LEON-G100 / LEON-G200 - System Integration Manual
GSM.G1-HW-09002-G3
Preliminary
System description
Page 27 of 125
The
V_CHARGE
pin is the charger supply input: it sinks the charge current that is typically in the order of several
hundred of mA. The
CHARGE_SENSE
pin is connected to an internal ADC converter to measure the charging
voltage: it senses the charger voltage and sinks a few µA.
V_CHARGE
and
CHARGE_SENSE
pins must be externally connected together as shown in Figure 14.
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
V_CHARGE
and
CHARGE_SENSE
pins
of the module.
If the battery charging process is not managed by the GSM module,
V_CHARGE
and
CHARGE_SENSE
pins can be left floating on the application board.
LEON-G200
+
Charger
Voltage and
current limited
Li-Ion
Battery
5
CHARGE_SENSE
4
V_CHARGE
GND
50
VCC
GND
-
+
-
Figure 14: Connection of an external DC supply used as charger and a Li-Ion battery to the LEON-G200 module
To prevent damage to the module and the battery, use only chargers that comply with the
characteristics given in section 1.5.4.2.
1.5.4.1
Charging process description
A valid charger is recognized if the voltage provided to
V_CHARGE
and
CHARGE_SENSE
pins are within the
operating range limits (5.6 V minimum, 15 V maximum). If the module is switched off, the charger circuitry
generates the power on in charging mode after charger detection.
The algorithm that controls battery charging, implements a classic Li-Ion battery charging process, divided into 4
phases:
1.
Pre-Charge, at low current, for deeply discharged batteries (
VCC
voltage within 0 V and 3.1 V typical)
2.
Fast Charge, at the maximum current provided by the external DC supply used as charger that must be
current limited, for discharged batteries (
VCC
voltage within 3.1 V typical and 4.2 V typical)
3.
Top Charge, to complete the over-charging of the batteries, after the maximum voltage is reached (
VCC
voltage equal to 4.2 V typical)
4.
Trickle Charge, to maintain the battery at higher level of charge, if the external DC supply used as charger
remains connected
If the batteries are deeply discharged (
VCC
voltage within 0 V and 3.1 V typical with 7% tolerance due to
change in temperature and life time), and the device is in not-powered mode, the charger circuit starts
pre-charging when a valid voltage is provided to
V_CHARGE
and
CHARGE_SENSE
pins of the module. In the
pre-charging phase, the charge transistor switch mounted inside the module is pulsed with a 100 Hz clock and
an on-time of 12.5% of a period. This means the average charge current is reduced to avoid overheating of
