6.3 A Sub-250mW 1-to-56Gb/s Continuous-Range PAM-4 42.5dB IL ADC/DAC-Based Transceiver in 7nm FinFET

The enormous availability of data on the internet and the increased computational power available in the cloud require a constant increase in the bandwidth needed to transport data across the network. In order to mitigate the cost of infrastructure, the industry has proposed standards for 56Gb/s PAM-4 interfaces that can support legacy channels in conjunction with forward error correction (FEC) techniques. The reduced signal to noise ratio (SNR) available with PAM-4 modulation vs. NRZ requires sophisticated signal processing, making DSP-based solutions very attractive in terms of performance but, so far, at the expense of extra power vs. classical analog solutions. This paper demonstrates that this trade-off can be broken and presents a compact ADC/DAC DSP-based long-reach transceiver in 7nm FinFET technology that operates seamlessly from 3.5-to60Gb/s in PAM-4 (from 1-to-30Gb/s in NRZ mode) and consumes less than 250mW at 56Gb/s. The presented IP extends the deployment of DSP-based transceivers from repeater/re-timer applications to big ASICs with a very large number of ports.