A Research On Digital Control Circuit In MEMS Acceleration Servo Chip

MEMS acceleration sensor has the extensive application due to its excellentperformance. So its back-end servo circuit has become the focus in recent years.Having investigated MEMS difference capacitive acceleration sensor for oilexploration and seismic wave detection, MEMS acceleration servo chip with lowpower dissipation and good dynamic response is proposed.The key technology of the digital control circuit is described in detail, and thetest platform for digital function is developed. Top-Down design methodology isadopted in this design. This paper focuses on Verilog HDL coding, functionsimulation, FPGA verification, post-layout simulation and digital function test of chip.The digital control circuit includes of IIC Slave, MPCG(Multiphase ClockGeneration), BSCA(Bit Stream Counting Average) and OD(Overload Detection).They provides communication between the chip and system, control of analogcircuit’s working phase, data detection and processing.An improved IIC slave circuit is presented in the paper. It emphasizes thattraditional state machine in a slave IIC bus has been predigested, and improved statemachine is obtained. The synthesization results show that, slave with improved statemachine is better than the one with traditional state machine, for area being about20％reduced and power disposing about4％. Meanwhile, an easy and efficientmethod of FPGA(Field Programmable Gate Array) verification has been adopted tovalidate the IIC Slave circuit.The12various switches in analog circuit are controlled by MPCG. So front-endcircuit can orderly work in sensing phase, sampling and holding phase, forcing phase,and calibration phase. The digital control circuit operates at the clock frequency of4.096MHz, and a whole working cycle of12switches is composed of32main clockcycles.BSCA calculates the average of bit stream from LC(Latch Compare). ODdetects a long series consecutive1s or0s of bit stream from LC.