A Current-Mode, Dual Slope, Integrated Capacitance-to-Pulse Duration Converter

A capacitance-to-pulse duration converter, specifically for interfacing capacitive sensors, is presented. The principle is a double slope approach implemented using -based Miller integrators. The main strengths of proposed circuit are: 1) intrinsically small sensitivity to temperature; 2) simplicity of trimming offset and gain to correct the parameter spread; and 3) fast wake-up time. The circuit are analyzed in order to identify the elements responsible the residual temperature sensitivity and jitter on the duration. The effectiveness of the method is demonstrated by performed on a prototype, designed and fabricated the 0.35 m, 3.3 V Bipolar-CMOS-DMOS process BCD6 of STMicroelectronics.