Specifications

WM_PRJ_Q2400_PTS_001 - 003
6th November 2002
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Safety
Circuitry
CTN
GND
BAT_TEMP
+VBATT
R1
C1
VCC
Internal Battery
Resistor
Figure 9 : Connection examples
2.12.1 Li-ion charging procedure
A constant current source has to be provided through CHG_IN input in order to
charge the Li-ion battery, and BAT_TEMP input has to be connected to a
battery temperature sensor. During this procedure the voltage of the battery is
accurately monitored.
The Li-ion charging involves two phases. During the first phase, the battery is
charged with a constant current until its voltage reaches 4.1V*. During the
second phase the constant current is pulsed by the module. The width and the
frequency of the pulse change during this phase in order to ensure a safety
charge. The battery is considered as fully charged when, after a pulse, the
voltage remains at a 4.1V* during more than 10s.
The Li-ion battery must have an included safety circuit to avoid any discharge
or overcharge. This circuit is delivered by the manufacturer inside the battery
pack. The impedance of this safety circuit has to be the lowest possible in
order to reduce the drop-out of the voltage. This drop-out is due to the RF
Power Amplifier current (up to 2.0A). A maximum of 150m
Ω
is required.
(*): To be parameterized as per battery manufacturer
2.12.2 How to define R1 and C1
How to choose R1
R1 has to be chosen to have a full range of BAT-TEMP (from 0V to 2.8V) when
the CTN value changes from the minimum to the maximum temperature
How to choose C1
C1 has to be chosen to have a RC filter with a time constant lower than 2ms.