Solid-state image-pickup device, camera system, and method for driving same

A camera system having a plurality of pixels, each converting an incident-light quantity into a respective electrical signal, the camera system further having a plurality of analog-to-digital converters that each converts an analog signal obtained from a respective one of the pixels into a digital signal,

• wherein, each analog-to-digital converter includes:
• an output having a plurality of bits;
• a plurality of comparators, wherein each of the comparators compares a respective one of a plurality of reference voltages changing over time to the analog signal from the same one of the pixels, and at least first and second reference voltages are transmitted to respective ones of the comparators.

A method of driving a camera system having a plurality of pixels, each converting an incident-light quantity into a respective electrical signal, the camera system further having a plurality of analog-to-digital converters that each converts an analog signal obtained from a respective one of the pixels into a digital signal, each analog-to-digital converter including an output having a plurality of bits, the method comprising the steps of:

• transmitting a respective one of a plurality of reference voltages to each of the comparators of one of the analog-to-digital converters, each reference voltage being different from each other;
• comparing a first of the different reference voltages changing over time to the analog signal from the respective one of the pixels by using a first comparator of the one analog-to-digital converter;
• comparing a second of the different reference voltages changing over time to the analog signal from the same respective one of the pixels by using the a second comparator of the one analog-to-digital converter.