A High Dynamic-Range Readout Circuit with Differential Resistance-to-Time Conversion for Gas Sensor

This paper presents a high dynamic-range readout circuit with differential resistance-to-time conversion for resistive gas sensor. In traditional frequency output readout circuit, the charging-and-discharging circuit (CDC) and voltage window comparator (VWC) are used to convert the input current signal to output frequency. The output frequency is highly affected by the process variation of the charging capacitor in CDC. In this paper, the dual CDCs and VWCs are employed to cancel the error caused by the process variation of the charging capacitors. Thus, the detection range and the relative error could be improved. The proposed design is implemented with a 0.18 μm HV process. The core area is 333.2 × 321.815 μm
²
. The detection range is from 10 kΩ to 20 MΩ. The relative detection error is simulated to be 0.999937.