An adaptive 4-PAM decision-feedback equalizer for chip-to-chip signaling

This paper presents a 4-PAM adaptive decision-feedback equalizer (DFE) for chip-to-chip signaling. The DFE adapts to the channel impulse response by observing a calibration sequence sent across the channel. Uninterrupted signaling is maintained across a parallel bus by providing an additional channel and using multiplexors to reroute the signals of the channel being calibrated. Using the intermittent calibration sequence instead of the conventional LMS adaptation technique removes the need to generate an error signal, eliminating the associated analog blocks. Also presented is a novel method of using the DFE adaptation circuits to extract the system´s pulse response. The complete transceiver is implemented in a 0.18 μm CMOS process.