Switched current interface circuit for capacitive micromachined accelerometer

Integrated silicon based sensor have many applications in fields as automotive, medical or process control. The development of smart sensors using low cost CMOS technologies requires not only adapt the sensor building process to the technology available but also modify the interface circuit to obtain good mixed analogue-digital readout circuits. A delta-sigma converter using switched current cells has been adapted to perform the interface of a differential capacitance sensor. The proposed interface architecture allows a sensor differential readout and it is insensitive to the stray capacitance influence. The acceleration sensor is CMOS compatible and it is based on a pendulum structure as common electrode, which has been obtained by bulk silicon micromachining and glass bonding. The experimental results obtained using 0.7 μm standard CMOS digital technology from ES2-Atmel, confirm the viability of the proposed interface circuit