MPM7878 Digital Pressure Sensor

http://www.microsensor.cn Add: No.18, Yingda Road Baoji, P.R. China, Tel: +86 917 3600739/3600909

MPM7878 is a miniaturized Digital Barometric Air Pressure Sensor with a high accuracy and a low current consumption. It is both a pressure and a temperature sensor. The pressure sensor element is based on a capacitive sensing principle which guarantees a high precision during temperature changes. The small package makes the MPM7878 ideal for mobile applications and wearable devices. MPM7878‘s internal signal processor converts the output from the pressure and temperature sensor elements to 24-bit results. Each pressure sensor has been calibrated individually and contains calibration coefficients....

2 Test Condition Table 1: Test Condition http://www.microsensor.cn Add: No.18, Yingda Road Baoji, P.R. China, 721006 MICRO SENSOR CO.,LTD

Note: (©Key performance. 5 Operation MICRO SENSOR CO.,LTD http://www.microsensor.cn Add: No.18, Yingda Road Baoji, P.R. China, 721006

Operating Modes MPM7878 supports 3 different modes of operation: Standby, Command, and Background mode Standby Mode ——Default mode after power on or reset. No measurements are performed. ——All registers and compensation coefficients are accessible. Command Mode ——One temperature or pressure measurement is performed according to the selected precision. ——The sensor will return to Standby Mode when the measurement is finished, and the measurement result will be available in the data registers. Background Mode ——Pressure and/or temperature measurements are performed continuously according to the...

Sensor Interface MPM7878 can be accessed as a slave device through either SPI 3-wire, SPI 4-wire, or I2C serial interface. 5.3.1 ——The sensor's default interface. ——The sensor's address is 0x77(default) or 0x76 (if the SDO pin is pulled-down to GND) I2C write Writing is done by sending the slave address in write mode (RW=’0’), resulting in slave address 111011X0 (‘X’ is determined by state of SDO pin. Then the master sends pairs of register addresses and register data. The transaction is ended by a stop condition. Date byte Control byte Start Slave Address Register data - address 06h Date byte...

-The sensor will switch to SPI mode, if it detects an active low on the CSB pin. SPI 4-wire is the default SPI interface. -To enable SPI 3-wire configuration, a bit must be set in the Interrupt and FIFO configuration (CFG_REG) register after starting up. CSB is active low and has an integrated pull-up resistor. Data on SDA is latched by the device at SCK rising edge and SDO is changed at SCK falling edge. Communication starts when CSB goes to low and stops when CSB goes to high; during these transitions on CSB, SCK must be stable. Mode 3 (CPOL=1, CPHA=1) In SPI mode, only 7 bits of the register...

MICRO SENSOR CO.,LTD MPM7878 can generate an interrupt when a new measurement result is available and/or when the FIFO is full. The sensor uses the SDO pin for the interrupt signal, and interrupt is therefore not supported if the interface is 4-wire SPI. The interrupt is enabled and configured in the interrupt and FIFO configuration(CFG_REG) register. The SDO pin serves as both interrupt and as the least significant bit in the device address. If the SDO pin is pulled low the interrupt polarity must be set to active high and vice versa. The interrupt status can be read from the Interrupt Status...

MPM7878 Digital Pressure Sensor(V1.0) generate and interrupt if this has been enabled in the interrupt and FIFO configuration(CFG_reg) register. 5.6 Calibration and Measurement Compensation MPM7878 is a calibrated sensor and contains calibration coefficients. These are used in the application (for instance by the host processor) to compensate the measurement results for sensor non-linearity’s. The sections that follow, describe how to calculate the compensated results and convert them into Pa and °C values. 5.6.1 a) How to Calculate Compensated Pressure Values Read the calibration coefficients...

Table 4: Compensation Scale Factors 6.2 Application Circuit Example The example application circuit example uses the I2C serial interface. The SDO pin can be used for interrupt or to set least significant bit of the device address. MICRO SENSOR CO.,LTD http://www.microsensor.cn Add: No.18, Yingda Road Baoji, P.R. China, 721006

I2C Address 0x76(SDO pulled-down to GND) 0x77(SDO pulled-up to VDD or NC) Figure 1： Typical application circuit Table 6: Component Values Pull-up/down Resistor Supply Blocking Capacitor Note/Test Condition R2 is optional and will set the address to 0x76 instead of 0x77. The blocking capacitors should be placed as close to the package pins as possible. Calculating Absolute Altitude and Calculating Pressure at Sea Level With the measured pressure P and the pressure at sea level P0=1013.25hPa, the altitude in meters can be calculated with the international barometric formula: Thus, a pressure changes...

Altitude in standard atmosphere Barometric pressure [hPal With the measured pressure p and the absolute altitude the pressure at sea level can be calculated: Thus, a difference in altitude of Aaltitude = 10m corresponds to 1.2hPa pressure change at sea level. 7 Register Map Table 7: Register Map MICRO SENSOR CO.,LTD http://www.microsensor.cn Add: No.18, Yingda Road Baoji, P.R. China, 721006

MICRO SENSOR CO.,LTD http://www.microsensor.cn Add: No.18, Yingda Road Baoji, P.R. China, 721006

The lowest byte of the three bytes measured pressure value. PRS_B0 Address 02H Pressure (XLSB data) Reset value: 00H 8.2.3 TMP_B0 The lowestbyte of the three bytes measured temperature value. TMP_B0 Address: 04H MICRO SENSOR CO.,LTD http://www.microsensor.cn Add: No.18, Yingda Road Baoji, P.R. China, 721006

*) Note: Use in combination with a bit shift. See Interrupt and FIFO configuration(CFG_REG) register Table 8: Pressure measurement time(ms) and precision (Pa RMS) MICRO SENSOR CO.,LTD http://www.microsensor.cn Add: No.18, Yingda Road Baoji, P.R. China, 721006 Tel: +86 917 3600739/3600909 Fax: 3609977