30.5 A 1.41pJ/b 56Gb/s PAM-4 Wireline Receiver Employing Enhanced Pattern Utilization CDR and Genetic Adaptation Algorithms in 7nm CMOS

Analog mixed-signal (AMS) receivers for 50+Gb/s PAM-4 offer lower power than ADC-DSP receivers [1]–[3]. Those using DFEs [2]–[3] suffer from relatively high power consumption due to the large number of latches needed in PAM-4 speculative DFEs. Better power efficiency can be achieved using only a CTLE [1]. However, analog front-ends (AFEs) are sensitive to variations in process, supply voltage and temperature. To combat this while accommodating links with loss exceeding 20dB, an AFE with extensive programmability is combined with an efficient genetic adaptation algorithm to select a setting that minimizes BER thus equalizing a 22dB-loss channel. The lack of a DFE, combined with a novel PAM-4 clock recovery scheme greatly reduces the number of latches required compared to previous works, resulting in 1.41pJ/bit power consumption in 7nm CMOS technology.