SimCom SIM8905A User Manual page 10

4 Crownpo
Power on/off
Power on
Users can power on SIM8905A by pulling down the PWRKEY pin for more than 2 second then release. This pin
is already pulled up to 1.8V internally, so external pull up is not necessary. Reference circuits are shown as below:
The power on sequence is illustrated in Figure9
VBAT
PWRKEY
LDO5_1V8
LDO6_1V8
Others
CDZ55C5V1SM
PWRKEY
4.7K
47K
Figure 7: Powered on/down module using transistor
PWRKEY
Figure 8: Powered on/down module using button
175ms
250us
Smart Machine Smart Decision
500mW
1.8V
R
1K
PMU
Module
1.8V
R
1K
PMU
Module
t>2s
Software Controlled
10
0805