LG GCE-8240B Service Manual

INTRODUCTION

FEATURES

1. General

1) Enhanced IDE interface.

2) Internal 5.25 inch, halfheight CD-R/RW Drive.

3) 8 Mbytes buffer memory.

4) Audio CD like tray loading of a disc without using a caddy.

5) Power loading and power ejecting of a disc. The disc can also be ejected manually.

6) Supports Power saving mode and Sleep mode.

7) Vertical and Horizontal operation.

8) ExacLink Function.

2. Supported disc formats

1) Reads and writes data in each CD-ROM, CD-ROMXA, CD-I FMV, Video CD, and CD-EXTRA

2) Reads data in Photo CD (Single and Multi session).

3) Reads and writes standard CD-DA.

4) Reads and writes CD-R discs conforming to “Orange Book Part 2”.

5) Reads and writes CD-RW discs conforming to “Orange Book Parts 3”.

3. Supported write method

1) Disc at once (DAO), Session at once (SAO), Track at once (TAO), Variable packet, Fixed packet, and Multi-session.

4. Performance

1) Random 110 ms average access time.

2) CD-R Record speed : 8X, 12X, 16X, 16-24X Z CLV.

3) CD-RW Record speed : 2X, 4X, 10X.

4) CD-ROM : Max 6,000 KB/s(Max 40x) Sustained Transfer rate.

5) Supports real time error correction and real time layered error correction at each speed.

6) PIO Mode 4, Multi DMA Mode 2 .

7) Multimedia MPC-3 Spec compliant.

8) Support CD-TEXT read/write.

5. Audio

1) Output 16 bit digital data over ATA interface.

2) 8 Times Digital Filter for CD Audio

3) Software Volume Control

4) Equipped with audio line output and headphone jack for audio CD playback.

5) Front panel Volume Control for Headphone Output.

This service manual provides a variety of service information. It contains the mechanical structure of the CDR/RW Drive and the electronic circuits in schematic form. This CD-R/RW Drive was manufactured and assembled under our strict quality control standards and meets or exceeds industry specifications and standards. This CD-R/RW drive is an internal drive unit designed for use with IBM PC, HP Vectra, or

compatible computer. It can write as much as 700 Mbytes of digital data into CD-R/RW disc, and can read as much as 650 Mbytes of digital data stored in a CD-ROM, CD-R and CD-RW disc. This CD-R/RW Drive can easily meet the upcoming MPC level 3 specification, and its Enhanced Intelligent Device Electronics (E-IDE) and ATAPI interface allows Plug and play integration in the majority of today’s PCs without the need of an additional interface card.

SPECIFICATIONS

1. SYSTEM REQUIREMENTS

-CPU: IBM Compatible Pentium 350MHZ (or faster)

(For 24X Write speed, 500MHz or faster recommended.)

-64MB Memory or greater

2. SUPPORTING OPERATING SYSTEM

3. GENERAL

1) Host Interface.......................................................................................................................ATAPI compliant

2) Read Function

• Acceptable discs ...............................................................CD-ROM Mode1 (basic format), CD-ROM XA

CD-Audio Mixed Mode (Audio and Data Combined) Photo-CD (Single and Multi-Session) CD-I FMV, Video CD CD-Plus/CD-Extra, CD-R (Conforming to “Orange Book Part2”) CD-RW (Conforming to “Orange Book Part3”)

3) Write function

• Applied Format..................................................................CD-ROM Mode-1

CD-ROM XA CD-Audio Mixed Mode (Audio and Data Combined) Video CD, CD-I FMV CD-Plus/CD-Extra

• Writing Method..................................................................Disc at once(DAO)

Session at once(SAO) Track at once(TAO) Variable packet writing Fixed packet writing Multi-session

4) Cache memory (R/W) .........................................................8 Mbyte

5) Disc diameter ......................................................................12 cm /8 cm

6) Data capacity (Yellow-Book)

• User Data/Block ................................................................2,048 bytes/block (Mode 1 & Mode 2 Form 1)

