Samsung sf150t Service Manual page 38

1) TX CIRCUIT
The output signal coming from internal modem
KS16118 enters MX93000AFC through AUX2
terminal after amplfied by OP AMP U1.
That signal passes through internal switch, is
amplified by LIN-DRV amplfier and is sent to LIU
board through LOUT terminal.
5-5 TAD
TAD circuit consists of a voice coprocessor to record and play voice messages and voice memory.
5-5-1 DSP
This circuit consists of host interface, memory
interface, CODEC interface.
receives data to the compressed voice data to and
from KS16118.
Memory interface sends and receives data to the
compressed voice data to and from DRAM to play
back and record voice data.
DSP communicates with host KS16118 through host
interface.
5-5-2 Recording Path
The voltage is supplied with MIC as using the
MX93000AFC's Vref Voltage (2.25V), and the voltage
entering into MIC is trasmitted to electric signal and
enters into MX93000AFC's MIC terminal.
Input signal is amplified by MX93000AFC's ALC
until maximum 26dB (Max. 3V
signal size.
The signal enters into PCM CODEC that converts to
D/A and compresses in the DSP Chip and stores in
DRAM.
SF150T
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2) RX CIRCUIT
The signal goming into LIU terminal through LIU
board is amplified by MX93000AFC's PRE-PGA,
passes through internal switch and goes into FILT
terminal.
After the singal is diminished by OP AMP U1, it
enters internal modem of KS16118.
5-5-3 Play Path
The signal stored in DRAM is decomressed in DSP
and enters into MX93000AFC.
Input signal is converted to D/A again and is
amplified by LIU-DRV amplifier and comes into
LOUT terminal through or comes into terminal
after being attanuated by ATT (Electronic Volume)
or SPK-DRV.
5-5-4 Voice Backup
+5V is supplied for DSP or voice memory through
VBT when power is on.
When power is off, +5V is supplied from the 9V
backup battery.
When supply voltage is "ON", U9(5V Voltage
Regulator) makes 5V Supply Voltage.
The signal is supplied with DSP or DRAM and it
caused that the data is protected.
When supply voltage is "OFF", U9 makes 5V Voltage
as using the 9V Battery.
And then the voltage is used to "backup supply
voltage" in DSP or DRAM.
If the supply voltage were "OFF" as using the full
charged 9V Battery, voice data is usually protected
for twenty hours.
Circuit Description
5-7