GSM/GPRS Module Series
M66 Hardware Design
M66_Hardware_Design Confidential / Released 28 / 80
Please refer to the
document [1]
for details about the AT command
AT+QPOWD
.
3.4.2.3. Under-voltage Automatic Shutdown
The module will constantly monitor the voltage applied on the VBAT, if the voltage is ≤3.5V, the following
URC will be presented:
UNDER_VOLTAGE WARNING
The normal input voltage range is from 3.3V to 4.6V. If the voltage is <3.3V, the module would
automatically shut down itself.
If the voltage is <3.3V, the following URC will be presented:
UNDER_VOLTAGE POWER DOWN
After that moment, no further AT commands can be executed. The module logs off from network and
enters power down mode, and only RTC is still active.
These unsolicited result codes do not appear when autobauding is active and DTE and DCE are not
correctly synchronized after start-up. The module is recommended to set to a fixed baud rate.
3.4.3. Restart
You can restart the module by driving the PWRKEY to a low level voltage for a certain time, which is
similar to the way of turning on module. In order to make the internal LDOs discharge completely after
turning off the module, it is recommended to delay about 500ms before restarting the module. The restart
timing is illustrated as the following figure.
PWRKEY
(INPUT)
VDD_EXT
(OUTPUT)
Turn off
Restart
Pull down the PWRKEY
to turn on the module
Delay >0.5s
Figure 10: Timing of Restarting System
NOTES
Quectel
Confidential