2,336 bytes/block (Mode 2) 2,328 bytes/block (Mode 2 Form 2) 2,352 bytes/block (CD-DA)

7) Rotational Speed

CD-Audio.............................................................................8x~24x(CAV) Approx.3,600 r/min

DAE speed ..........................................................................18x~40x(CAV) Approx.8,400 r/min

CD-RW data ........................................................................14x~32x(CAV) Approx.6,500 r/min

CD-ROM/CD-R data............................................................18x~40x(CAV) Approx.8,400 r/min

8) MTBF

• 125,000 POH at an operating duty of 10% at room temperature.

• DOS 3.1 or Higher

• Windows 95/98/2000/ME/XP

• OS/2 Warp (Ver 3.0)

• Solaris Ver 2.4 or higher

• Linux Slackware Ver 2.3

• Windows NT 4.0 or later

4. DRIVE PERFORMANCE

1) Data Transfer Rate

* Sustained Data Transfer Rate ..........................................300 Kbytes/s (2x)

600 Kbytes/s (4x) 1,200 Kbytes/s (8x) 1,800Kbytes/s(12x) 2,400Kbytes/s(16x) 3,600 Kbytes/s(24X) 2,700 to 6,000 Kbytes/s 18 to 40x CAV

* Burst Data Transfer Rate (ATAPI) ....................................16.67 Mbytes/s (PIO Mode 4)

16.67 Mbytes/s (MULTI-DMA Mode 2)

2) Average Access Time

Random Access ..................................................................110 ms Typical (Max.40X) : INCLUDING LATENCY

3) Data Buffer Capacity ...........................................................8 Mbytes

5. POWER REQUIREMENTS

1) Voltage

+5 V DC with +5% tolerance, less than 100 mVp-p Ripple voltage +12 V DC with +5% tolerance, less than 100 mVp-p Ripple voltage

2) Current

• Hold Track State ...............................................................+5V DC 1.4A, +12V DC 0.5A (Typical)

• Seeking & Spin up ............................................................+5V DC 1.4A, +12V DC 0.9A (Typical)

6. AUDIO PERFORMANCE

* GCE-8240B FUNCTION TABLE

Item Typical Limit Test Signal Test Condition Note

Output Level

0.7 Vrms

10 % 1KHz 0 dB No Filter at 47 kΩ

S/N 85 dB 75 dB 1KHz 0 dB with IHF-A + 20KHz LPF at 47kΩ

THD 0.08 % 0.1 % 1KHz 0 dB with IHF-A + 20KHz LPF at 47kΩ

Channel

65 dB 60 dB 1KHz 0 dB with IHF-A + 20KHz LPF at 47kΩ

Separation

Frequency +

2dB

Response

AUDIO OUT

3 dB 20Hz~20KHz 0 dB No Filter at 47 kΩ

Funtion GCE-8240B

• CD-R Writing speed 8x/12x/16x/16x-24x ZCLV Data writing

• CD-RW Writing speed 2x/4x/10x Data writing

• CD-ROM Reading speed 40x Data transfer

MODEL

LOCATION OF CUSTOMER CONTROLS

1. Disc tray

This is the tray for the disc. Place the disc on the ejected disc tray, then lightly push the tray (or push the eject button) and the CD will be loaded. NOTE: Don’t pull out or push in the disc tray forcibly. This might cause damage to the loading section of the drive.

2. Stop/Eject button

This button is pressed to open the CD tray. This button works only when power is supplied to the drive. If an Audio CD is playing, pressing this button will stop it, and pressing it again will open the tray.

3. Emergency Eject Hole

Insert a paper clip here to eject the Disc tray manually or when there is no power.

4. Volume control

This is used to adjust the output volume of the headphone jack. It can’t be used to adjust the output volume for the audio output connectors on the rear panel. NOTE : Turn the volume down before turning on the power. Sudden loud noises can damage your hearing.

5. Headphone jack

This jack is for connecting headphones or minispeakers.

