Area efficient, sequential gray code to thermometer code decoder

摘要

A Sequential Gray Code to Thermometer Code decoder circuit adapted for area efficient use at each pad of an integrated circuit chip for incrementally adjusting a digitally adjustable resistance for continuous or periodic adjustment of on-chip terminations. The sequential decoder for decoding a Gray code count to a T-bit Thermometer code count is constructed of a plurality (T) of cascaded decoder cells, each cell sensing the state of only one bit of the Gray code count. The decoder cells are cascaded to from decoding-latching stages each stage responsive to an individual one of single-bit changes between consecutive counts in the Gray code. Each stage contains a decoding-latching circuit adapted to detecting and latching the occurrence of one single-bit change in the Gray code.