SIM900D Hardware Design
V
IL
<1.2V
V
IH
> 2.6V
5s>Pulldown >1s
PWRKEY
(INPUT)
V
OH
< 0.1V
Delay > 1.7s
Logout net
STATUS
Figure9: Timing of turn off system using PWRKEY
3.4.2.2 Turn Off SIM900D Using AT Command
The SIM900D can use the AT command “AT+CPOWD=1” to turn off the module. This command lets the module
log off from the network and allows the module to enter into a secure state and save data before completely
disconnecting the power supply.
Before the completion of the switching off procedure the module will send out result code:
NORMAL POWER DOWN
After this moment, the AT commands can’t be executed. The module enters the POWER DOWN mode, only the
RTC is still active. POWER DOWN can also be indicated by STATUS pin, which is a low level voltage in this
mode.
Please refer to
document [1]
for detail about the AT command of “AT+CPOWD”.
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 will be automatic
shutdown soon.
If the voltage < 3.4V, the following URC will be presented:
UNDER-VOLTAGE POWER DOWN
If the voltage > 4.6V, the following URC will be presented:
OVER-VOLTAGE POWER DOWN
AT commands can't be executed. The module logs off from network and enters POWER DOWN mode, and only
the RTC is still active. POWER DOWN can also be indicated by STATUS pin, which is a low level voltage in
this mode.
3.4.2.4 Over-temperature or Under-temperature Automatic Shutdown
The module will constantly monitor the temperature of the module, if the temperature > +80 , the following
℃
SIM900D_HD_V1.02
09.04.2010
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