6. Drive activity indicators

Two colored LEDs are used to indicate the operation of CD-R/RW Drive. (1) Read The orange color is displayed when the spindle motor begins the Spin up operation: accessing data, reading data, playing Audio, and up loading tray. (2) Write The green color is flashed during disc writing sessions.

READ

WRITE

Headphone Jack

Volume Control

Drive Activity Indicators

Stop/Eject Button

Disc Tray

Emergency Eject Hole

Front Panel

1. Power Connector

Connects to the power supply (5-and 12-V DC) of the host computer. NOTE : Be careful to connect with the proper polarity. Connecting the wrong way may damage the system (and is not guaranteed). Usually this connector can only be attached one-way.

2. IDE Interface Connector

Connect to the IDE (Integrated Device Electronics) Interface using a 40-pin flat IDE cable. NOTE : Do not connect or disconnect the cable when the power is on, as this could cause a short circuit and damage the system. Always turn the power OFF when connecting or disconnecting the cable.

3. Jumper Connector

This jumper determines whether the drive is configured as a master or slave. Changing the master-slave configuration takes effect after power-on reset.

4. Analog Audio Output Connector

Provides output to a sound card (analog signal). Generally you need this to play a regular audio CD.

5. Digital Audio Output Connector

Provides output to a sound card (digital signal).

Digital Audio Output Connector

Jumper Connector

Analog Audio Output Connector

IDE Interface Connector

Power Connector

Rear Panel

1. CABINET and CIRCUIT BOARD DISASSEMBLY

1-1. Bottom Chassis

A. Release 4 screws (A) and remove the Bottom Chassis

in the direction of arrow (1). (See Fig.1-1)

1-2. Front Bezel Assy

A. Insert and press a rod in the Emergency Eject

Hole and then the CD Tray will open in the direction of arrow (2).

B. Remove the Tray Door in the direction of arrow

(3) by pushing the stoppers forward.

C. Release 3 stoppers and remove the Front Bezel Assy.

1-3. Cabinet and Main Circuit Board

A. Remove the Cabinet in the direction of arrow (4).

(See Fig. 1-3)

B. Release 2 hooks (a) and remove the CD Tray

drawing forward.

C. Remove the Main Circuit Board in the direction of

arrow (5).

D. At this time, be careful not to damage the 4

connectors, are positioned at right side, of the Main Circuit Board.

2. MECHANISM ASSY DISASSEMBLY

2-1. Pick-up Unit

A. Release screws (B). B. Separate the Pick-up Unit in the direction of arrow (6).

(4)

(5)

Main Circuit Board

Hooks (a)

Cabinet

(A)

(1)

Bottom Chassis

Fig. 1-1

Fig. 1-2

DISASSEMBLY

Fig. 1-3

Mechanism Assy

Pick-up Unit

(B)

(6)

Fig. 2-1

(3)

Stoppers

Emergency Eject Hole

(2)

Tray Door

Front Bezel Assy

CD Tray

2-2. Pick-up

A. Release 2 screws (C) and remove the Pick-up.

Pick-up Unit

Pick-up

(C)

Fig. 2-2

ATIP Absolute Time in Pre-groove. With an additional modulation of the “Wobble”, the “Groove” contains a time

code information.

Wobble The pre-groove in the Disc is not a perfect spiral but is wobbled.

With : – A typical amplitude of 30 nm

– A spatial peried of 54~64 µm

CW Continuous Wave. The laser light output is at a constant level.

DOW Direct Over-Write. The action in which new information is recored over previously recorded information in

CD-RW disc.

Overwrite

The action in which new information is recorded over previously recorded information.

(Pre-)Groove

The guidance track in which clocking and time code information is stored by means of an FM modulated wobble.

Land Land is characterized in the following way:

When radial signals are concerned,land is defined as the area between the grooves. When HF signal are concerned,land is defined as the area between the marks(pits) in tangential direction.

Hybrid Disc A Multisession disc of which the first Session is mastered. On a hybrid disc, recorded and

mastered information may co-exist.

