3×16 Gb/s Compact Single-Ended PAM4 Transmitters With Inverter-Based Crosstalk Compensation for Memory Interfaces

A four-level pulse-amplitude modulation (PAM4) transmitter (TX) with crosstalk compensation (XTC) is proposed for short-reach memory interfaces. Simple encoders and transition detectors detect the data pattern causing crosstalk and appropriately activate inverter-based XTC taps. With gain and delay control of XTC, compensation error due to the mismatch between the victim and aggressor channels was minimized. The TX was fabricated in 28 nm LP CMOS and tested at 16 Gb/s. With XTC, the eye height and width were improved by 203% and 396%, respectively. Because it uses area-efficient inverter-based XTC taps, the TX occupies only 0.0067 mm2, achieving an area per data rate of 0.00042 mm2/Gbps.