CMOS image sensor with testing circuit for verifying operation thereof

A CMOS image sensor having a pixel array to output analogue signals sensed from an object, the CMOS image sensor comprising:

• an analogue-to-digital converter including:
• a) a voltage generator for generating a first reference voltage;
• b) a comparison means for comparing the analogue signals with the reference voltage;
• and
• c) a storage means for storing digital signals in response to outputs form the comparison means;
• and
• a logic circuit for detecting whether the analogue-to-digital converter operates erroneously or not, wherein the logic circuit operates in response to test mode information stored in a mode register which the CMOS image sensor has, controls the voltage generator for the comparison means to receive a second reference voltage and a test voltage and stores in the storage means digital signals produced in response to a control signal from the comparison means, and wherein the storage means outputs the stored digital signals to an output terminal of the CMOS image sensor.