SIM900D Hardware Design
C
h
arge-onl
y Mode
Connect charger to module’s VCHG Pin
while SIM900D is in POWER DOWN
mode.
IMPORTANT: Here Charge-only mode is
charging when power down it means that
not all software tasks are running.
z
Battery can be charged when GSM
engine is not registered to GSM
network;
z
Only a few AT commands is available
as listed below.
Note: VBAT can not provide much more than 5mA current while SIM900D module is during the DDLO
charge state. In other words it is strongly recommended that VBAT should not be the main power supply in the
application subsystem while SIM900D module is during the DDLO charge state.
Table9: AT Command usually used in
Charge-only
mode
AT command
Function
AT+CCLK
Set data and time of RTC
AT+CPOWD
Power down
AT+CBC
Indicated charge state and voltage
AT+CFUN
Start or close the protocol
Set AT command
“
AT+CFUN =1
”,module
can be transferred from Charge-only mode to
Charging in normal mode, In Charge-only
mode, the default value is 0
3.5.5 Charger requirements
Following is the requirements of charger for SIM900D.
- Simple transformer power plug
- Output voltage: 5.0V-6V
- Minimum supply current : 750mA
- A 10V peak voltage is allowed for maximum 1ms when charging current is switched off.
-
A 1.6A peak current is allowed for maximum 1ms when charging current is switched on
3.6 Power Saving
There are two methods for the module to enter into low current consumption status. “AT+CFUN” is used to set
module into minimum functionality mode and DTR hardware interface signal can be used to lead system to be in
SLEEP mode (or slow clocking mode).
SIM900D_HD_V1.02
09.04.2010
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