Design And Implementation Of MEMS Microphone Readout Circuit

With the development of the consumer electronics products, the demand ofMEMS microphone is increasing, and the demand of its readout circuit is alsoincreasing. The performance of MEMS microphone readout circuit plays a vital rolein the performance of the whole microphone. Both foreign and domestics companiesare working hard in researching MEMS microphone readout circuit with low powerconsumption, low noise and low cost to gain the market share. This article designed aMEMS microphone readout circuit.The microphone readout circuit this article designed mainly includes the biasvoltage circuit and preamplifier circuit. This article analysed the structure of these twoparts and improved them. The bias voltage circuit focused on improving thetraditional structure of bandgap reference voltage circuit and charge pump circuit.Using temperature coefficient of resistance to reduce the temperature coefficient ofbandgap reference voltage circuit; using chopper technology to eliminate its mismatch.The charge pump circuit used a improved Latched charge pump. The new structurecan restrain the leakage current of Latched charge pump. The final stage of the chargepump added another clock to restrain the final leakage current to reduce the voltageripple. The core structure of the preamplifier is a source follower and its feedbackloop circuit to transform the signal. This part mainly improved the stabilizing chargecircuit; it used a structure of circuit to replace a large resistance which can beintegrated.This design used0.35μm BCD process of XFAB Company, using Spectre ofCadence to simulation. The design of the whole circuit had been finished, and thecircuit is taping-out. All the parameters of this circuit reach the design requiremets.