Full-rate switched capacitor multi-tap DFE for long-tail post-cursor cancellation

Decision feedback equalizer (DFE) is commonly used in the receiver to cancel out the inter-symbol interference (ISI). However, the capacitive loading at the analog summing node increases with addition of each post-cursor cancellation tap, which directly impacts the bandwidth. In this paper, we propose a multi-tap switched-capacitor (SC) topology which can cancel out multiple post-cursor content with reduced loading at the analog summing node. Simulation has been implemented in UMC65-nm SP technology for a 4-tap system, using a triple cascaded B12” channel, having attenuation of 19 dB at nyquist frequency of 2 GHz. Improvements in eye height up to 84% is observed for the eye diagram at the summing node with 4-tap cancellation compared to 1-tap cancellation.