Fully Integrated Low-Noise Readout Circuit with Automatic Offset Cancellation Loop for Capacitive Microsensors

Sensors

卷:15

Dong-il Dan Cho¹  Yunjong Park²  Hyungseup Kim²  Haryong Song²  Hyoungho Ko² 

[1] ASRI/ISRC, Department of Electrical Engineering and Computer Science, Seoul National University, Seoul 151-744, Korea;

[2] Department of Electronics, Chungnam National University, Daejeon 305-764, Korea;

关键词: capacitive sensing circuit;    automatic offset cancellation loop (AOCL);    correlated double sampling (CDS);    capacitive microsensor;   

DOI  :  10.3390/s151026009

来源: DOAJ

【 摘 要 】

Capacitive sensing schemes are widely used for various microsensors; however, such microsensors suffer from severe parasitic capacitance problems. This paper presents a fully integrated low-noise readout circuit with automatic offset cancellation loop (AOCL) for capacitive microsensors. The output offsets of the capacitive sensing chain due to the parasitic capacitances and process variations are automatically removed using AOCL. The AOCL generates electrically equivalent offset capacitance and enables charge-domain fine calibration using a 10-bit R-2R digital-to-analog converter, charge-transfer switches, and a charge-storing capacitor. The AOCL cancels the unwanted offset by binary-search algorithm based on 10-bit successive approximation register (SAR) logic. The chip is implemented using 0.18 μm complementary metal-oxide-semiconductor (CMOS) process with an active area of 1.76 mm2. The power consumption is 220 μW with 3.3 V supply. The input parasitic capacitances within the range of −250 fF to 250 fF can be cancelled out automatically, and the required calibration time is lower than 10 ms.

【 授权许可】

Unknown