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LEON-G100/G200 - System Integration Manual

GSM.G1-HW-09002-C Preliminary System description

Page 22 of 75

Figure 9: Connection of an external DC supply used as charger and a Li-Ion battery to the LEON-G200 module

When charger detection is implemented: a valid charger is recognized if the voltage provided to V_CHARGE and

CHARGE_SENSE pins is 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.

To prevent damage to the module and the battery, use only chargers that comply with the

characteristics given in section 1.5.3.1.

The algorithm that controls battery charging, implements a classic Li-Ion battery charging process, divided into 4

phases:

1. Pre-Charge, at slow current for deeply discharged batteries

2. Fast Charge, at the maximum current provided by the external DC supply used as charger (must be current

limited)

3. Top Charge, to complete the over-charging of the batteries, after the maximum voltage (4.2 V for Li-Ion

battery) is reached

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) and the device is in not-powered

mode, the charger circuit starts pre-charging when a valid voltage is provided to the 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 100 Hz and a duty cycle of 12.5%. This means the average charge current is reduced to

avoid overheating of charger parts and to gently charge the deeply discharged batteries. Pre-charging is

hardware controlled and continues as long as the VCC voltage reaches the 3.1 V typical limit, so the module is

able to start the following charging phase.

During fast charging (following the pre-charging phase) the charge transistor switch mounted inside the module

can be driven by software according to the charge algorithm. The duty cycle of the charge current never reaches

100%: the charge switch is not closed for 100% of the time but still pulsed with a 100 Hz clock with an on-time

CHARGE_SENSE

V_CHARGE

LEON-G200

Charger

voltage and current limited

VCC

GND

Li-Ion Battery

500 mAh … 1100 mAh

CHARGE_SENSE

V_CHARGE

LEON-G200

Charger

voltage and current limited

VCC

GND

Li-Ion Battery

500 mAh … 1100 mAh

Figure 8: Connection of an external DC supply used as charger and a Li-Ion battery to the LEON-G200 module

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