulse width of 2.dclock has nothing to do with the pulse width of data.

3. The phase detector will not lock the harmonics of the input data.

4. When the loop is locked, the output of the phase detector (up and down) is at a logic low level, which eliminates the fluctuation of the output signal of the loop filter.

5. The noise suppression ability of this phase detector is very poor. Noise will cause voltage fluctuation of data or data clock signal. Because of the poor noise suppression ability of this frequency discriminator, large voltage fluctuation will affect the output of the frequency discriminator.