
xE922-3GR Hardware User Guide
1VV0301272
Rev.0.8 2017-01-05
Reproduction forbidden without written authorization from Telit Communications S.p.A. - All Rights
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Page 49 of 112
6.
Power ON/OFF and reset control
6.1.
Power On
Once power applied to the V_BAT, the power on can be triggered by four possible events:
·
ON_OFF key event (+ application of power to system with ‘first connect’ enabled)
·
External charger detection (CHG_POK)
·
RTC alarm
6.1.1.
ON_OFF key action
If the ON_OFF key is forced by external circuitry to V_RTC, the sytem startup procedure begins.
·
Active logic : HIGH
·
T_on minimum : 100msec
·
Debounce :15msec
When the system is supplied with V_BAT for the first time, it will automatically start up without waiting for
an event.
This so called ‘first connect’ power up condition can be disabled by adding a pulldown resistor on ON_OFF
signal of typical 10 kOhm.
Once the system is ON, if the ON_OFF key is forced to V_RTC for minium T_off > 10 seconds, the system
will switch OFF again.
After the initial startup procedure and when FW has booted, the ON_OFF key will be re-programmed to wake
up the system when asserted during sleep mode.