(RSS) Digitally controlled dual reference circuit
Original Publication Date: 2004-Aug-20
Included in the Prior Art Database: 2004-Aug-20
This article describes a circuit designed to control the upper and lower reference voltages on an analog to digital converter used to read serially shifted analog light intensity data from a contact image scanner. The analog data provided by the scanner is provided as a 0 to 0.7 volt value on a 1.5 to 1.9 volt DC offset. The high variability of the DC offset from scanner to scanner requires that the upper and lower references used by the Analog to Digital converter be adjustable. In essence the upper reference must always be 0.7 volts above the lower reference. The lower reference must adjust from 1.5VDC to 1.9VDC to compensate for the changing scanner output reference.