Offset Correction in Dual-Chopper Read-Out Circuits for Half-Bridge Capacitive Accelerometers

Conference: PRIME 2012 - 8th Conference on Ph.D. Research in Microelectronics & Electronics
06/12/2012 - 06/15/2012 at Aachen, Germany

Proceedings: PRIME 2012

Pages: 4Language: englishTyp: PDF

Personal VDE Members are entitled to a 10% discount on this title

Bergert, Jonas; Strache, Sebastian; Wunderlich, Ralf; Heinen, Stefan (Chair of Integrated Analog Circuits & RF Systems, RWTH Aachen University, 52062 Aachen, Germany)
Droste, Dirk (Robert Bosch GmbH, 72703 Reutlingen, Germany)

Sensor read-out circuits using half-bridge capacitive accelerometers suffer from a signal offset due to production mismatches. This paper describes a two-part solution to reduce the offset within the circuit to a minimum. A capacitor array is used to apply a coarse signal correction by placing digitally controlled capacitors in parallel to the sensor capacitors. The second part consists of a current DAC placed within a differential amplifier to balance out unsymmetric currents caused by the signal offset. A binary search algorithm is applied to determine the optimal configuration of both parts. The offset correction method was implemented to a dual-chopper read-out circuit and reduces the sensor offset to under 0.04 %.