Mastered Information,stored as pits on the disc during the manufacturing process of the disc. Information (when making the master)

OPC Optimum Power Control. Procedure is determined optimum recording power according to CD-

R/RW Media in recording start step.

ROPC Running OPC. The purpose is to continuously adjust the writing power to the optimum power

that is required. When the optimum power may change because of changed conditions of disc and change in operating temperature.

Jitter The 16 value of the time variation between leading and trailing edges of a specific (I3 … I11) pit

or land as measured by Time Interval Analysis.

Deviation The difference between a fixed value of Pit length and Land length.

TOC Table Of Contents : in the Lead-in Area the subcode Q-channel contains information about the

Tracks on the disc.

Packet A method of writing data on a CD in small increments. Writing Two kinds of packets can be written : Fixed-length and Variable-length.

Write The shape of the HF write signal used to modulate the power of the laser. Strategy The Write Strategy must be used for recordings necessary for disc measurements.

Information Wobble, ATIP, Disc Identification, Write Power, Speed Range OPC Parameters, etc are Area recorded in the Information area of CD-RW Disc

Finalization The action in which (partially) unrecorded or logically erased tracks are finished and the Lead-in

and/or Lead-out areas are recorded or overwritten with the appropriate TOC subcode.

Logical Erase

A method to remove information from a disc area by overwriting it with an EFM signal containing mode 0 subcode A logically erased area is equivalent to an unrecorded

Physical Erase

The action in which previously recorded information is erased by overwriting with a CW laser output. After a Physical Erase action, the erased area on the CD-RW disc is in the unrecorded state again.

Session

An area on the disc consisting of a Lead-in area, a Program area, a lead-out area.

Multi session

A session that contains or can contain more than one session composed Lead-in and Lead-out

GLOSSARY

The differences of CD-R/CD-RW discs and General CD-ROM

1. Recording Layer

Recordable CD has a wobbled pre-groove on the surface of disc for laser beam to follow track.

2. Disc Specification

Read-only Disc

CD-R and CD-RW Disc

3~11T

1.6um

0.4~0.5 um

(Pit)Groove

Land

Track pitch(p)

Radial Direction

Groove

Land

Radial Error Signal

The Groove wobble

Average center

Actual center

CD-ROM CD-R CD-RW

Standard Yellow Book Orange Book II Orange Book III

Record Not available Write once Re-writable

I 11/Itop

> 0.6 > 0.6 0.55 > M11> 0.70

(HF Modulation)

Write Laser Power(mW) 10-30 mW 6-25 mW

Read Laser Power(mW) < 0.5 mW < 0.7 mW < 1.0 mW

Jitter < 35 nsec < 35 nsec < 35 nsec

Reflectivity (R

top) 70 % 65 % 15 % ~ 25 %

CD-ROM (READ-ONLY DISC)

a=30nm

3. Disc Materials

1) CD-ROM disc

Laser Beam

Groove

Substrate (Polycarbonate)

Organic Dye Layer

Reflective Layer

Protective Layer

Label Printing

2) CD-R disc

Pigment Reflective Layer Color

Phtalocyanine Gold/Silver Yellow/White

Cyanine Gold/Silver Dark Green/Bright Green

Azo Gold/Silver Dark Blue

• It is composed of Silver _ colored aluminum plate and Reflective layer.

• Groove (Pit) of aluminum plate make a track.

• Laser wavelength : 780 nm, Laser Power (Read): 0.5mW

• Signal is detected by the difference of reflective beam intensity between “pit” and “Land” on the disc.

• It is so-called WORM (Write Once Read Many) CD.

• It is composed of polycarbonate layer, Organic dye layer, Reflective layer, and Protective layer.Gold/Silver Reflective layer is used to enhance the reflectivity

• According to the kinds of Organic dye layer, it is divided by Green CD, Gold CD, Blue CD.

