Terminology

LPY4150AL

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Doc ID 16581 Rev 1

4

Terminology

4.1

Sensitivity

An angular rate gyroscope is a device that produces a positive-going output voltage for

counterclockwise rotation around the sensitive axis considered. Sensitivity describes the

gain of the sensor and can be determined by applying a defined angular velocity to it. This

value changes very little over temperature and time.

4.2

Zero-rate level

Zero-rate level describes the actual output signal if there is no angular rate present. The

zero-rate level of precise MEMS sensors is, to some extent, a result of stress to the sensor

and therefore zero-rate level can slightly change after mounting the sensor onto a printed

circuit board or after exposing it to extensive mechanical stress. This value changes very

little over temperature and time.

4.3

Self-test

Self-test allows testing of the mechanical and electrical part of the sensor, allowing the

seismic mass to be moved by means of an electrostatic test-force. The self-test function is

off when the ST pin is connected to GND. When the ST pin is tied to Vdd, an actuation force

is applied to the sensor, emulating a definite Coriolis force. In this case the sensor output

exhibits a voltage change in its DC level which is also dependent on the supply voltage.

When ST is active, the device output level is given by the algebraic sum of the signals

produced by the velocity acting on the sensor and by the electrostatic test-force. If the output

signals change within the amplitude specified in

Table 3, then the mechanical element is

working properly and the parameters of the interface chip are within the defined

specifications.

4.4

High pass filter reset (HP)

The LPY4150AL provides the possibility to reset the optional external high-pass filter by

applying a high logic value to the HP pad. This procedure ensures faster response,

especially during overload conditions. Moreover, this operation is recommended each time

the device is powered.

4.5

Sleep mode, self-test and power-down

The LPY4150AL enables advanced power-saving features thanks to the availability of three

different operating modes. When the device is set in a Sleep mode configuration, the

reading chain is completely turned off, resulting in low power consumption. In this condition

the device turn-on time is significantly reduced, allowing simple external power cycling.

In accordance with the table below, the user can select the desired operating mode using

two dedicated pins (ST and SLEEP/PD).