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TD_Repair_L2.5_A70_A75_R1.0.pdf Release 1.0

Measurement of Battery, Battery Type and Ambient Temperature

For the conversion of signals like battery voltage, battery type, temperature, EGOLDlite

provides identical measurement interfaces. Measurement circuit is consisting of external

sensing components and integrated analog multiplexers and switches. Through

corresponding switch settings, the measured signal is passed to input of ADC. 12-bit

conversion results are readout by µc and used for charging control.

Charging Characteristic of Lithium-Ion Cells

LiIon batteries are charged with a U/I characteristic, i.e. the charging current is regulated in

relation to the battery voltage until a minimal charging current has been achieved. The

maximum charging current is approx. 600mA, minimum about 100mA. The battery voltage

may not exceed 4.2V ±50mV average. During the charging pulse current the voltage may

reach 4.3V. The temperature range in which charging of the phone may be started ranges

from 5...40°C, and the temperature at which charging takes place is from 0...45°C. Outside

this range no charging takes place, the battery only supplies current.

Trickle Charging

The POWER SUPPLY ASIC is able to charge the battery at voltages below 3.2V without any

support from the charge SW. The current will by measured indirectly via the voltage drop

over a shunt resistor and linearly regulated inside the POWER SUPPLY ASIC. The current

level during trickle charge for voltages <2.8V is in a range of 20-50mA and in a range of 50-

100mA for voltages up to 3.75V. To limit the power dissipation of the dual charge FET the

trickle charging is stopped in case the output voltage of the charger exceeds 10 Volt. The

maximum trickle time is limited to 1 hour. As soon as the battery voltage reaches 3.2 V the

POWER SUPPLY ASIC will switch on the phone automatically and normal charging will be

initiated by software (note the restrictions on this item as stated below).

Normal Charging

For battery voltages above 3.2 Volt and normal ambient temperature between 5 and 40°C the

battery can be charged with a charge current up to 1C*. This charging mode is SW controlled

and starts if an accessory (charger) is detected with a supply voltage above 6.4 Volt by the

POWER SUPPLY ASIC. The level of charge current is limited/controlled by the accessory or

charger.

Siemens A70 Service Repair Documentation

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