Terminology4
Sensitivity4.1
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.
Zero-rate level4.2
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.
Self-test4.3
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 the Mechanical characteristics table, then the mechanical
element is working properly and the parameters of the interface chip are within the defined
specifications.
Sleep mode, self-test and power-down4.4
The device enables advanced power-saving features thanks to the availability of three different
operating modes. In addition to standard normal mode and Power-down mode, 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).
Table 6: Sleep mode, self-test and power-down mode configuration
SLEEP/PD pinST pinOperating mode
00Normal mode
10Sleep mode
01Self-test
11Power-down
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LY330ALHTerminology
