A 95mw, 12fps, 3.2-Mpixel CMOS Imager with Nonlinear Response Programmable Gain Amplifier to Enlarge Dynamic Range

A digital color 3.2-Mpixel CMOS imager has been realized in a standard 0.18um CMOS technology. This chip has integrated with a proposed high dynamic range programmable gain amplifier using the nonlinear function to satisfy the human eye response. For reducing the noise level before analog-to-digital converter, a low noise 2-shared 2.25T pinned photodiode active pixel and a correlated double sample circuit have designed into the chip. The 3.2Mpixel CMOS imager has integrated with the row/column decoder, analog signal process, timing control and simple digital signal process, so that the sensor can be directly connected with a microprocessor or computer. The pinned photodiode active pixel achieves a conversion gain of 750uV/electron, 1.2mv voltage noise level and 72dB dynamic range under the 12 fps video rate, the dark condition and 27 degrees. Also, 0.3% peak-to-peak fixed pattern noise has obtained. The chip area is 28.69mm2 that produces 24 bit RGB video at 12 frames per second (fps) under the clock of 108MHz. Total power dissipation is less than 95mW from both 2.8V analog supply and 1.8V digital supply. The developed CMOS imager technology improves the performance of image to a level comparable to CCD so that the 3.2M-pixel CMOS image can be applied for 3G camera mobile phone.