US Patent 7227488 Low-power CMOS image device with analog-to-digital converter circuit

Disclosed is a signal processing circuit which outputs a digital word corresponding to a current source controlled by a physical response. The signal processing circuit includes an analog integrated circuit for generating an analog signal in response to a time varying reference signal and a signal corresponding to the current source controlled by the physical response, a reference signal generator for generating a reference signal, a comparator for comparing the analog signal with the reference signal, an output circuit for generating the digital word indicating a time interval defined by a start signal and an end signal indicating a transition of an output of the comparator, and a controller inactivating the comparator in response to the end signal.