Analysis of timing recovery for multi-Gbps PAM transceivers

The increasing data rates for many short distance (<1 m PCB) chip-to-chip links are exceeding the bandwidth limitation of the channel. With the sharp channel roll-off for many applications, pulse-amplitude modulation (PAM) has emerged as a means for improved channel efficiency. The modulation impacts both voltage and timing margins for the signal. Timing recovery in particular increases in complexity. This paper reviews various timing recovery methods for PAM signals and how the limited bandwidth affects the timing margin and timing recovery.