Programmable driver/equalizer with alterable analog finite impulse response (FIR) filter having low intersymbol interference and constant peak amplitude independent of coefficient settings

摘要

A programmable driver/equalizer with an alterable FIR enables the equalization of serial links or other transmission systems to adapt to a variety of transmission media, specifically, intersymbol interference (ISI). Current mode differential drive circuits are coupled to a transmission media via a Finite Impulse Response (FIR) filter operating in the Z transform mode. The FIR filter includes A and B coefficient setting circuit, and is coupled to the drivers. The driver circuit also includes A coefficient level driver compensation and B coefficient level driver compensation to reduce self-induced ISI from the driver while the filter coefficients are activated. The coefficient setting circuit receive a combination of control bits to select the appropriate response for the driver to the various transmission media parameters. Adjustments to the driver output current are made at data run lengths exceeding certain values and subsequent adjustments are made for data run lengths exceeding larger values.