In this paper, we present a simple, compact and low-power interface for differential capacitive sensors with a direct digital output. The complete system is composed with a current to voltage converter, an integrator, a comparator and a one-bit digital to analog converter as a feedback. The so-obtained Sigma―Delta modulator is able to deliver directly a bit stream with a ratio of logical `1' directly proportional to the differential capacitance to be measured. A partially integrated prototype has been realized to demonstrate accuracy and non-linearity compatible with a 9-bit sensor.