PCML driver for LVDS receiver loads

摘要

The improved PCML communications driver corrects current loss and reduced voltage swing when driving an LVDS receiver load by reducing the value of the Rt 1 resistors. By changing the value of the two Rt 1 resistors from Rt 1 to Rt 1/2 (or lower), the full bias current can be restored and voltage swing is substantially improved. By making Rt 1 a programmable resistor so Rt=Rt 1/2 for DC bias calculation, Q 2 bias current is increased back to IB, instead of IB/2.