A 64 Gb/s 1.5 pJ/bit PAM-4 Transmitter with 3-Tap FFE and Gm-Regulated Active-Feedback Driver in 28 nm CMOS

This paper presents a low-power implementation of a 64 Gb/s PAM-4 transmitter (TX) by using 3-tap feed-forward equalization (FFE) and G(m) -regulated active-feedback driver. The FFE tap generation is merged into serializer to minimize the overhead of FFE, by replacing a power-hungry delay generator. An active-feedback inverter based driver is also proposed to achieve a larger output swing compared with a resistive-feedback driver with limited output swing. The prototype chip is fabricated in 28nm CMOS technology and occupies 0.185 mm(2). The proposed TX achieves the data rate of 64 Gb/s while consuming 97.2 mW, which exhibits the state-of-the-art energy efficiency of 1.5 pJ/b.