LPS25H datasheet(11/45 Pages) STMICROELECTRONICS

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LPS25H

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.

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