Patent ID: 7414562

Claim:
An analog-to-digital converter (ADC) for generating a digital representation of an analog input signal, the ADC comprising a plurality of sub-ADCs cascading from a first stage to a last stage, each sub-ADC comprising a current comparator, having an analog current input adapted to receive an analog current signal, a reference current input adapted to receive a reference current signal, and an output configured to be a digital output of the sub-ADC; a subtractor, having a first input operatively coupled to the analog current signal, a second input operatively coupled to the reference current signal, and an output; an analog multiplexer, having a first input operatively coupled to the output of the subtractor, a second input operatively coupled to the analog current signal, a selector input operatively coupled to the output of the current comparator, and an output configured for analog current output generation of the sub-ADC; wherein the analog current signal at each sub-ADC except for the sub-ADC disposed at the first stage, is operatively coupled to the analog current output of an immediately preceding stage sub-ADC; and the plurality of sub-ADCs are configured to operate without synchronization with each other.