A distributed ramp signal generator of column-parallel single-slope ADCs for CMOS image sensors

抄録

This paper proposes a distributed ramp signal generator of column-parallel single-slope ADCs for CMOS image sensors. This architecture does not require any power-hungry amplifiers of the conventional one but consists of miniaturized column-wise ramp signal generators connected together by metal wires, which achieves high linearity and high uniformity. Simulation results show less than 1LSB nonlinear error of the ramp signal at 12-bit ADC resolution is attained only by having the consumption current of 6.4mA and the area of 2.4mm² which are much smaller than the conventional one. It is also confirmed that 100mΩ resistive connection attains less than 1LSB gain error mismatching, even though the mismatch of the column-wise ramp signal generators is as large as 20%.