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Power Supply & Integrated Charging - Siemens S45 Service Manual

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Power Supply and Integrated Charging
Overview of HW Structure
All the important functions for the power supply of the phone are carried out by the supply
ASIC.
The POWER-pin of the I/O-Connector is for charging the battery with an external power
supply. For accessories which provide a variable charge current, the current will be set via a
further pin SB (current byte) (e.g. S25 chargers corresponding to CarKits etc.).
The standard K45 power supply is unregulated and therefore does not react to the SB
signal, but the SB signal will still be used to distinguish the various power connections.
The following restrictions must be observed:
• The phone cannot be operated without battery inserted.
• The phone will be damaged if the battery is inserted with wrong polarity (the mechanics
of the phone prevent the battery from being put in the wrong way round. The electrics
system assumes that the battery has been inserted correctly. This must be ensured via
suitable QA measures).
Inside the LiIon-battery-pack is a protection-circuit, consisting of a small elecronic circuit and
a polyfuse, to prevent the battery from overcharging, deep discharge and overcurrent
Battery
As a standard battery an Li-Ion battery with a nominal capacity of 840mAh@1 CA, 830mAh
@GSM 2.0/0.2A will be used.
Charging Concept
The battery is charged in the unit itself. The hardware and software is designed for Li-Ion
with 4.2V technology.
Charging is started as soon as the phone is connected to an external charger. If the
phone is not switched on, then charging shall take place in the background (the
customer can see this via the "Charge" symbol in the display). During normal use the
phone is being charged (restrictions: see below).
Charging is enabled via an MOS switch in the phone. This MOS switch closes the circuit
for the external charger to the battery. The processor takes over the control of this switch
depending on the charge level of the battery, whereby a disable function in the STV-
ASIC hardware can override/interrupt the charging in the case of overvoltage of the
battery (only for NEC Batteries).
A third line (SB) shall be used for recognition and control of the S2x charger The SB will
be set at a constant 141, which corresponds to a current of 600mA. To distinguish the
charging units the C25 charger (150mA charging current) will have a short circuit to the
ground, whereas the rapid charger, S25 (1A maximum charging current) will have a high
impedance input. The K45 NAG and the P35 NAG will also be fitted with a high
impedance input and will therefore be recognised as a rapid charger. The charging
software is able to charge the battery with an input current within the range of
350-600mA. If the Charge-Fet is switched off, then no charging current will flow into the
battery (exception is trickle charging, see below).

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