• Laser Wavelength : 780 nm, Laser Power (read) : 1.2 mW

• Recording Power : 8x(9~30mW), 12x(12~38mW), 16x(14~44mW), 24x(18~50mW)

• When some part of dye layer is exposed to laser heat, it’s color changs black.Therefore, writing and reading is enabled by the difference of reflectivity between changed part and unchanged part.

• Polycarbonate layer has Pre_Groove which make a Track.

Laser Beam

Pit

Substrate (Polycarbonate)

Reflective Layer

Protective Layer

Label Printing

3) CD-RW Disc

Reading process of Optical Disc

Laser Beam

Groove

Substrate (Polycarbonate)

Reflective Layer

Dielectric Layer(TL)

Dielectric Layer(UL)

Protective Layer

Label Printing

• It is composed of polycarbonate layer, alloy(silver, arsenic) layer, aluminum reflectivity layer, protective layer.

• An crystalized alloy layer is transformed into noncrystalized by the laser heat. Therefore, writing and reading

is enabled by the difference of reflectivity.

• It is possible to overwrite about 1000 times.

• Laser Wavelength : 780 nm, Laser Power (Read) : 1.0mW

• Recording Power : Erase (4~18mW), Write (15~40mW)

• When disc rewriting, new data is overwritten previously recorded data.

• Polycarbonate layer has a Pre-Groove which make a track.

Lens

Beam Spot

Focusing Lens

Laser Spot at Constant Read Intensity

Reflected Light Signal

Laser Spot Position (Time)

Previously Recorded Marks

Groove Land Mirror

top

Numerical aperture: NA=nsinθ,

n: Refractive index

Focus depth : H =

/NA

laser spot diameter : D =

/NA

5. Writing Process of CD-R Disc

a b c d e f g

Incident Laser Powe r

(Read)

(Write)

Laser Spot Position (Time)

a b c d e f g

Laser Spot Position (Time)

Laser Spot

Recorded Mark

Reflected Light Signal

Below "ORP"– Mark Too Short

At Optimum Record Power ("ORP")

Above "ORP" – Mark Too Long

Time

6. Writing process of CD-RW Disc

Write Power

Erase Power

Read Power

Groove

Crystal

Amorphous

Recorded state

(lower reflectivity)

Melting/

quenching

Heating/

gradual cooling

Crystal phase

Erased state

(higher reflectivity)

7. Organization of the PCA, PMA and Lead-in Area

1) Layout of CD-ROM disc

Center hole Clamping and Label Area Information Area

Lead-in Area

Diameter 15 mm

Diameter 46 mm

Diameter 120 mm

Program Area

Read Only Disc

Lead-out Area

Program Area Lead-out Area

Center hole

Clamping and Label Area

Information Area

PCA PMA

Test Area Count Area

Diameter 15 mm

Diameter 45 mm

Diameter 120 mm

Unrecorded Disc

Tsl-00:35:65 Tsl-00:15:05

Tsl-00:13:25

Tsl

99:59:74 00:00:00

in out

Test Area : for performing OPC procedures.

Count Area : to find the usable area immediately in T.A

Tsl : start time of the Lead-in Area, as encoded in ATIP

PMA : Program Memory Area

Disc Center

2) Layout of CD-R/RW disc

8. Function of PCA and PMA area

1) PCA (Power Calibration Area)

• PCA area is used to determine the correct Laser Power for a disc.

– Method 1 : PCA area is divided by a track. – Method 2 : The previous Calibration value is referred. – Method 3 : ROPC is used to determine Laser Power value automatically in data writing.

• CD-R Disc can write maximum 99 Tracks but CD-RW Disc can write unlimited tracks because it has a rewritable

function.

2) PMA (Program Memory Area)

• It has a track information (track No, track Start/End time) of every track before writing completed.

– PMA area has the last written point and the next writable point of a disc. – In case of CD to CD copy, some writer may not write PMA area.

* When Disc is Finalized,

PMA information is transferred to the Lead_In area so that general Driver can read it.

* Because PCA and PMA area exist before Lead-In area, General CD Player or CD-ROM Drive can’t read

these areas.

