A Current Calibration Circuit for a 14-Bit Column-Parallel Dual-Ramp Single-Slope ADC in Infrared Image Sensors

This brief introduces a current calibration circuit that is specifically designed for use in a column-parallel Dual-Ramp Single-Slope (DRSS) ADC. This circuit creates two current sources with a precise current ratio. These currents are then used in coarse and fine conversion stages. The desired current ratio can be achieved by adjusting the integration times based on standard clock sources in typical CMOS circuits. A 14-bit DRSS ADC that utilizes this calibration technique has been implemented in a $0.18~\mu $ m CMOS technology to be used in an Infrared Detector (IR) Read-Out Integrated Circuit (ROIC). Experiments demonstrate that a DNL error smaller than ±0.4 LSB is successfully achieved when the current calibration circuit is active.