SIM800C ardware_Design_V1.02

SIM800C will be powered off in the following situations：
 Normal power off procedure: power off SIM800C by the PWRKEY pin.
 Normal power off procedure: power off SIM800C by AT command “AT+CPOWD=1”.
 Abnormal power off: over-voltage or under-voltage automatic power off.
 Abnormal power off: over-temperature or under-temperature automatic power off.