9. OPC and ROPC

1) OPC (Optimum Power Control)

• This is the first step of writing process, because CD writer has its own laser power value and media have different writing characteristics,

– This is determined by the Writing characteristic, speed, temperature, and humidity. – Laser wavelength is determined by the environmental temperature (775~795nm) and Optical Laser Power is

determined by the test and retry.

• Asymmetry and optimum writing Power

– EFM signal Asymmetry is determined by the writing power.

Therefore, Optical Power which has the same value to the preset power value can be estimated by measuring HF signal Asymmetry on the PCA area.

• Measurement of Asymmetry

* Parameter setting (Beta) : Using AC coupled HF signal before equalization

Beta = (A1+A2)/(A1-A2)

Time

P << Po

Time

P = Po

HF Signal

Time

P >> Po

2) ROPC (Running Optimum Power Control)

• Variable primary factor of Optimum Power

– Change of Power sensitivity on the Disc. (limited to 0.05 *Po) – Wavelength shift of the laser diode due to the operating temperature change. – Change of the Spot aberration due to the Disc skew,

Substrate thickness, Defocus.

– Change of Disc or Optics conditions due to the long term OPC

==> It is necessary to adjust continuously to obtain the Optimum Power.

• Principle of Running OPC

– To meet the factors mentioned above,

a horizontal _ direction movement of a curve is uesd.

– Beta = f(B-level) = constant on the Recorded Disc – Procedure of ROPC

a. Reference B-level is determined during OPC Procedure. b. During Recording, B-level value is controlled to have a close

Reference B-level value.

c. Normalization of B-level is used to eliminate the effect of reflectivity fluctuation.

==> The reflected B-level value is normalized by the disc reflectivity itself.

CD-R/RW Media

Write Strategy Determination

PCA Test Area

Program Area

PMA Area

Lead-In Area

Lead-out Area

OPC

PCA Count Area

ROPC

* Recording Capacity of CD-R/RW (74Minute Recording media)

• (2048 Byte/Sector) X (75 Sector/Second) X (60 Second/Minute) X 74 Minute = 681,984,000 Bytes = 682 Mbytes

• But the actual recording capacity is about 650 Mbytes. (according to the ISO 9660 standard, approximately 30 Mbytes are used to make directory structure and volume names.)

Incident recording pulse

Reflected recording pulse

Sampled timing B

11T

Sample B-level (Write Power)

Level B

Sampled at timing B

Pwo decided by OPC

Recording Power

Level B with Pwo

normalized to recording power

Sample Disc Reflectivity (Read power)

10. Writing Process of DISC

INTERNAL STRUCTURE OF THE PICK-UP

1. KRS-310B Circuit Diagram

1 2 3

4 5

1 2

3 4

5 6 7 8

10 11 12

10 9 8 7 6

VR1

VR2

R6 R7

C10 C9 C8

Vcc

2 Axis Actuator

IC1 PDIC

IC2 FPDIC

R11

R12

R10

GND

GNDGND

VccVc

BinOUT

PDIN

VOUT

VCC

VREF

VCC

GND

IOUT

IINR

IOUT

IIN2

GND

IIN3

GND

RFREQ

RAMP

GND

ENABLE

GND

OSCEN

WEN3

VCC

WEN2

GND

7 8 9

10 11

12 13 14 15 16 17 18 19 20 21 22 23 24 25 26

27 28 29 30 31 32

FCS +

FCS -

TRK +

TRK -

G D

C E

RF SUM

PDGND

PDVC

F B A H

PDVCC

FPDO FPDVCC FPDGND

FPDVC LDVCC

LDVCC

VRDC

VWDC1 VWDC2 LDGND

LDGND

WE1

WE2

OSCEN

33 34

ENBL

MODAMP

IC3 LD Driver

2. Signal detection of the P/U

1) Focus Error Signal ==> (A+C)-(B+D)

This signal is generated in RF IC (IC401 : CXA2638R) and controls the pick-up’s up and down to focus on Disc.

