LIS3DETR datasheet(17/46 Pages) STMICROELECTRONICS

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LIS3DE

Terminology and functionality

3.4

IC interface

The complete measurement chain is made up of a low-noise capacitive amplifier which

converts the capacitive unbalancing of the MEMS sensor into an analog voltage using an

analog-to-digital converter.

The acceleration data may be accessed through an I2C/SPI interface, therefore making the

device particularly suitable for direct interfacing with a microcontroller.

The LIS3DE features a data-ready signal (DRDY) which indicates when a new set of

measured acceleration data is available, therefore simplifying data synchronization in the

digital system that uses the device.

The LIS3DE may also be configured to generate an inertial wakeup and free-fall interrupt

signal according to a programmed acceleration event along the enabled axes. Both free-fall

and wakeup can be available simultaneously on two different pins.

3.5

Factory calibration

The IC interface is factory calibrated for sensitivity (So) and Zero-g level (TyOff).

The trimming values are stored inside the device in non-volatile memory. Any time the

device is turned on, the trimming parameters are downloaded into the registers to be used

during the active operation. This allows the device to be used without further calibration.

3.6

FIFO

The LIS3DE contains a 32-level FIFO for each of the three output channels, X, Y and Z.

Buffered output allows 4 operation modes: FIFO, Stream, Stream-to-FIFO and Bypass.

Where FIFO Bypass mode is activated FIFO is not operating and remains empty. In FIFO

mode, data from acceleration detection on the X-, Y-, and Z-axis measurements are stored

in FIFO.

3.7

Auxiliary ADC

The LIS3DE contains an auxiliary 10-bit ADC with 3 separate dedicated inputs.

3.8

Temperature sensor

The LIS3DE is equipped with an internal temperature sensor. Temperature data can be

enabled by setting the TEMP_EN bit of theTEMP_CFG_REG (1Fh) register to “1”.

When the auxiliary ADC and temperature sensor are enabled, the third channel of the ADC

is used to digitize the temperature sensor output.

To retrieve the temperature sensor data, the BDU bit on CTRL_REG4 (23h) must be set to

“1”. Both the OUT_ADC3_H and OUT_ADC3_L registers must be read.

Temperature data is stored inside OUT_ADC3_H as two’s complement data, in 8-bit format,

left-justified.

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