An Automatic Slope-Calibrated Ramp Generator for Single-Slope ADCs

Abstract

This paper presents a ramp generator with automatic slope calibration which is able to compensate slope deviation due to process and environmental effects. A novel analog feedback circuit is proposed to regulate the stop voltage in successive approximation while fix the start voltage of the ramp automatically without much calibration code input or complicated auxiliary circuits, which reduces the complexity of circuitry and timing, meanwhile, saves area and power. A 12-bit single-slope ADC (SS-ADC), employing the proposed ramp generator, has been implemented in a 0.11-µm CMOS process. The simulation results show that the offset of the ramp's stop voltage is reduced to 0.1 LSB and the nonlinearity of the ramp is 0.034%. Besides, the measurement results verify that this structure can fulfill automatic slope calibration.