LEON-G100 / LEON-G200 - System Integration Manual
GSM.G1-HW-09002-G3
Preliminary
System description
Page 29 of 125
Maximum voltage
The voltage limit of the external charger must be
≤
15 V. Since the module is not provided with an internal
overvoltage protection circuit on
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, so the external supply used
as charging source must be voltage limited with a voltage limit
≤
15 V.
Minimum voltage
The charger must be able to provide a minimum open circuit output voltage
≥
5.6 V for the valid charger
detection.
Maximum current
The current limit of the external charger must be
≤
1.0 A (that is the module absolute maximum rating as
charging current) and must be lower than the maximum DC charging current specified by the used battery.
Since the module is not provided with an internal over-current protection circuit on
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, so the external supply used as charging source must be current limited with a proper
current limit.
Minimum current
A minimum acceptable value for the charging current is not specified, but the charging current value should be
large enough to perform the whole battery charging process within the time interval defined by the application
and the charging current value should be greater than the highest possible average current consumption of the
system that is supplied by the battery (i.e. the module plus any additional device on the application board) to let
the increase of the battery level while the system reaches its highest current consumption. For example, if the
battery supplies only the module and the charging current value is equal to 400 mA, the battery level can be
increased also when the module reaches its highest current consumption (during a GPRS connection). If some
other devices are supplied by the battery beside the module, when the battery is deeply discharged (VCC below
3.1 V typical), the module is switched off and the pre-charging current (~1/8 of the external charger current
limit) is enabled: this current should be greater than the highest possible average current consumption of the
system to let the increase of the battery level while the system reaches its highest current consumption.
For example, Figure 15 shows the valid area for the charger V-I output characteristics using a battery with a
maximum DC charging current equal to 600 mA: the maximum acceptable charging current is defined by the
battery requirement (600 mA).
