Q2406 Datasheet, PDF (38/81 Pages) List of Unclassifed Manufacturers – SELF CONTAINED E GSM/GPRS 900/1800 OR 850/1900 BI BAND MODULE

WM_PRJ_Q2400_PTS_002 - 002
24th January 2003
2.13.1 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 150mΩ is required.
(*) : To be parametrized as per battery manufacturer
2.13.2 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.
Calculation examples
CTN(25°C) = 47K
CTN(55°C) = 10K
CTN(-10°C) = 300K
CTN(-10°C) x VCC = ( CTN(-10°C) + R1 ) x BAT-TEMP (full range)
R1= 47K " BAT-TEMP(-20°C) = 2.42V
BAT-TEMP(55°C) = 0.49V
R(-20°C) = R1//CTN(-10°C) = 40K
R(+55°C) = 8K
With C= 10nF ::
RC(-20°C) = 400µs
RC(+55°C) = 80µs
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