LPS35HW Datasheet, PDF (13/48 Pages) STMicroelectronics – Embedded temperature compensation

LPS35HW
Functionality
3
Functionality
The LPS35HW is a high resolution, digital output pressure sensor packaged in an HLGA
full- mold package. The complete device includes a sensing element based on a
piezoresistive Wheatstone bridge approach, and an IC interface which communicates a
digital signal from the sensing element to the application.
3.1
Sensing element
An ST proprietary process is used to obtain a silicon membrane for MEMS pressure
sensors. When pressure is applied, the membrane deflection induces an imbalance in the
Wheatstone bridge piezoresistances whose output signal is converted by the IC interface.
3.2
IC interface
The complete measurement chain is composed of a low-noise amplifier which converts the
resistance unbalance of the MEMS sensors (pressure and temperature) into an analog
voltage using an analog-to-digital converter. The pressure and temperature data may be
accessed through an I²C/SPI interface thus making the device particularly suitable for direct
interfacing with a microcontroller. The LPS35HW features a Data-Ready signal which
indicates when a new set of measured pressure and temperature data are available, thus
simplifying data synchronization in the digital system that uses the device.
3.3
Factory calibration
The trimming values are stored inside the device in a non-volatile structure. When the
device is turned on, the trimming parameters are downloaded into the registers to be
employed during the normal operation which allows the device to be used without requiring
any further calibration.
3.4
How to interpret pressure readings
The pressure data are stored 3 registers: PRESS_OUT_H (2Ah), PRESS_OUT_L (29h),
and PRESS_OUT_XL (28h). The value is expressed as 2’s complement. To obtain the
pressure in hPa, take the two’s complement of the complete word and then divide by
4096LSB/hPa.
DocID029129 Rev 1
13/48