A digital phase-based on-fly offset compensation method for decision feedback equalisers

A low-complexity method to reduce the offset voltage of dynamic comparators employed as samplers in decision feedback equalisers (DFE) is introduced. The authors propose the phase-domain offset reduction technique (PORT), which leverages an all-digital phase estimation of output data for offset compensation, without setting the comparator input to a common-mode voltage (V_CM). While traditional techniques might break the data link for offset adjustment, the proposed technique allows calibrating the comparator on-the-fly. Measurements from a 26-dB-loss on-chip emulated channel with chip-scope capability validates PORT through eye-diagrams at sampler input. A prototype was implemented in a TSMC 130 nm 1.2 V process, and experimental results show the possibility of extending PORT to state-of-the-art technology nodes for multi-gigabit operation.