2) Tracking Error Signal (DPP Method) ==> {(A+D)-(B+C)}- kx {(F+H)-(E+G)}

This signal is generated in RF IC (IC401 : CXA2638R) and controls the pick-up’s left and right shift to find to track on Disc.

3) RF Signal ==> (A+B+C+D)

This signal is converted to DATA signal in DSP IC (IC201 : OTI-9797).

Pick-Up module

Photo Diode

Tracking

Focusing

Infrared Iaser

k[(F+H) - (E+G)]

(A+D) - (B+C)

(A+D) - (B+C) - k[(F+H) - (E+G)]

Offset

Sub2

Main

Tp/2

Sub1

Track Center

F, E

D,C

A,B

H,G

DESCRIPTION OF CIRCUIT

1. ALPC (Automatic Laser Power Control) Circuit

1-1. ALPC Loop Circuit

RFPDG

FPDO

AUX

FVREF

WFPDSH

HOLDSW

WLDON

WR/RE

WGATE

WR/RE

WGATE

EFM1

EFM2

R321

R322

R427

R426

C454

C443

R447

D401

GND

R19

VWDC

WREF

HOLDTC

ODREF

APCCSW

R18

R408

C432

VWDCN

APCCSW

WREFSE

S3.

R14

25.8K

R15

25.8K

GND

R12

R10 5K

R6 20K

20K

R8 20K

10K

GND

SCLK

DACS

WREFSE

C445

R252

R247

R429

SHOUT

RFPDSH

20dB/26dB

3.3V

R422

R423

IC403

IC205

IC301 MICOM

IC201

OTI-9797

C456

C455

MPXOUT

(testmode)

MPXOUT

(testmode)

VRDCN

VRDC

R16

R17

R410

C433

R11 10K

GND

RREFSE

R9 5K

R1 20K

20K

A:OFF B:ON

A:OFF

L:B.HOLD H:A.SAMPLE

B:ON

RREF

WREF

ODREF

SHOUT

WRITEG WFPDG

DAC

GNDTyp. 10mV/step sbit

GND

Typ. 10mV/step 8 bit

Typ. 10mV/step 7 bit

H:RREF

R13

R7 20K

(Read)

(Write)

20K

25.8K

GND

L:OPEN

H:OPEN L:WREF

RLDON

ERCNT

GND

100

166

188

180

183

184

6564

PN401 P/U

TC7W08FV

IC401 CXA2638R

FPDVC

FPDO

VRDC

VWDC

VWDC2

WE1

WE2

S/H

Gain

adj.

IC402

DAC

S/H

1-2. ALPC(Automatic Laser Power Control) Circuit Operation

This circuit consists of Feedback Loop to maintain light output of the Laser Diode(FPDO). Feedback signal, output voltage from PD(Photo Detector) of P/U, is used monitor the light power of Laser Diode.

1) Read Loop

RREF(Read Reference Voltage) of IC401(CXA2638R) Pin 96, which is from DAC(IC403) Pin 18, is the reference level of the Read Loop part of this ALPC Circuit.

• When Playback

VRDC(Pin 97) signal of IC401(CXA2638R) is output to P/U through Gain Control S/W and drives Laser Diode during play back. This S/W Ciruit is designed to reduce transition time from CD-RW writing mode to playback mode.

• When writing mode

- CD-R Three Laser Power Levels, Read, Write, and Overwrite, are used to write on CD-R disc, and Read

Level is used to monitor the output laser power. For stabilizing read loop, the S/H signal(RFPDSH), which sample and hold the Read Level of laser power in the CD-R writing mode, is input through Pin 32 of IC401(CXA2638R).

- CD-RW

Three Laser Power Levels, Read, Erase and Write, are used to write on CD-RW disc, and Erase Level is used, during CD-RW writing, to monitor output laser power. It is not VRDC but VWDC that is the output signal of the control loop performed by Erase level.

