Receiver with threshold level finder

Abstract

An illustrative receiver includes: a decision element that derives symbol decisions from a slicer input signal; an equalizer that converts a receive signal into the slicer input signal; a summer that combines the symbol decisions with the slicer input signal to produce an error signal; and a level finder that operates on said signals to determine thresholds at which each signal has a given probability of exceeding the threshold. One illustrative level finder circuit includes: a gated comparator and an asymmetric accumulator. The gated comparator asserts a first or a second gated output signal to indicate when an input signal exceeds or falls below a threshold with a programmable condition being met. The asymmetric accumulator adapts the threshold using up steps for assertions of the first gated output signal and down steps for assertions of the second gated output signal, with the up-step size being different than the down-step size.