LG GT540 User manual

Service Manual Model : GT540
Internal Use Only
Service Manual
GT540
Date: April, 2010 / Issue 1.0

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Copyright © 2010 LG Electronics. Inc. All right reserved.
Only for training and service purposes
LGE Internal Use Only
Table Of Contents
1. Introduction ...................................................5
1.1 Purpose......................................................................5
1.2 Regulatory Information.................................................5
2. performance................................................... 7
2.1 Product Name .............................................................7
2.2 Supporting Standard....................................................7
2.3 Main Parts : GSM Solution ...........................................7
2.4 HW Features ...............................................................8
2.5 SW Features .............................................................10
2.6 HW SPEC. ................................................................13
3. TECHNnICAL BRIEF....................................... 19
3.1 GENERAL DESCRIPTION.............................................19
3.2 GSM MODE...............................................................21
3.3 UMTS MODE.............................................................23
3.4 GPS RECEIVER ..........................................................26
3.5 LO GENERATION and DISTRIBUTION CIRCUIT ..............27
3.6 OFF-CHIP RF COMPONENTS......................................28
3.7 Digital Baseband(DBB/MSM7227) ..............................34
3.8 Hardware Architecture ...............................................35
3.9 Subsystem (MSM7227) .............................................39
3.10 Power Block............................................................42
3.11 External memory interface .......................................48
3.12 H/W Sub System .....................................................50
3.13. Audio and sound.....................................................58
3.14 Display ...................................................................65
3.15 Motion Sensor.........................................................67
3.16 Vibrators .................................................................68
3.17 Compass Sensor .....................................................69
3.18 Main Features.........................................................70
4. Trouble Shooting.......................................... 78
4.1 RF Component ..........................................................78
4.2 SIGNAL PATH ............................................................80
4.3 Checking TCXO Block ................................................84
4.4 Checking GSM TX Module(GSM PAM+FEM) BLOCK.....86
4.5 Checking WCDMA Block ............................................89
4.6 Checking GSM BLOCK...............................................99
4.7 GPS/WIFI/BT RF COMPONENTS................................104
4.8 GPS/WIFI/BT Trouble shooting ..................................106
4.9 Power ON Troubleshooting .......................................109
4.10 Charger Troubleshooting ........................................113
4.11 USB trouble...........................................................116
4.12 Audio trouble.........................................................119
4.13 3M AF Camera trouble...........................................129
4.14 Main LCD trouble ..................................................132
4.15 SIM Detect Troubleshooting....................................134
4.16 Side Key Troubleshooting .......................................136
4.17 VIBRATOR .............................................................138
4.18 Motion Sensor on/off trouble ..................................140
4.19 Compass Sensor on/off trouble ..............................142
5. Download ................................................... 144
6. Block diagram............................................157
7. Circuit Diagram..........................................165
8. BGA Pin Map ..............................................177
9. PCB Layout................................................. 181
10. Calibration & RF Auto Test Program
(Tachyon).................................................. 191
12. Exploded view & Replacement part list .207
12.1 Exploded view .......................................................207
12.2 Replacement Parts ................................................209
12.3 Accessory .............................................................235

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LGE Internal Use Only Copyright © 2010 LG Electronics. Inc. All right reserved.
Only for training and service purposes

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Copyright © 2010 LG Electronics. Inc. All right reserved.
Only for training and service purposes
LGE Internal Use Only
1. Introduction
1. Introduction
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ͽ͸ͶͺΟΥΖΣΟΒΝΆΤΖ΀ΟΝΪ
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1. INTRODUCTION
1.1. Purpose
This manual provides the information necessary to repair, calibration, description and download the features of this
model.
1.2. Regulatory Information
A. Security
Toll fraud, the unauthorized use of telecommunications system by an unauthorized part (for example, persons other
than your company’s employees, agents, subcontractors, or person working on your company’s behalf) can result in
substantial additional charges for your telecommunications services. System users are responsible for the security of
own system. There are may be risks of toll fraud associated with your telecommunications system. System users are
responsible for programming and configuring the equipment to prevent unauthorized use. The manufacturer does
not warrant that this product is immune from the above case but will prevent unauthorized use of common carrier
telecommunication service of facilities accessed through or connected to it. The manufacturer will not be
responsible for any charges that result from such unauthorized use.
B. Incidence of Harm
If a telephone company determines that the equipment provided to customer is faulty and possibly causing harm
or interruption in service to the telephone network, it should disconnect telephone service until repair can be done.
A telephone company may temporarily disconnect service as long as repair is not done.
C. Changes in Service
A local telephone company may make changes in its communications facilities or procedure. If these changes could
reasonably be expected to affect the use of the phones or compatibility with the net work, the telephone company
is required to give advanced written notice to the user, allowing the user to take appropriate steps to maintain
telephone service.

