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Circuit Description
4-4 Hands-Free Kit
Hands-free board is largely composed of car
adapter circuit and Hands-free circuit.
4-4-1 Car Adapter Circuit
POWER SUPPLY
Input power switching circuit : This circuit
includes Short protection circuit, and Power
switching control circuit. It supplies power for
HHP and hands-free kit.
+13.5V switching circuit (Q801, 802) : This circuit
switches power for power amplifier using MPU
mute signal.
HHP power circuit : This circuit is Switching
regulator. Input voltage is +13.6v, output voltage
is +5.8v.
Vcc regulator (U704) : This circuit regulates Vcc
(+5V).
CHARGER CIRCUIT
This circuit charges battery pack by detecting the
temperature of battery, the slope of temperature,
the slope of the voltage of battery, and charging
time, etc.
During charging, the charger LED turn on red.
When charging is completed, the charger LED
turns on green.
Battery Type Capacity
S t a n d a r d
8 5 0 m A H
E x t e n d e d
1 5 0 0 m A H
4-6
Charge Current Charge Voltage
3 0 0 m A
6 . 2 V
6 0 0 m A
6 . 7 V
Voltage detection circuit : Charging circuit is
designed to stop charging when the voltage of
battery is dropped.
The voltage of battery is entered to A/D converter
located in U703 #2.
Temperature detection circuit : The temperature
of battery is measured by missing NTC thermistor.
NTC themistor has a characteristics of Log-scale. It
obtains a linear characteristics by the parallel
connection of resistors.
4-4-2 Hands-free Circuit
POWER SUPPLY (U704,U808)
+5V is regulated by U704 for hands-free circuit,
and -5V is regulated by U808.
TX PATH
The audio signal from external mic(JP705) flows
into U802 pin #11. U802 includes Amplifier and
Control circuit for hands-free operatin. U801A
amplifies input signal. Output signal is
transmitted to HHP.
RX PATH
Input audio signal cancels noise by difference
amplifier (U801c). U802 performs hands-free
action. The RX audio signal is input (U805). The
speaker drive amp (U804) amplifies the Rx audio
signal and the output of U804 goes out of speaker.
Samsung Electronics
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