A 28Gb/s NRZ and 56Gb/s PAM4 SerDes Dual-Mode Transmitters Based on 28nm CMOS

This paper designs a dual-mode transmitter that supports non-return to-zero modulation (NRZ) at a rate of 28 Gb/s and four-level pulse amplitude modulation (PAM4) at a rate of 56Gb/s, using CMOS 28nm process. The transmitter uses a 4:1MUX with a 1/2 speed architecture to reduce the transmitter area. CML2CMOS circuit is used to convert the signal into a full swing signal. The design of the clock buffer circuit improves the driving ability. The output 56Gb/s PAM4 call consumes 265mW and the energy efficiency is 4.7pJ/bit. The 28GB /s NRZ signal consumes 215mW and the energy efficiency is 7.6pJ/bit.