Understanding Smart Sensors - Nomads.usp

14 Understanding Smart Sensorstechnology to achieve a more sophisticated product solution. That may be in aprinted circuit board or ceramic substrate form. Figure 1.9 shows the steps thatcan be taken toward a higher level of monolithic integration.Figure 1.10 is an example of a level IV, two-chip smart sensor. The unituses the integrated pressure sensor showed in Figure 1.8, along with a singlechip8-bit MCU with an onboard A/D converter and an electrically erasableprogrammable read only memory (EEPROM) to achieve a minimumcomponent-countsmart sensor [9]. Except for three resistors used for increasedresolution, the other 10 components in the circuit are necessary for properfunctioning of the MCU. An undervoltage-sensing circuit is used for the resetfunction to provide an orderly powerdown in the case of low battery voltage.Two jumpers (and no potentiometers) are used for the initial calibration.The 01 code for the jumpers (J1 and J2) is used for zero calibration, and a 10code is used to indicate full-scale value. A 000 on the display indicates zero, andFFF indicates the full-scale value during calibration. Either the 00 or 11 code isused for normal operation. The values of zero and full scale are stored in theEEPROM. Three resistors are used to provide a ratiometric reference ofSensorelementModule solutionIntegratedamplifier and sensorModule solutionIntegratedsignal conditioningdata conversion and sensorModule solutionSensor and MCUFigure 1.9 Steps of development toward increased integration.