LSM320HAY30 Datasheet, PDF (14/42 Pages) STMicroelectronics – MEMS motion sensor module: 3D digital accelerometer and 2D pitch and yaw analog gyroscope

Functionality and terminology
4
Functionality and terminology
LSM320HAY30
The LSM320HAY30 is an inertial module capable of detecting 3-axis linear acceleration and
2-axis angular rate. The system is housed in an LGA package.
The device includes an ASIC with a digital IC interface capable of providing linear
acceleration information through an I²C/SPI serial interface and analog output related to
angular rate.
The LSM320HAY30 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 used simultaneously on two different pins (INT1/INT2).
4.1
Factory calibration
The system is factory calibrated for sensitivity and zero level. The trimming values are
stored inside the device in non-volatile memory. When the device is turned on, the trimming
parameters are downloaded into the registers to be used during active operation. This
allows the use of the device without further calibration.
4.2
Sensitivity
Linear acceleration sensing
Liner Acceleration Sensitivity (LA_So) describes the gain of the sensor and can be
determined e.g. by applying 1 g acceleration to it. Because the sensor can measure DC
accelerations, this can be done easily by pointing the selected axis towards the ground,
noting the output value, rotating the sensor 180 degrees (pointing towards the sky) and
noting the output value again. By doing so, a ±1 g acceleration is applied to the sensor.
Subtracting the larger output value from the smaller one, and dividing the result by 2, leads
to the actual sensitivity of the sensor. This value changes very little over temperature and
over time. The sensitivity tolerance describes the range of sensitivities of a large number of
sensors.
Angular rate sensing
Angular rate detection produces a positive-going output voltage for counter-clockwise
rotation around the sensitive axis considered. Angular Rate Sensitivity (AR_So) describes
the gain of the sensor and can be determined by applying a defined angular rate to it. This
value changes very little over temperature and over time.
4.3
Zero level
Zero-g level
Zero-g level Offset (LA_TyOff) describes the deviation of an actual output signal from the
ideal output signal if no linear acceleration is present. A sensor in a steady state on a
horizontal surface will measure 0 g on both the X and Y axes, whereas the Z axis will
measure 1 g. Ideally, the output is in the middle of the dynamic range of the sensor (content
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Doc ID 16917 Rev 1