Boosted CMOS APS Pixel Readout for Ultra Low-Voltage and Low-Power Operation

A new pixel readout technique is proposed for three-transistor (3T) CMOS active pixel sensor (APS) pixels. It utilizes the supply-boosting technique (SBT) in order to reduce power consumption and allow ultra low-voltage operation. The pixel supply voltage as well as the pixel reset and select signals were boosted to achieve wider and extended linear operating ranges. A CMOS image sensor containing a 54 × 50 array of 3T CMOS APS pixels was fabricated in a standard 2P3M 5-V 0.5- μm CMOS process to confirm the effectiveness of each boosting operation. Theory, simulation, and measurement results are presented. The boosting pixel supply voltage during pixel readout provides additional 31% dynamic range improvement on top of the seven times (7×) expansion attained by boosting the pixel reset signal. It was shown that the proposed boosted readout does not increase the number of transistors in the 3T CMOS APS pixels nor degrade the image quality.