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LGE Internal Use Only Copyright © 2010 LG Electronics. Inc. All right reserved.
Only for training and service purposes
1. Introduction
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ͽ͸ͶͺΟΥΖΣΟΒΝΆΤΖ΀ΟΝΪ
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D. Maintenance Limitations
Maintenance limitations on the phones must be performed only by the manufacturer or its authorized agent. The
user may not make any changes and/or repairs expect as specifically noted in this manual. Therefore, note that
unauthorized alternations or repair may affect the regulatory status of the system and may void any remaining
warranty.
E. Notice of Radiated Emissions
This model complies with rules regarding radiation and radio frequency emission as defined by local regulatory
agencies. In accordance with these agencies, you may be required to provide information such as the following to
the end user.
F. Pictures
The pictures in this manual are for illustrative purposes only; your actual hardware may look slightly different.
G. Interference and Attenuation
A phone may interfere with sensitive laboratory equipment, medical equipment, etc. Interference from
unsuppressed engines or electric motors may cause problems.
H. Electrostatic Sensitive Devices
ATTENTION
Boards, which contain Electrostatic Sensitive Device (ESD), are indicated by the sign. Following information is
ESD handling:
• Service personnel should ground themselves by using a wrist strap when exchange system boards. • When repairs
are made to a system board, they should spread the floor with anti-static mat which is also grounded.
• Use a suitable, grounded soldering iron. • Keep sensitive parts in these protective packages until these are used.
• When returning system boards or parts like EEPROM to the factory, use the protective package as described.

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Copyright © 2010 LG Electronics. Inc. All right reserved.
Only for training and service purposes
LGE Internal Use Only
2. Performance
2. Performance
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ͽ͸ͶͺΟΥΖΣΟΒΝΆΤΖ΀ΟΝΪ
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2. PERFORMANCE
2.1 Product Name
GT540 : WCDMA900/2100+EGSM/GSM850/DCS/PCS
(HSDPA 7.2Mbps GPRS Class 12 / EDGE Class 12)
2.2 Supporting Standard
Item Feature Comment
Supporting Standard WCDMA(FDD1,8)/EGSM/GSM850/DCS1800/PCS1900
with seamless handover
Phase 2+(include AMR)
SIM Toolkit: Class 1, 2, 3, C-E

Frequency Range WCDMA(FDD1) TX : 1920 – 1980 MHz
WCDMA(FDD1) RX : 2110 – 2170 MHz
WCDMA(FDD8) TX : 880 – 915 MHz
WCDMA(FDD8) RX : 925 – 960 MHz
EGSM TX: 880 – 915 MHz
EGSM RX: 925 – 960 MHz
GSM850 TX: 824 – 849 MHz
GSM850 RX: 869 – 894 MHz
DCS1800 TX : 1710 – 1785 MHz
DCS1800 RX: 1805 – 1880 MHz
PCS1900 TX: 1850 – 1910 MHz
PCS1900 RX: 1930 – 1990 MHz

Application Standard JAVA 2.0 
2.3 Main Parts : GSM Solution
Item Part Name Comment
Digital Baseband MSM7227 : Qualcomm 
Analog Baseband PM7540 : Qualcomm 
RF Chip RTR6285 : Qualcomm 

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LGE Internal Use Only Copyright © 2010 LG Electronics. Inc. All right reserved.
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2. Performance
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2.4 HW Features
Item Feature Comment
Form Factor Bar type 
1) Capacity
Standard : Li-Ion polymer, 1500mAh

Battery
2) Packing Type : Soft Pack 
Size Standard :
109 x 54.5 x 12.9 mm

Weight 115.5g With Battery 
Volume TBD 
PCB All Layer (10) , 0.8t 
Stand by time 2G Up to 350 hrs
3G Up to 3500 hrs
@ Paging Period 5 (2G)
@ DRX 7 (3G)
Charging time 3 hrs @ Power Off / 1500mAh
Talk time 2G Up to 250mins
3G Up to 250mins
@ Power Level 5 (2G)
@ Tx = 12dBm (3G)
RX sensitivity
WCDMA(FDD1) : -106.7 dBm
WCDMA(FDD8) : -103.7 dBm
EGSM : -105 dBm
GSM850 : -105 dBm
DCS 1800 : -105 dBm
PCS 1900 : -105 dBm

