A Δ-Σ Capacitance-to-Digital Converter for Robot Flexible Electronic Skin

Inhalt:
To accurately measure the micro capacitance of capacitive tactile sensor, in this paper, a kind of capacitive sensor chip that uses second-order Σ-Δ modulation technique to realize the direct conversion of capacitance to digital signal is introduced, and it extends measurable capacitance range by compensation capacitor matrix. To minimize the error contribution of the CDC circuitry, precision circuit technique, such as chopping, is applied circuit level. Measurement results of the capacitive sensor realized in 0.18 µm CMOS technology show that the CDC achieves a capacitance range from 0 to 51.5pF. The circuit achieves a resolution of 167aF at a 15pF input capacitor, and the conversion time for one measurement is 13ms, during which the CDC consumes 201.6muA from a 1.8V single supply.