Abstract
Charge-Based Capacitance Measurement (CBCM) technique is a simple but effective technique for measuring capacitance values down to the attofarad level. However, when adopted for fully on-chip implementation, this technique suffers output offset caused by mismatches and process variations. This paper introduces a novel method that compensates the offset of a fully integrated differential CBCM electronic front-end. After a detailed theoretical analysis of the differential CBCM topology, we present and discuss a modified architecture that compensates mismatches and increases robustness against mismatches and process variations. The proposed circuit has been simulated using a standard 130-nm technology and shows a sensitivity of 1.3 mV/aF and a 20× reduction of the standard deviation of the differential output voltage as compared to the traditional solution.
Highlights
Capacitive sensors are adopted in many fields, such as biological [2,3,4,5,6], gyroscopes [7,8], accelerometers, humidity sensors, and quality air for the detection of airborne particulate matter [9,10,11,12]
As compared to the traditional solution, the output voltage variation is reduced. This is due to the effect of the transistors implementing the switches of the scramblers and the dynamical element matching (DEM) circuit that cause a reduction of the charging current into the integrating capacitors
In this paper an automatic offset cancellation topology is proposed to improve the performance of the differential Charge-Based Capacitance Measurement (CBCM)
Summary
In [17,20], adjustable current mirrors are exploited, while in [19], a floating-gate trimming circuit is adopted 2021, 11, 22 through additional digital circuitry and human intervention This calibration step can be very long and tedious, especially for large arrays of capacitive electrodes, since it must be executed for each sensing capacitance. To overcome these limitations, in this paper we present a novel topology of differential. The solution exploits, for the first time in the literature, scramblers and dynamical element matching (DEM) to allow working without human intervention
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