Coarse/fine A-D converter using ramp waveform to generate fine digital signal

Abstract

Analog-to-digital conversion in which a coarse digital representation of an input analog signal is converted to a coarse analog representation, and the difference between the original analog signal and the coarse analog representation is determined. A ramp waveform signal is generated, and a change in that waveform by an amount substantially equal to the difference between the original analog signal and the coarse analog representation is sensed. A plural bit fine digital signal corresponding to the sensed change of the ramp waveform is produced. The combination of the coarse and fine digital signals constitute the digital representation of the input analog signal. In one embodiment, the ramp waveform is increased until it is equal to the difference between the analog signal and the coarse analog representation, whereupon the ramp waveform is digitized. In another embodiment, the ramp waveform is used to reduce the level of a sample of the analog signal until that sample becomes equal to the coarse analog representation, at which time a counter that had been initiated at the commencement of sample reduction is stopped, the count being equal to the fine digital signal.

Dependencies are inferred from the claim text.