LSM320HAY30 datasheet(14/42 Pages) STMICROELECTRONICS

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Functionality and terminology

LSM320HAY30

14/42

Doc ID 16917 Rev 1

Functionality and terminology

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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