GE863 datasheet(13/69 Pages) ETC1

13 / 69 page

Telit GE863-QUAD / GE863-PY

Hardware User guide

1vv0300697, Rev. ISSUE#0, - 21/11/05

page 13 of 69

3.2.1.3 Battery Source Power Supply Design Guidelines

• The desired nominal output for the power supply is 3.8V and the maximum voltage allowed

is 4.2V, hence a single 3.7V Li-Ion cell battery type is suited for supplying the power to the

Telit GE863-QUAD module.

The three cells Ni/Cd or Ni/MH 3,6 V Nom. battery types or 4V PB types MUST NOT BE

USED DIRECTLY since their maximum voltage can rise over the absolute maximum

voltage for the GE863-QUAD and damage it.

NOTE: DON'T USE any Ni-Cd, Ni-MH, and Pb battery types directly connected with GE863-QUAD.

Their use can lead to overvoltage on the GE863-QUAD and damage it. USE ONLY Li-Ion battery

types.

• A Bypass low ESR capacitor of adequate capacity must be provided in order to cut the

current absorption peaks, a 100μF tantalum capacitor is usually suited.

• Make sure the low ESR capacitor (usually a tantalum one) is rated at least 10V.

• A protection diode should be inserted close to the power input, in order to save the GE863-

QUAD from power polarity inversion. Otherwise the battery connector should be done in a

way to avoid polarity inversions when connecting the battery.

• The battery capacity must be at least 500mAh in order to withstand the current peaks of 2A;

the suggested capacity is from 500mAh to 1000mAh.

3.2.1.4 Battery Charge control Circuitry Design Guidelines

The charging process for Li-Ion Batteries can be divided into 4 phases:

• Qualification and trickle charging

• Fast charge 1 - constant current

• Final charge - constant voltage or pulsed charging

• Maintenance charge

The qualification process consists in a battery voltage measure, indicating roughly its charge

status. If the battery is deeply discharged, that means its voltage is lower than the trickle

charging threshold, then the charge must start slowly possibly with a current limited pre-

charging process where the current is kept very low with respect to the fast charge value: the

trickle charging.

During the trickle charging the voltage across the battery terminals rises; when it reaches the fast

charge threshold level the charging process goes into fast charge phase.

During the fast charge phase the process proceeds with a current limited charging; this current

limit depends on the required time for the complete charge and from the battery pack capacity.

During this phase the voltage across the battery terminals still raises but at a lower rate.

Once the battery voltage reaches its maximum voltage then the process goes into its third state:

Final charging. The voltage measure to change the process status into final charge is very

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