Philips DVDR3305/02, Руководство по обслуживанию, Страница: 47 / 73

EN 47 3139 785 3093x 8. Circuit- and IC description
8.1. Front Board (Panel – D Key)
8.1.1. General
This board consists of the following parts:
•
Slave μ P
•
Frontend (Audio & Video)
•
VFD Heater voltage Generator
8.1.2. Slave μ P (IC 7105: UPD16316GB)
The core element of the Front D Keyboard is the slave
μ P. It runs on a 5V supply and is responsible for the following
functions:
•
Interface with the Domino chip on the Digital Board
•
Evaluation of the keyboard matrix within Front board
•
Decoding the remote control commands from the infra-red
receiver
•
Activation and control of the display
•
Timer Wake-up activation
It runs on two clock frequencies namely:
•
5MHz for normal operation
•
32.768KHz for the real time clock
8.1.3. Interface to the Domino chip
It communicates with the Domino Host on the Digital board
via a 6-wire synchronous serial interface. The Host is always
the master to generate the communication clock to the slave
μ P irrespective of the direction of data transfer.
8.1.4. Evaluation of the keyboard matrix
A key matrix is used on the Front board. The slave μ P does
the key scanning with FIP9 - FIP24 (pin 23-26 and 29-40) as
output and KEY_A - KEY_C (pin 41-43) as input. Each key is
assigned a key code based on the output and input ports, and
the slave
μ P will do the evaluation by getting the key codes.
8.1.5. IR receiver and signal evaluation
The IR receiver on the Front Board contains a selectively
controlled ampli
fi er as well as a photodiode. The photo-diode
changes the received infrared transmission to electrical
pulses, which are then ampli
fi ed and demodulated. On the
output of the IR receiver, a pulse sequence with TTL-level,
which corresponds to the envelope curve of the received
IR remote control command, can be measured. This pulse
sequence is fed into the slave
μ P for further processing via
pin 13.
8.1.6. Vacuum Fluorescent Display [1203: HUV-08SS65T]
The VFD is fully controlled and driven by the slave μ P.
8.1.7. VFD Heater Voltage Generator
The oscillator circuit provided by [5100, 2101, 2102 & 7100]
provides the necessary sine wave signal for transistors [7101,
7102 & 7103] to generate the 50% duty-cycle 48KHz AC
square-wave signal for the
fi lament of the VFD.
8.1.8. Timer Wake-up activation
During the Standby mode, the slave μ P provides a wakeup
call (POWER_CTL-line switches to high) to the Domino Host
on the Digital Board. It will then starts up and asks for the
wake-up reason.
8. Circuit- and IC description
8.2. Analog Board
8.2.1. General
The pc board consist of the following parts:
•
Fan Control (OPTION)
•
Power Supply Unit
•
Tuner Frontend
•
Audio ADC/DAC
8.2.2. Fan Control
The Laser on the OPU of the drive is very sensitive to
temperature. A fan control circuit [7802 & 7803] is built into
the board as a provision. The fan is ON when the set is in
active mode, and OFF when the tray opens. When the set is
in Standby mode, the fan is switched off. The control of the
fan is coming from the Digital Board.
8.2.3. Power Supply Unit
This power supply functions on a circuitry combination
of a SMPS control IC [7400], switching FET [7401] and
transformer [5400] as a switched-mode power supply
(SMPS).
Feedback control is provided by the IC 7404, which compares
the 5V-output voltage via voltage dividers [3421, 3422 &
3423] with an internal 2.5V reference voltage. The output
voltage is fed to an optocoupler [7403] that provide the
insulation between the primary and secondary parts as a
current value into pin 3 of the IC 7400.
The following are the various supply lines provided:
•
3V3SW to CU, DAC_ADC, Digital Board
•
5V to IOA, IOV, CU, CINCH, MSP, DIGIO and
FV
•
5N to MSP (provision only) and Digital Board
(provision only)
•
5VE to Basic Engine
•
5V_BE to Digital Board
•
5NSTBY to IOA, CINCH and DAC_ADC
•
5VSTBY to IOA, IOV, FV, MSP, DAC_ADC, Front
Board
•
8VSTBY to MSP
•
12V to Digital Board
•
12VSTBY to CU, IOV, DAC_ADC, Front Board
•
12VE to Basic Engine and Digital Board (provision
only)
•
33VSTBY to FV
•
VGNSTBY to Front Board
Standby modes:
In Standby mode, the STBY control line is low, switching off
the 3V3SW, 5V, 5N (provision), 5VE, 12V and 12VE supply
and thus reducing the power consumption.