Samsung SCH-211 Service Manual page 29

Circuit Description
CURRENT DETECTION CIRCUIT : R5, R6,
R11, R12, HIC
Battery charging current is changed voltage
through R5, R6, R11, R12. This voltage inputed
u-COM to 16 times amplifiered through HIC.
VOLTAGE DETECTION CIRCUIT : HIC
u-COM A/D through HIC pin 12, 13 detected
voltage.
5-5 Hands-Free Kit
5-5-1 Charging Circuit
A constant voltage is used for the hands-free kit.
This circuit converts DC 12V input current to 8.4V
DC to charge the battery. When the battery is fully
charged, the charge current drops and the circuit
operates as a constant voltage.
5-5-2 u-Processor
Micro processor controls charging power and
charging current to protect the phone. It also
allows to communicate with a HHP, and to con-
vert from hands-free mode to private mode, and
vice verse. It adjusts speaker volume at 8 steps
and attenuates echo and noise occurred during
conversation.
5-8
BATTERY TEMPERATURE DETECTION CIR-
CUIT : HIC, TH1
Battery temperature detection determined
temperature by ues of thermistor registor
variation of THI by HIC.
CURRENT LIMIT CIRCUIT : HIC
When soft-change, current detection circuit
limited current flow to battery, reference voltage
more than detected current, detected current and
HIC internal reference voltage.
5-5-3 Speaker circuit
This circuit eliminates HHP noise, and controls
the sound quality and speaker volume using ana-
log C-mos IC which checks the speaker signal up
to 8 steps. 5W audio amplifier amplifies the speak-
er signal.
5-5-4 Microphone Circuit
This circuit separates ground to eliminate the
noise occurring from the HHP antenna and micro-
phone. u-processor controls this circuit to attenu-
ate echo which may occur in Land side.
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