A 2.5-48 Gb/s 16.6 ns Turn-On Time NRZ/PAM4 Pulse-Based Rapid-On/Off Baud-Rate CDR for Mobile Interfaces

This brief presents an NRZ/PAM4 rapid-on/off baud-rate clock and data recovery (CDR) for mobile interfaces, featuring power-efficient bandwidth scaling. To minimize power overhead due to large turn-on time, a pulse-based rapid clock recovery method is proposed. This method estimates and immediately compensates for initial phase error based on a pre-trained look-up table, significantly reducing the CDR’s turn-on time. In addition, a background PAM4 eye-climbing algorithm (ECA) addresses the sub-optimal lock point issue of conventional baud-rate phase detectors by adjusting the lock point to maximize the vertical eye margin (VEM). The prototype receiver fabricated in a 28 nm CMOS supports data rates from 2.5 to 48Gb/s, accommodating both legacy and next-generation mobile interfaces. It achieves an energy efficiency of 1.43 pJ/b at 48 Gb/s while demonstrating a fast turn-on time of 16.6 ns, enabling superior energy efficiency across various effective data rates. Moreover, the PAM4 ECA increases VEM of the PAM4 middle eye by 18 mV, ensuring error-free operation.