M20 Hardware Design
PWRKEY
（INPUT）
VDD_EXT
（OUTPUT）
V
IL
<0.3*VBAT
V
IH
>0.7*VBAT
1s >Pulldown >0.6s
Hiz
Logout net about 2s to 8s
Figure 8: Timing of turn off the module
3.4.2.2 Turn off module using AT command
Customer’s application can use an AT command “AT+QPOWD=1” to turn off the module. This
command will let the module to log off from the network and allow the software to save important
data before completely disconnecting the power supply, thus it is a safe way.
Before the completion of the power-down procedure the module sends out the result code shown
below:
NORMAL POWER DOWN
After this moment, no further AT command can be executed. And then the module enters the
POWER DOWN mode, only the RTC is still active. The POWER DOWN mode can also be
indicated by VDD_EXT pin, which is a low level voltage in this mode.
Please refer to document [1] for detail about the AT command of “AT+QPOWD”.
3.4.2.3 Over-voltage or under-voltage automatic shutdown
The module will constantly monitor the voltage applied on the VBAT, if the voltage 3.5V, the
following URC will be presented:
UNDER-VOLTAGE WARNNING
If the voltage 4.5V, the following URC will be presented:
OVER-VOLTAGE WARNNING
The uncritical voltage range is 3.4V to 4.6V. If the voltage 4.6V or 3.4V, the module would
automatically shutdown itself.
M20_HD_V1.01 - 30 -
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