An active charge-cancellation system for switched-capacitor sensor interface circuits

Interface circuits determine the performance of microsensors in growing automotive, medical, and process control applications. Currently available interface systems implement a capacitive measurement bridge in bipolar technology. Continued expansion of MEMS applications requires development of enhanced resolution interfaces in low-cost digital CMOS technology with switched capacitor (SC) methods. The active charge cancellation system (ACCS), an interface circuit architecture implemented in submicron CMOS, uses a feedback to directly sense and cancel the charge injected by MOSFET switch at the amplifier input. Unlike conventional methods that rely on component matching for charge injection compensation, the ACCS employs feedback compensation to provide more than two orders of magnitude reduction in charge injection error without requirement on component matching.