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SIM5218E Hardware Design
3.6 RTC backup
The RTC (Real Time Clock) power supply of module can be provided by an external battery or a
battery (rechargeable or non-chargeable) through the VRTC (PIN11) on the board-to-board
connector. You need only a coin-cell battery or a super-cap to VRTC to backup power supply for
RTC. The discharge current is smaller than 10uA.the module could update local time based on
universal time and time zone from network.(This feature must be supported by network ).If using
this feature, please refer AT command AT+CTZU and AT +CTZR.
Note: The VRTC default state can be designed to a NC pin in your circuit. If you need to use
the VRTC, You may connect the VRTC pin to a battery or a capacitor.
The following figures show various sample circuits for RTC backup. The series resistor is
programmable from 800 Ohm to 2100 Ohm
Figure 8: RTC supply from non-chargeable battery
Figure 9: RTC supply from rechargeable battery
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SIM5218E_HD_V1.03
11.06.2009
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