A two-chip accelerometer system has been designed, manufactured, and assembled in a standard dual-in-line plastic package. A capacitive sensing element is built on one chip and signal processing circuitry on a separate chip. The sensing element is designed in the form of a differential capacitor pair made from three highly doped polysilicon layers using surface micromachining technology. The circuitry is fabricated using a 1.75 ~tm CMOS technology and includes amplification, EPROM trim, filtering, and self-test functions. The system is designed for 50 g full scale acceleration, and operates in an open loop mode.
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IntroductionCurrent efforts to develop silicon-based accelerometers are driven by high volume applications in the automotive industry. These include ride control, inertial navigation, and crash sensing for airbag deployment. In each of these applications, reliability, self-diagnostics, and low cost are key requirements. Large-scale mechanical devices are not capable of meeting all these requirements. It is thus not surprising that the development of micromechanical accelerometers is one of the most aggressively pursued and challenging tasks in the sensor arena.To meet the challenge, designers have tried approaches based on piezoresistive [Tsugai and
The early effort of MEMS sensor development was focused mainly on the transducer: designing and manufacturing a mechanical device that could convert a physical input into an electrical signal using traditional semiconductor processes. With the rapid advancement in MEMS technologies, MEMS packaging is becoming increasingly critical and plays a major role in the successful commercialization of a MEMS product. Freescale has adopted the philosophy [1–2] of concurrent transducer and package designs to facilitate the rapid introduction of sensor products into the market. This paper presents a sub-modeling procedure that allows the modeling and simulation of a transducer and a package seamless at the same time.
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