A 8Gb/s PAM-4/NRZ Dual-Mode Transmitter for Panel Interfaces with Run-length Limited Maximum Transition

This paper presents a 8Gb/s four-level pulse amplitude modulation (PAM-4) /non-return-to-zero (NRZ) dual-mode transmitter. The transmitter implements a 8B/5S PAM-4 run-length limited maximum transition avoidance (RLL-MTA) encoding method for panel interfaces. RLL-MTA encoding eliminates maximum transitions and restricts run-length to 4 to reduce DC wander in PAM-4 signaling, which is employed in the clock data recovery (CDR) used on the receiver. The transmitter utilizes a 4-tap feedforward equalizer (FFE) for NRZ and a 2-tap FFE for PAM-4. Implemented in 28nm CMOS technology, the transmitter occupies a 0.0506mm² active area and exhibits power efficiency, with 2.17pJ/b for PAM-4 and 3.23pJ/b for NRZ.