Adaptation of PAM4 Serial Link Transceiver Equalizers using Eye Diagram Monitoring

Abstract

This paper studies the possible gains from using a single adaptation algorithm in tuning multiple equalizers in a Pulse Amplitude Modulation 4-level (PAM4) serial link transceiver. A comparison with the typical approach of using an algorithm for tuning one of the many equalizers used in transceivers from the perspective of bit error rate (BER) is carried out. This work also presents a method of measuring the eye diagram using an Eye Diagram Monitor (EDM) to continuously feed a Figure of Merit (FOM) to the adaptation algorithm to update equalizers’ settings. A demonstration on deploying our algorithm in adapting three major building blocks of a typical PAM4 transceiver is presented, showing its effectiveness in comparison with adapting only one equalizer at receiver (Rx) side. Simulation results show improvement in eye diagram measures in terms of achieving an eye height of 326 mV and a width of 97 ps compared to 67 mV and 12 ps respectively in case of adapting only one equalizer in Rx.