2) Write Loop

For stabilizing write Loop, the S/H signal(WFPDSH), which sample and hold the Erase Level of laser

power in the CD-RW writing mode, is input through Pin 31 of IC401(CXA2638R).

Output voltage of Write Loop, VWDC(Pin 93 of IC401(CXA2638R)), is protected by the high limit diode

applied to P/U.

2. RF Amplifier Circuit

Block Diagram

A,B,C,D

E,F,G,H

RFSUM

PDIC

GND

Vcc

CXA2638R (IC401)

IC201

OTI9797

Pick up

KRS-310B

Gain Amp

59 197

Offset adj

R6R5

R403

C417

R404

Vref

Main S/H Gain adj Offset adj

CEM

CEO

CEP

198

204

EQRFP

C223

EFM

163

ATFG

WOBBLE

132

Limit

Gain

Amp.

Side

S/H

SPPO

4((F+H)-(E+G))

MPP 2(A+D)-(B+C))

DVC

Gain

adj

Gain

adj

Offset

adj

LPF

(40KHz)

Gain

adj

offset

adj

Limit

GCA HPF

HPF AGC BPF AGC

Slice

circuit

HPF

EQ HPF

636567

x0.25 x5 x3.2

3. Focus/Tracking/Sled Servo Circuit

3-1. Focus, Tracking & Sled Servo Process

Focus, Tracking Servo

Pick- up

A,B,C,D,E,F,G,H

A,B,C,D

Focus Error Detector

Detector

Track Error

A,B,C,D E,F,G,H

IC401 CXA2638R

TE FE

A/D

Low freq Gain Filter

Ditital EQ

DAC

Sled Control

Signal

A/D

IC201 Servo Control OTI9797

LEVEL SHIFT

Tracking Focusing Actuator

FAO

TAO

SLO

F+

F-

T+

T-

Sled Control

SLED MOTOR

LEVEL SHIFT

SM_A-

IC501 BD7902C

SM_A+

SM_B+

SM_B-

IC501 BD7902C

IC402 BU2500FV (DAC)

3-2. Focus Servo

The aim of Focus Servo is to maintain the distance between object lens of P/U and disc surface, so that the detected RF signals (A, B, C, D) can be maximized. Focus Servo is based on focus error (FE) signal which is generated from focus error detection block in CXA2638R(IC401) using Astigmatism Method. Focus gain and path can be changed at the CXA2638R according to the disc, and the resulting output (FE) is input to Servo IC (IC201, OTI9797). FE signal after first amplification in OTI9797 is A/D converted and input to Digital Equalizer Block, most important part at the Focus Servo. At the Digital Equalizer, adjustments for Focus Bias and Loop Gain are performed. After D/A converted, Focus servo signal is output through FOO port (OTI9797, Pin207) and drive Focus Actuator through the Focus Drive IC (IC501, BD7902C).

3-3. Tracking Servo

The aim of Tracking Servo is to make laser beam trace the data track on disc. Tracking Error (TE) signal is generated from tracking error detection block in CXA2638R (IC401) using DPP (Differential Push-Pull) Method. DPP method uses not only main beam (A, B, C, D) but side beams (E,F and G, H) for correcting DC offset generated in Push-Pull method. The remaining procedures of TE signal processing in CXA2638R is similar to Focus Servo. After D/A converted, Tracking servo signal is output through TRO port (OTI9797, Pin208) and drive Tracking Actuator through the Tracking Drive IC (IC501, BD7902C).

3-4. Sled Servo

The working distance of tracking actuator is too short to cover whole disc radius. Sled Servo make PU move by little and little so that the laser beam keep tracing the data track on disc continuously when tracking actuator reaches the working limit. Another function of Sled Servo is to seek a target point on disc, following user commands. Sled control signal, STEP-CTRL0,1 from BU2500FV is generated in µ-com, STEP-CTRL0,1 are output to sled motor via IC501(BD7902C).

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LG GCE-8240B Service Manual

Specifications and Main Features

Frequently Asked Questions

User Manual