A Capacitance-To-Digital Converter for MEMS Sensors for Smart Applications Articles uri icon

authors

  • PEREZ SANJURJO, JAVIER
  • PREFASI SEN, ENRIQUE JOSE
  • BUFFA, CESARE
  • GAGGL, RICHARD

publication date

  • June 2017

issue

  • 6

volume

  • 17

International Standard Serial Number (ISSN)

  • 1424-8220

abstract

  • The use of MEMS sensors has been increasing in recent years. To cover all the applications, many different readout circuits are needed. To reduce the cost and time to market, a generic capacitance-to-digital converter (CDC) seems to be the logical next step. This work presents a configurable CDC designed for capacitive MEMS sensors. The sensor is built with a bridge of MEMS, where some of them function with pressure. Then, the capacitive to digital conversion is realized using two steps. First, a switched-capacitor (SC) preamplifier is used to make the capacitive to voltage (C-V) conversion. Second, a self-oscillated noise-shaping integrating dual-slope (DS) converter is used to digitize this magnitude. The proposed converter uses time instead of amplitude resolution to generate a multibit digital output stream. In addition it performs noise shaping of the quantization error to reduce measurement time. This article shows the effectiveness of this method by measurements performed on a prototype, designed and fabricated using standard 0.13 mu m CMOS technology. Experimental measurements show that the CDC achieves a resolution of 17 bits, with an effective area of 0.317 mm(2), which means a pressure resolution of 1 Pa, while consuming 146 mu A from a 1.5 V power supply.

keywords

  • mems; cdc; pressure sensor; capacitive sensors; dual-slope; low power