Terminology LY3100ALH
8/13 Doc ID 16570 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 Sleep mode, self test and power down
The LY3100ALH 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).
Table 6. Sleep mode and Power-down mode configuration
Operating mode ST pin SLEEP/PD pin
Normal mode 0 0
Sleep mode 0 1
Self-test 1 0
Power-down 1 1
