A 1 pF-to-10 nF Generic Capacitance-to-Digital Converter Using Zero-Crossing Delta Sigma Modulation

作者：Li, Bing; Wang, Wei; Liu, Jia; Liu, Wen-Jun; Yang, Qian; Ye, Wen-Bin^*

来源：IEEE TRANSACTIONS ON CIRCUITS AND SYSTEMS I-REGULAR PAPERS, 2018, 65(7): 2169-2182.

DOI：10.1109/TCSI.2017.2777872

• Calibration scheme
• capacitance-to-digital converter
• oversampled Delta Sigma modulation
• zero-crossing-based circuits

Conventional capacitance-to-digital converters (CDCs) suffer limitations either on narrow capacitance range or low resolution for jitter-induced noise and high power consumption. In order to avoid these limitations, a 13-b 1 pF-10 nF generic CDC is presented. In the proposed CDC with the oversampled Delta Sigma modulation, the zero-crossing-based circuits (ZCBCs) are used to replace the operational transconductance amplifier to avoid feedback loop stability issues. However, the ZCBCs inevitably incur the non-idealities and thus, a novel calibration scheme is presented for efficient non-ideality-error cancellation. In addition, for the purpose of making the proposed CDC sufficiently intelligent to adapt to a wide capacitance-sensing range, an adaptive auto-range mechanism is proposed. The above three techniques complement each other and work as a whole leading to the proposed CDC with wide range, high resolution, high linearity, and low power consumption. A prototype fabricated using 0.18-mu m CMOS technology is experimentally verified using a MEMS capacitive humidity sensor. The measurement results show that the CDC achieves a 13-b root-mean-square noise equivalent resolution with a 128-mu s conversion time and a 230 fJ/conversion-step figure of merit. The calibration scheme enhances the linearity from 7 to 11.4 b in the 1 pF-10 nF compatible capacitance range.

• 出版日期2018-7
• 单位深圳大学