Variable duty cycle window detecting analog to digital converter

Abstract

A high resolution analog to digital (A/D) converter amplifies and filters a magnitude difference between a pulse width modulated offset voltage and an input voltage to produce an amplified filtered difference voltage, the duty cycle of offset voltage modulation being adjusted such that the magnitude of the difference voltage is within a narrow input voltage range of a recirculating remainder A/D converter. The amplified, filtered difference voltage is converted to representative digital data by the recirculating remainder A/D converter. A microprocessor, which controls the offset voltage, combines the result with the magnitude of the offset voltage to produce a comparatively high resolution digital representation of the input voltage.