A 20Gb/s Dual-Mode PAM4/NRZ Single-Ended Transmitter with RLM Compensation

In this paper, a 20Gb/s dual-mode four-level pulse amplitude modulation (PAM4)/non-return-to-zero (NRZ) single-ended voltage-mode transmitter is proposed. Its output drivers are composed of 60 basic source-series terminated (SST) driver units and 12 additional pull-up (PU) driver units. The additional PU driver units are used to reduce the eye height difference between four amplitude levels of PAM4. Implemented in 65nm CMOS technology, the active area of the transmitter is 0.06mm² including the clock buffer and IQ generator. It draws 61.5mW at 20Gb/s during PAM4 operation and 72mW at 10Gb/s during NRZ operation.