Specifications

LEON-G100/G200 - System Integration Manual
GSM.G1-HW-09002-C Preliminary System description
Page 23 of 75
of >99% of a period. The remaining off time is used to check if the AC-DC wall adapter is still connected since
detection is critical when charging switch is closed.
The integrated charging circuit doesn’t have any voltage or current limitation, therefore the charger must be
chosen very carefully: during the fast charging phase, the battery is charged with the maximum DC current
provided by the external DC supply used as charger, which must be current limited as described in the charger
specification section.
When the battery voltage reaches the nominal maximum voltage (4.2 V for Li-Ion battery), charging enters the
constant voltage phase (top charge algorithm): in this phase the average charging current decreases until the
battery is completely charged.
After the constant voltage phase, the battery is maintained at a higher level of charge with the trickle charge
algorithm until an external charger is connected to the module.
The charging process is enabled only within the temperature range: from 0°C to 50°C with a 5°C hysteresis to
prevent rapid switching on and off as the temperature drifts around the set point: it is disabled when the
temperature falls below 0°C and then enabled when it rises above 5°C; it is disabled when the temperature rises
above 50°C and then enabled when falls below 45°C.
Battery over-voltage detection is implemented to switch-off charging if e.g. the battery is removed during
charging. The over-voltage threshold level is set to the nominal value of 4.47 V (evaluated with 2% of tolerance).
1.5.3.1 Charger specification
To avoid damage to the module, the external supply used as charging source must be voltage and current
limited.
The value of the charger voltage limit must be lower or equal to 15 V. Since the module is not provided with an
internal overvoltage protection circuit on the V_CHARGE and CHARGE_SENSE pins, the charging voltage must
be lower or equal to the maximum acceptable charging voltage value of 15 V at any time: voltage spikes that
may occur during connection or disconnection of the charger must be limited within this value.
The value of the charger current limit must be lower or equal to the value of the battery capacity plus 100 mA:
the maximum acceptable value for the charger current limit depends on the capacity of the Li-Ion battery used.
For example using a 500 mAh battery, the charger current limit must be lower or equal to 600 mA. Since the
module is not provided with an internal over-current protection circuit on the V_CHARGE and CHARGE_SENSE
pins, the charging current must be lower or equal to the maximum acceptable charging current value at any
time: current spikes that may occur during charger connection or disconnection must be limited within this
value.
There may not be any capacitor on the charge path: a straight connection must be provided between the
output of the external supply used as charging source and the V_CHARGE and CHARGE_SENSE pins of
the module.
The charger must be able to provide a minimum open circuit output voltage greater or equal to 5.6 V for the
valid charger detection.
A minimum current for the charger is not specified: this value has to be large enough to perform the whole
battery charging process within the time interval specified by the application. For example using a 500 mAh
battery, the minimum current available by the charger can be 400 mA to reach the complete charge of the
battery within a useful period.
DC supplies with fold-back current protection cannot be used as charger for the module.
Use a charger with the following electrical characteristics:
6 V DC voltage
Current limit equal to the capacity of the used battery (i.e. 500 mA current limit if a 500 mAh battery is
used)
The V-I output characteristics of the external supply used as charger must be within the valid area delineated by:
the maximum acceptable charging voltage (equal to 15 V in any case)
the minimum voltage valid for charger detection (equal to 5.6 V in any case)