Wake Up Sim800L From Sleep Mode 2; Rtc Backup - SimCom SIM800L Hardware Design

4.3.5.

Wake Up SIM800L from Sleep Mode 2

When SIM800L is in sleep mode 2 (AT+CSCLK=2), the following methods can wake up the module:
Send data to SIM800L via main serial port (the first character will lose).

Receive a voice or data call from network.

Receive a SMS from network.

Note: Autobauding is default. It cannot enter sleep mode in the absence of synchronous serial port baud rate after module power
on.

4.4. RTC Backup

Current input for RTC when the VBAT is not supplied for the system. Current output for backup battery when
the VBAT power supply is in present and the backup battery is in low voltage state. The RTC power supply of
module can be provided by an external capacitor or a battery (non-chargeable or rechargeable) through the VRTC.
The following figures show various reference circuits for RTC back up.
External capacitor backup

Non-chargeable battery backup

Rechargeable battery backup

SIM800L(MT6261)_Hardware Design_V1.01
Large-capacitance
Capacitor
Figure 17: RTC supply from capacitor
Non-chargeable
Backup Battery
Figure 18: RTC supply from non-chargeable battery
Rechargeable
Backup Battery
Figure 19: RTC supply from rechargeable battery
Module
VRTC
2.2K
RTC
Core
Module
VRTC
2.2K
RTC
Core
Module
VRTC
2.2K
RTC
Core
27
Smart Machine Smart Decision
2016-07-07