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Typical Block Diagram of a MEMS Sensor A modern MEMS sensor gets built of three significant parts: MEMS sensing structure, application-specific integrat- ed circuit (ASIC), and sensor package. If capacitive or piezo-resistive technol- ogy is the basis for the sensing structure of the device, it detects the capaci- tance or resistance change or forces applied, respectively. The second part is the analog front-end of the sensor, and it includes a charge amplifier that converts the output of the mechanical sensing part into an analog output voltage. An embedded Analog to digital (A/D) converter digitizes this analog output into a digital format that will then get stored in dedicated inter- 12 ST/Industrial Sensing Solutions nal registers in the digital logic and available to be read by an external microcontroller. The third part is the digital logic that includes all the embedded filters, FIFO, configuration registers, and the digital interface to communicate with the external world (Figure 2). The package of the sensor provides the housing to the sensing and pro- cessing die. Shown below are some of the latest MEMS pressure sensors offered by STMicroelectronics (ST) (Figure 3, 5). The packaging technology of MEMS sensors has significantly improved over the years. The packaging solution for a sensor plays a critical role in the final performance and operation of the device because it plays a vital role in the stability of the sensor over temperature and time. The improvement in packaging technology for MEMS sensors have also helped sensor suppliers reduce the final price of these sensors. What type of packaging gets employed depends on the environment, in which the user operates the sensor. The block diagram illustrates a very high-level view of a typical MEMS sensor (e.g. a pressure sensor) offered by ST (Figure 4). Embedded Features The latest MEMS sensors have several features embedded within. The main advantages of these features include reducing the amount of the Figure 3: Cross-sectional view of a stacked packing of a MEMS pressure sensor. Figure 4: Internal block diagram of a conventional MEMS sensor. Figure 2: Block diagram of a digital output 3-axis accelerometer