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SIM548C Hardware Design
Charging
in
normal
AT+CPOWD
→
“Ghost
mode”, then
disconnect
charger
Disconnect
the charger
Switch off module
by AT+CPOWD
or using
PWRKEY
No direct
transition
Alarm
mode
Use
PWRKEY pin
or wait
module
switch off
automatically
Use
AT+CFUN
No transition
Use AT+CFUN
let module enter
Normal mode,
then connect the
charger to VCHG
pin of module
3.8 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 PIN 11 on the board-to-board connector. There
is a 10K resistance has been integrated in the GSM part of the module used for limiting current.
You need only a coin-cell battery or a super-cap to PIN 11 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.
Figure
11
: RTC supply from non-chargeable battery
SIM548C_HD_V1.01
09.05.2008
41
Содержание SIM548C HD V1.01
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