Implemented Charging Technique - SimCom SIM548C HD V1.01 Hardware Design

SIM548C Hardware Design
Product name & type
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Normal voltage
Capacity
Charge Voltage
Max Charge Current
Max Discharge Current
Charge Method
Internal resistance
Over-charge protect threshold.(V)
Released Voltage from Over-charge(V)
Over-discharge protect threshold(V)
Released Voltage from Over-discharge(V)

3.5.3 Implemented charging technique

The GSM part of the module includes the function for battery charging. There are three pins in the
connector related with the battery charging function: VCHG, VBAT and TEMP_BAT pins. The
VCHG pin is driven by an external voltage, this pin can be used to detect a external charger
supply and provide most charging current through the GSM part of the module to battery when
charging is in fast charge state. The module VBAT pin give out charging current from the GSM
part of the module to external battery. TEMP_BAT pin is used for measuring the battery
temperature. Just let this pin open if battery temperature measuring is not your concern.
So it is very simple to implement charging technique, you need only connect the charger to the
VCHG pin and connect the battery to the VBAT pin.
When the GSM part of the module detected the charger supply and the battery are both present,
battery charging will happen. If there is no charger supply or no battery present, the charging will
not be enabled.
Normally, there are three main states in whole charging procedure.
DDLO charge and UVLO charge;
Fast charge;
Trickle charge;
SIM548C_HD_V1.01
SCUD Li-Ion, 3.7V, 800mAh
SCUD (FU JIAN) Electronic CO..LTD
3.7V
Minimum 800mAh
4.200~4.23V
1.2C
2C
CC / CV (Constant Current / Constant Voltage)
≤130mΩ
4.28 ± 0.025
4.08 ± 0.05
2.3± 0.1
2.3± 0.1
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09.05.2008