Figure 5: Turn On Gsm Part Using Driving Circuit - SimCom SIM548C HD V1.01 Hardware Design

SIM548C Hardware Design
Note:
Only enter AT command through serial port after the module is power on and Unsolicited
Result Code "RDY" is received from serial port. However if autobauding is set, the serial port
will receive nothing. The AT command can be set after 2-3s from the GSM part is power on.You
can use AT+IPR=x;&W 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 all the time when the GSM part is power on. Please refer to the
chapter AT+IPR in document [1].
3.4.1.1 Turn on the GSM part using the PWRKEY pin (Power on)
You can turn on the by driving the PWRKEY to a low level voltage for some
GSM part of the module
time and then release.This pin is pulled up to VBAT in the module. The maximum current that can
be drained from the PWRKEY pin is 0.4mA. The simple circuit illustrates as the following
figures.

Figure 5: Turn on GSM part using driving circuit

Figure 6 : Turn on GSM part using button
The power on scenarios illustrates as following figure.
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SIM548C_HD_V1.01 09.05.2008