A 23.8-bit ENOB, ±5V Input Range Readout Circuit for High Precision Sensor Applications with 173.7dB-FoM

A 24-bit sensor Read-out Integrated Circuit (ROIC) with a ±5V input range is presented in this paper. The system utilizes a two-opamp programmable gain amplifier (PGA) and a third-order incremental switched-capacitor sigma-delta (SC Σ∆) analog-to-digital converter (ADC) to achieve a front-end gain ranging from 1 to 128. The PGA comprises a gain-boosting amplification stage and a class-AB output stage, effectively eliminating offset and 1/f noise through chopping. The ADC adapts a configurable zero optimization loop, allowing enhanced noise transfer function (NTF) at different output data rates (ODRs). Double-sampling technique is used to further improve the Signalto-Noise Ratio (SNR). This system is realized in 0.18µm standard CMOS process, providing three power modes and supporting up to four input signal channels. It exhibits a temperature coefficient of less than 2 ppm/°C over the operating range of -40 °C to 105 °C, while achieving a maximum Effective Resolution (ER) of 23.8 bits at a ODR of 10 samples per second (SPS). The calculated Figure of Merit (FoM) for the proposed ROIC reaches 173.7 dB.