A low-power-consumption 9bit 10MS/s pipeline ADC,used in a CMOS image sensor,is proposed. In the design, the decrease of power consumption is achieved by applying low-power-consumption and large-output-swing amplifiers with gain boost structure, and biasing all the cells with the same voltage bias source, which requires careful layout design and large capacitors. In addition,capacitor array DAC is also applied to reduce power consumption,and low threshold voltage MOS transistors are used to achieve a large signal processing range. The ADC was implemented in a 0.18μm 4M-1 P CMOS process,and the experimental results indicate that it consumes only 7mW, which is much less than general pipeline ADCs. The ADC was used in a 300000 pixels CMOS image sensor.
Noise and mismatch are important error sources in pipeline ADCs,so careful calculation and system simulation are carried out using Matlab software. To reduce power consumption while not lose performance, the amplifiers with the same structure are biased with one bias circuit, and a cascode compensation is adopted. A 10bit 50MS/s pipeline ADC, which can be used in CMOS image sensor systems with large pixel array,is designed and tested by using 0.35tzm 4M-2P CMOS process. According to test results, power consumption is only 42mW and SINAD is 45.69dB when sampling frequency is 50MHz. A balance between performance and power consumption is achieved.
