how serdes‘ pma cdr works

A Serializer/Deserializer (SerDes) Physical Medium Attachment (PMA) Clock and Data Recovery (CDR) circuit is used to recover the clock and data from a serial data stream transmitted over a physical medium.

The PMA CDR circuit first receives the serial data stream and uses a phase detector to compare the phase of the incoming data with a local clock. The output of the phase detector is then filtered by a loop filter to generate a control signal for a voltage-controlled oscillator (VCO).

The VCO generates a clock signal that is synchronized with the incoming data, and this clock signal is used to sample the data and recover the original data stream. The recovered clock signal is also used to drive the phase detector, closing the loop and maintaining synchronization of the clock and data.

The PMA CDR circuit can operate at high data rates and is essential in modern high-speed communication systems such as optical fiber communication and high-speed Ethernet.