Siemens S55 Repair Documentation page 36

Timing of the Battery Voltage Measurement
Unless the battery is charging, the measurement is made in the TX time slot. During
charging it will be done after the TX time slot. At the same time, either the battery
temperature (in the I-branch) and the battery voltage (in the Q-branch) or the ambient
temperature in the I-branch can be measured (the possibility of measurement in the
Q-branch, the analogue evaluation of the battery coding, is used for HW-Coding).
Other combinations are not possible. For the time of the measurement the multiplexer
in the EGAIM must be programmed to the corresponding measurement.
Recognition of the Battery Type
The battery code is a resistor with a resistance depending on the manufacturer.
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.
USB Charging
For battery voltages above 3.2 Volt and normal 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) with a supply voltage between 3.6 and
5.4 Volt is detected by the POWER SUPPLY ASIC during active mode of the phone.
To enable this charging mode, the mobile phone must be registered (logged on) to a
USB Host. The Charge-Only and Trickle-Charge Mode is not supported because of
USB Spec. restrictions. The charge current is controlled by the POWER SUPPLY
ASIC.
INFO:
* C-rate
The charge and discharge current of a battery is measured in C-rate. Most portable
batteries, are discharge with 1C. A discharge of 1C draws a current equal to the
battery capacity. For example, a battery value of 1000mAh provides 1000mA for one
hour if discharged at 1C. The same battery discharged at 0.5C provides 500mAfor two
hours. At 2C, the same battery delivers 2000mA for 30 minutes. 1C is often referred to
as a one-hour discharge; a 0.5 would be a two-hour, and a 0.1C a 10 hour discharge.
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