SM5812 Amplified Pressure Sensor WITH ACCESS TO DIGITAL TEMPERATURE AND CORRECTED DIGITAL PRESSURE LOW-COST, FULLY AMPLIFIED, CALIBRATED, AND COMPENSATED IN A SINGLE PACKAGE AVAILABLE FOR DIFFERENTIAL, SINGLE-ENDED DIFFERENTIAL, GAGE & ABSOLUTE APPLICATIONS MULTIPLE PRESSURE RANGES AVAILABLE TO MEASURE PRESSURE DOWN TO 0.15 PSI FULL-SCALE AND UP TO 100 PSI FULL-SCALE DESCRIPTION The Silicon Microstructures SM5812 and SM5852 series of OEM pressure sensors combines state-of-the-art pressure sensor technology with CMOS digital signal processing technology to produce an amplified, fully conditioned, multi-order pressure and temperature compensated sensor in a dual in-line package (DIP) FEATURES configuration. Amplified, calibrated, fully signal Combining the pressure sensor with a conditioned output span of 4.0 VDC FS custom signal conditioning ASIC in a single (0.5 to 4.5 V signal) package simplifies the use of advanced Digital temperature and calibrated 2 silicon micromachined pressure sensors. pressure available through I C interface Now, the pressure sensor can be mounted Output ratiometric with supply voltage directly to a standard printed circuit board Multi-order correction for pressure non- and an amplified, high level, calibrated linearity (factory programmed) pressure signal can be acquired from the Multi-order correction for temperature digital interface or analog output. This coefficient of span and offset (factory eliminates the need of additional circuitry, programmed) such as a compensation network or micro- Gage, differential, and absolute versions controller containing a custom correction SMIs unique low-pressure die allows for algorithm. a full-scale pressure range of 0-0.15 PSI The SM5812/SM5852 Series pressure TYPICAL APPLICATIONS sensors are based on SMI s highly stable, piezoresistive pressure sensor chips Barometric measurement mounted on a ceramic substrate. An Medical instrumentation electronically programmable ASIC is Pneumatic control contained in the same package to provide Gas flow calibration and temperature compensation. Respirators and ventilators Heating, Ventilation and Air Conditioning The model SM5812 is designed for (HVAC) operating pressure ranges from 0-5 PSI up to 0-100 PSI. The model SM5852 is designed for operating pressure ranges from 0-0.15 PSI up to 0-3 PSI. For both models, the sensor output is ratiometric with the supply voltage. Rev 1.5 7 07 2005 - 2007 Silicon Microstructures, Inc. 1701 McCarthy Blvd. Milpitas, CA 95035 USA Tel: 408-577-0100 Fax: 408-577-0123 Sales Si-Micro.Com WWW.Si-Micro.Com SM5812 Amplified Pressure Sensor THEORY OF OPERATION coefficients. A combined total of twenty coefficients are available for correcting The operation of the signal processor is pressure and temperature non-linearity. The depicted in the block diagram below. The unique coefficients are determined during a external pressure sensor is a piezoresistive calibration process performed at the factory. bridge. This transduces the applied Factory calibration is the last step performed pressure into an electronic signal, which is which means the effect of the package on then inputted into the integrating amplifier of the pressure signal will also be taken into the ASIC. account. This provides a great advantage over conventional laser-trimming During the amplification step an offset approaches. correction factor is added in order to allow maximum gain for a given pressure while The DSP outputs a corrected digital word, minimizing the offset error. which travels to a 12-bit digital to analog converter (DAC) to provide a calibrated The signal is then passed to an 11-bit analog output. In addition to the analog analog to digital converter (ADC). The ADC output, the corrected pressure signal is samples the signal multiple times and uses 2 accessible through an I C digital interface. the sum of those samples as a 13-bit word. See SMI application note AN05-001 for a A digital signal processor (DSP) is then used detailed description of how to read out the to correct and calibrate the pressure signal. digital corrected pressure signal using the The DSP provides multi-order correction of I2C bus interface. both pressure and temperature non-linearity through the use of factory-programmed SMI Multi-Order Pressure and + 5 VDC Temperature Correction ASIC + 5 VDC Band-gap External Piezoresistive V Temp Bridge DSP (multi-order correction of 12-bit Switched MUX 11-bit ADC pressure and Sigma- Capacitor temperature Delta DAC Ground Integrateing non- Amplifier linearities) Analog Power-On EEPROM Output Analog Timing Reset Array Buffer Output Control Digital Timing 2 SDA 2 MHz I C Digital and Control Oscillator Interface Management SCL Analog Component Ground Digital Component Rev 1.5 7 07 2005 - 2007 Silicon Microstructures, Inc. 1701 McCarthy Blvd. Milpitas, CA 95035 USA Tel: 408-577-0100 Fax: 408-577-0123 Sales Si-Micro.Com WWW.Si-Micro.Com