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1. Description of Circuitry
Description of Power Supply Circuit Operations
(1) Introduction
The power supply circuits are mainly formed by the follow-
ing blocks.
· Power supply switching: FET Q5010 and control IC IC501
· 12V(HDD) power supply output
· 5V power supply output: IC531
· 3.3V power supply output: IC551
· 2.5V power supply output: IC581
· 12V (AD) power supply output: IC582
(2) Switching power supply control IC
IC501 (FA3641) is an 8-pin PWM switching control IC that
can directly drive the power MOSFET.
The oscillation frequency is decided by pin 1, secondary
side feedback is provided by pin 2, controlling output of
the secondary side. Overcurrent detection is done by pin 3
(overcurrent protection operation), and an overvoltage
protection function is established at the pin 6 VCC lead.
When these overcurrent and overvoltage movements
begin to work, they generate latch-up movement as
circuits.
(3) 12V(HDD) Power Supply Output
12V output (for the hard disk). Feedback from this 12V
goes to IC501, enabling PWM control.
(4) 5V Power Supply Output
5V output. The 5V is produced by IC531 (MD1222N), a
32-pin surface mount SSOP DC/DC converter (chopper
control).
The DC/DC converter can set output voltage by discretion,
according to external resistance.
Input leads are pins 18~21, output leads are 11~14.
(5) 3.3V Power Supply Output
3.3V output. The 3.3V is produced by IC551 (MD1222N),
a 32-pin surface mount SSOP DC/DC converter (chopper
control).
The DC/DC converter can set output voltage by discretion,
according to external resistance.
Input leads are pins 18~21, output leads are 11~14.
(6) 2.5V Power Supply Output
2.5V output. IC581 (SI-3025LSA) is an 8-pin surface
mount IC.
Input leads are pins 1 and 3, output leads are 7 and 8.
(7) 12V Power Supply Output
12V output (for the audio circuits). 12V is produced by the
TO-220 package regulator of the 5-pin IC582 (SI-3090F).
Input leads are pins 2 and 5, output lead is pin 3.
Explanation of Hard Disk Circuit Operations
(1) Introduction
(1-1) DM-A
(a) Input/Output Video Filter: Q2011, 12, 13, 14, 21, 22, 23,
25, 31, 32, 33, 34, 41, 42, 43, 44, 45, 46, 48, 61, 62, 63,
65, IC202, 203, 204
Cuts frequencies above a sample frequency of the input sig-
nal and eliminates entry of return noise.
Amplifies to match the decoder input levels.
Eliminates noise that is included in the encoder video sig-
nal, and mixes brilliance and color signals then outputs them.
(Composite Out)
Brilliance and color signals are output separately. (S-Out)
(b) DECODER video IC215
Converts the received video signal to digital, separates the
brilliance and color signals and makes them both 8 bit sig-
nals.
(c) Audio Input/Output audio IC206, 207, 208
Adds AGC to the Line input signal and passes it to the buffer
for input to the audio A/D converter of the ASIC.
Sound output from the ASIC D/A out is passed through a
filter and output through playback AGC.
When a microphone is connected, the sound output goes
through the microphone amplifier and input is automatically
connected to the microphone side.
(d) Serializer IC212
Serializes parallel digital data. Uses differential method.
(e) Deserializer IC211
Converts serial differential data to parallel.
(1-2) DM-B
(a) ASIC Operations IC251
Audio A/D, D/A.
Single channel audio signal digital conversion/analog con-
version.
8 bit sample frequency 8kHz
MJPEG Coder
Functionality for compression/expansion of motion JPEG im-
ages and for simultaneous compression/expansion.
Video Encoder
Forms chroma signal according to digital chrominance sig-
nals. (NTSC/PAL)
Video D/A
Converts digital brilliance signal and outputs it as analog.
Converts digital chroma signal and outputs it as analog.
Digital I/F
Interface circuit for digital data of MPX and HDR.
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