A current-mode, dual slope, integrated capacitance-to-pulse duration converter

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