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SIM548C Hardware Design
Figure
10
: Battery charger and pack
The TEMP_BAT function should be supported by the software in the module. It’s a customization
function. The R
TEMP
is a NTC thermistor. We recommend to use NCP15XH103F03RC from
MURATA. The impedance of the NTC thermistor is 10Kohm in 25
℃
. Please refer to the above
figure for the reference circuit.
3.5.1 Battery pack characteristics
The GSM part of the module has optimized the charging algorithm for the Li-Ion battery that
meets the characteristics listed below. To use the GSM part of the module’s charging algorithm
properly, it is recommended that the battery pack you integrated into your application is compliant
with these specifications. The battery pack compliant with these specifications is also important
for the AT command “AT+CBC” to monitor the voltage of battery, or the “AT+CBC” may return
incorrect battery capacity values.
z
The maximum charging voltage of the Li-Ion battery pack is 4.2V and the capacity is
recommended to 580mAh. The capacity of battery packs down to 580mAh or more than
580mAh are allowed, too.
z
The battery pack should have a protection circuit to avoid overcharging,overdischarging and
over-current. This circuit should be insensitive to pulsed current.
z
On the GSM part of the module, the build-in power management chipset monitors the supply
voltage constantly. Once the Under-voltage is detected, the GSM part of the module will
power down automatically. Under-voltage thresholds are specific to the battery pack.
z
The internal resistance of the battery and the protection circuit should be as low as possible.
SIM548C_HD_V1.01
09.05.2008
33
Содержание SIM548C HD V1.01
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