SIM340 Hardware Design
module switch off
automatically
3.7 RTC backup
The RTC (Real Time Clock) power supply of module can be provided by an external capacitor or
a battery (rechargeable or non-chargeable) through the VRTC on the board-to-board connector.
There is a 10K resistance has been integrated in SIM340 module used for limiting current. You
need only a coin-cell battery or a super-cap to VRTC to backup power supply for RTC.
Note: The VRTC couldn’t be designed to a NC pin in your circuit. You should connect the
VRTC pin to a battery or a capacitor.
The following figures show various sample circuits for RTC backup.
RTC
Core
10K
MODULE
VRTC
Non-chargeable
Backup Battery
Figure 12: RTC supply from non-chargeable battery
RTC
Core
10K
MODULE
VRTC
Rechargeable
Backup Battery
Figure 13: RTC supply from rechargeable battery
SIM340_HD_V3.09
18.03.2009
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