Over-Temperature Or Under-Temperature Power Down; Restart Sim900B By Pwrkey Pin - SimCom SIM900B Hardware Design

UNDER-VOLTAGE POWER DOWN
If the voltage > 4.8V, the following URC will be reported, and the module will be automatically powered down.
OVER-VOLTAGE POWER DOWN
At this moment, AT commands can not be executed any more, and only the RTC is still active. Power down mode
can also be indicated by STATUS pin, which is at low level at this time.
3.3.2.4

Over-temperature or Under-temperature Power down

The module will constantly monitor the temperature of the module,
If the temperature > +80℃, the following URC will be reported:
+CMTE: 1
If the temperature < -30℃, the following URC will be reported:
+CMTE:-1
If the temperature > +85℃, the following URC will be reported, and the module will be automatically powered
down.
+CMTE: 2
If the temperature < -40℃, the following URC will be reported, and the module will be automatically powered
down.
+CMTE:-2
At this moment, AT commands can not be executed any more, and only the RTC is still active. Power down mode
can also be indicated by STATUS pin, which is at low level at this time.
The AT command "AT+CMTE" could be used to read the temperature when the module is running.
For details please refer to document [1].
3.3.3

Restart SIM900B by PWRKEY Pin

When the module works normally, if the user wants to restart the module, follow the procedure below:
1) Power down the module.
2) Wait for at least 800mS after STATUS pin changed to low level.
3) Power on the module.
PWRKEY
（INPUT）
VDD_EXT
（OUTPUT）
SIM900B_Hardware Design_V2.01
Turn off
H
Figure 10: Timing of restart SIM900B
Delay > 800ms
Pull down the PWRKEY
to turn on the module
18
Smart Machine Smart Decision
Restart
2012-05-07