Low-Power Digital Image Sensor for Still Picture Image Acquisition

摘要

This article presents the design and realization of a CMOS digital image sensor optimized for button-battery powered applications (limited available peak current and limited stored energy). First, a pixel with local analog memory was designed, allowing efficient sensor global shutter operation. The exposure time becomes independent on the readout speed and a lower readout frequency (reduced peak supply current) can be used without causing image distortion. Second, a multipath readout architecture was developed, allowing an efficient use of the power consumption in sub-sampling modes. These techniques were integrated in a 0.5 um CMOS digital image sensor with a resolution of 648 * 488 pixels. The peak supply current is 7 mA for a readout frequency of 4 Mpixel/s at Vdd = 3V. Die size is 55 mm2 and overall SNR is 55 dB. The global shutter performance was demonstrated by acquiring pictures of fast moving objects without observing any distortion, even at a low readout frequency of 4 MHz.