Fibocom L831-EAU-01 - Software Shutdown; Hardware Shutdown

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L831-EAU-01 Hardware User Manual Page
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3.3.2.1 Software Shutdown
When the module receives the software shutdown command (AT+CPWROFF), the module will start the
finalization process (the reverse process of initialization), and it will be completed after 3s. In the
finalization process, the module will save the network, SIM card and some other parameters from memory,
then clear the memory and PMU will be powered off. After shutdown, the VSD2_1V8 voltage is also shut
down. The software control timing is shown in Figure 3-7:
Figure 3-7 Software Shutdown Timing Control
After the software shutdown, the FUL_CARD_POWER_OFF # pin will remain high which prevents the
module from restarting again. To enable the next restart, the FUL_CARD_POWER_OFF# pin should be
pulled low after shutting down more than 500ms (recommended1000ms).
Note:
The VSD2_1V8 signal is the internal PMU 1.8V output voltage which is not connected to the M.2
interface. The above timing of VSD2_1V8 is only for reference.
3.3.2.2 Hardware Shutdown
By pulling down RESET for 1ms first and then FULL_CARD_POWER_OFF# (or controlling M.2 3.3V
power by GPIO) for more than 500ms (1,000 ms recommended), the Power Management Unit (PMU) of
the module loses its power, and then the module will shut down by hardware. As the PMU of the module
loses its power when FULL_CARD_POWER_OFF# is pulled down, the module may be damaged after
repeated reboots.

The power-off timing diagram of hardware controlling 3.3V power is shown in Figure 3-8;
 The power-off timing diagram of hardware controlling FULL_CARD_POWER_OFF# is shown in
Figure 3-9;