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Figure 9: The minimal VBAT voltage requirement at VBAT drop
Note: Hardware power down voltage is 3.0V.
4.1.2. Monitoring Power Supply
AT command “AT+CBC” can be used to monitor the VBAT voltage. For detail, please
refer to document [1].
4.2. Power on/off Scenarios
4.2.1. Power on SIM800H&SIM800L
Customer can power on SIM800H&SIM800L by pulling down the PWRKEY pin for at least 1 second and
release. This pin is already pulled up to VBAT in the module internal, so external pull up is not necessary.
Reference circuit is shown as below.
SIM800H&SIM800L_Hardware Design_V2.02 22
2015-07-27
4.7K
47K
Turn on/off
impulse
PWRKEY
VBAT
100K
Power
on/down logic
1K
Module
Figure 10:
Powered on/off module using transistor
PWRKEY
VBAT
100K
Power
on/down logic
1K
Module
Figure 11: Powered on/off module using button
The power on timing is illustrated as in the following figure.
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Figure 12: Timing of power on module
When power on procedure is completed, SIM800H&SIM800L 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: Customer can use AT command “AT+IPR=x” to set a fixed baud rate and save the configuration to non-volatile flash
