LPS25H Datasheet, PDF (11/45 Pages) STMicroelectronics – Embedded temperature compensation

LPS25H
3
Functionality
Functionality
The LPS25H is a high resolution, digital output pressure sensor packaged in a HCLGA
holed package. The complete device includes a sensing element based on a piezoresistive
Wheatstone bridge approach, and an IC interface able to take the information from the
sensing element to the external world, as a digital signal.
3.1
Sensing element
An ST proprietary process is used to obtain a mono-silicon µ-sized membrane for MEMS
pressure sensors, without requiring substrate to substrate bonding. When pressure is
applied, the membrane deflection induces an imbalance in the Wheatstone bridge
piezoresistances, whose output signal is converted by the IC interface.
Intrinsic mechanical stoppers prevent breakage in case of pressure overstress, ensuring
measurement repeatability.
The pressure inside the buried cavity under the membrane is constant and controlled by
process parameters.
3.2
IC interface
The complete measurement chain is composed by a low-noise amplifier which converts the
resistance unbalancing of the MEMS sensors (pressure and temperature) into an analog
voltage that is finally available to the user by 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 LPS25H 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 IC interface is factory calibrated at three temperatures and two pressures for sensitivity
and accuracy.
The trimming values are stored inside the device by a non-volatile structure. Whenever the
device is turned on, the trimming parameters are downloaded into the registers to be
employed during normal operation. This allows the user to employ the device without
requiring any further calibration.
3.4
FIFO
The LPS25H embeds FIFO register able to store 32 pressure output values, in order to
improve the system power saving, since the host processor does not need to continuously
poll data from the sensor, but it can wakeup only when requested and burst the significant
data out from the FIFO.
DocID023722 Rev 5
11/45
45