Patent ID: 7324038

Claim:
An analog to digital converter (ADC) comprising: a first amplifier tracking an input voltage with its output; a coarse ADC amplifier connected to a coarse capacitor at its input and having a coarse ADC reset switch controlled by a first clock phase; a fine ADC amplifier connected to a fine capacitor at its input and having a fine ADC reset switch controlled by a second clock phase, wherein a set of reference voltages is selected for use by the fine ADC amplifier based on an output of the coarse ADC amplifier, wherein the coarse capacitor is charged to a coarse reference voltage during the first clock phase and connected to the first amplifier's output voltage during the second clock phase, and wherein the fine capacitor is connected to a fine reference voltage during the first clock phase and charged to the first amplifier's output voltage during the second clock phase; and an encoder that converts outputs of the coarse and fine ADC amplifiers to a digital output.