A column readout channel for infrared and terahertz bolometers with direct analog to digital conversion

This paper describes a readout channel suitable for infrared and terahertz bolometric sensors arrays where the signal integration is performed simultaneously with the analog-to-digital conversion in a columnwise architecture. By exploiting the need of an integrator both in conventional IR readout channels and incremental converters, the proposed circuit implements a 5-bit continuous-time incremental conversion during signal integration, then the same electronics is used to perform an additional 6-bit algorithmic conversion on the integrator residual voltage. A prototype of the channel has been fabricated in standard CMOS technology (0.35μm 2P4M) featuring 11-bit digital output at 7.12ksamples/s and occupying an area of 0.0301mm² with a power consumption of only 90μW from a supply of 3.3V.