Power Down Sim900B - SimCom SIM900B Hardware Design

The power on scenarios is illustrated as following figure.
VBAT
PWRKEY
(INPUT)
VDD_EXT
Serial Port
When power on procedure is completed, SIM900B will send following URC to indicate that the module is ready
to operate at fixed baud rate.
RDY
This URC does not appear when autobauding function is active.
Note: User can use AT command "AT+IPR=x" to set a fixed baud rate and save the configuration to non-volatile flash memory.
After the configuration is saved as fixed baud rate, the Code "RDY" should be received from the serial port every time when
SIM900B is powered on. For details, please refer to the chapter "AT+IPR" in document [1].
3.3.2

Power down SIM900B

SIM900B will be powered down in the following situations：
Normal power down procedure: power down SIM900B by the PWRKEY pin.
Normal power down procedure: power down SIM900B by AT command "AT+CPOWD=1".
Abnormal power down: over-voltage or under-voltage automatic power down.
Abnormal power down: over-temperature or under-temperature automatic power down.
SIM900B_Hardware Design_V2.01
Figure 6: Powered on/down module using transistor
Figure 7: Powered on/down module using button
Pulldown >1s
V < 0.9V
IL
13m
s
Undefined
Figure 8: Timing of power on module
Delay > 2.2s
V > 2.55V
IH
16
Smart Machine Smart Decision
Active
2012-05-07