Patent ID: 7061421

Claim:
A differential analog-to-digital data converter (ADC) for receiving a positive input signal and a negative input signal, comprising: a plurality of comparators each associated with a resolution bit of the data converter, one of the inputs of each of said comparators interfaced to a first analog input voltage and the other input of each of the comparators interfaced with a respective reference voltage; a resolution bit reference device for generating a plurality of successively increasing voltages at respective reference nodes from a first voltage to a second voltage, each of said reference nodes connected to a respective one of the other inputs of said comparators to provide the respective reference voltage, and the voltage difference between said reference nodes defining the resolution of the data converter; wherein for a substantially a zero difference between the positive and negative input signals, the voltage level of said first analog input voltage is disposed at a voltage above the voltage level on one of said reference nodes and below the voltage level on the next higher one of said reference nodes to constitute the zero code for the data converter; and a resolution varying device to vary the voltages between said respective nodes in a manner such that the zero code does not substantially vary.