WCDMA/
GSM/
GPRS
WCDMA : 24dBm/3.84MHz,+1/-3dBm
EGSM : 33dBm
GSM850 : 33 dBm
DCS 1800 : 30 dBm
PCS 1900 : 30 dBm
Class3(WCDMA)
Class4 (EGSM)
Class4 (GSM850)
Class1 (PCS)
Class1 (DCS)
TX
output
power
EDGE
GSM 900 : 27 dBm
DCS 1800 : 26 dBm
PCS 1900 : 26 dBm
E2 (GSM900)
E2 (PCS)
E2 (DCS)
GPRS compatibility GPRS Class 12 
EDGE compatibility EDGE Class 12 
SIM card type Plug-In SIM
3V /1.8V

Display Main LCD
TFT Main LCD(3’, 320 x 480)
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Built-in Camera 3M CMOS Camera 
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ͽ͸ͶͺΟΥΖΣΟΒΝΆΤΖ΀ΟΝΪ
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2.4 HW Features
Item Feature Comment
Form Factor Bar type 
1) Capacity
Standard : Li-Ion polymer, 1500mAh

Battery
2) Packing Type : Soft Pack 
Size Standard :
109 x 54.5 x 12.9 mm

Weight 115.5g With Battery 
Volume TBD 
PCB All Layer (10) , 0.8t 
Stand by time 2G Up to 350 hrs
3G Up to 3500 hrs
@ Paging Period 5 (2G)
@ DRX 7 (3G)
Charging time 3 hrs @ Power Off / 1500mAh
Talk time 2G Up to 250mins
3G Up to 250mins
@ Power Level 5 (2G)
@ Tx = 12dBm (3G)
RX sensitivity
WCDMA(FDD1) : -106.7 dBm
WCDMA(FDD8) : -103.7 dBm
EGSM : -105 dBm
GSM850 : -105 dBm
DCS 1800 : -105 dBm
PCS 1900 : -105 dBm

WCDMA/
GSM/
GPRS
WCDMA : 24dBm/3.84MHz,+1/-3dBm
EGSM : 33dBm
GSM850 : 33 dBm
DCS 1800 : 30 dBm
PCS 1900 : 30 dBm
Class3(WCDMA)
Class4 (EGSM)
Class4 (GSM850)
Class1 (PCS)
Class1 (DCS)
TX
output
power
EDGE
GSM 900 : 27 dBm
DCS 1800 : 26 dBm
PCS 1900 : 26 dBm
E2 (GSM900)
E2 (PCS)
E2 (DCS)
GPRS compatibility GPRS Class 12 
EDGE compatibility EDGE Class 12 
SIM card type Plug-In SIM
3V /1.8V

Display Main LCD
TFT Main LCD(3’, 320 x 480)

Built-in Camera 3M CMOS Camera 

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Copyright © 2010 LG Electronics. Inc. All right reserved.
Only for training and service purposes
LGE Internal Use Only
2. Performance
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ͽ͸ͶͺΟΥΖΣΟΒΝΆΤΖ΀ΟΝΪ
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Status Indicator No 
Keypad Function Key : 2
Side Key : 2
Function Key:
CAM, Search
Side Key :
Volume up/down
ANT Main : Internal Fixed Type 
System connector 5 Pin 
Ear Phone Jack 3.5Phi, 4 Pole, Stereo 
PC synchronization No 
Memory NAND Flash : 4Gbit
SDRAM : 2Gbit

Speech coding FR, EFR, HR,AMR 
Data & Fax Built in Data & Fax support 
Vibrator Built in Vibrator 
Blue Tooth V2.1+ EDR 
MIDI(for Buzzer
Function) SW Decoded 72Poly 
Music Player MP3/ WMA/AAC/HE-AAC/EAAC+ 
Video Player MPEG4, H.263, H.264, WMV9 
Camcorder MPEG4, H.263, 
Voice Recording Yes 
Speaker Phone mode
Support Yes 
Travel Adapter Yes 
CDROM Yes 
Stereo Headset Yes 
Data Cable Yes 
T-Flash
(External Memory) Yes 

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2. Performance
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ͽ͸ͶͺΟΥΖΣΟΒΝΆΤΖ΀ΟΝΪ
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2.5 SW Features
Item Feature Comment
RSSI 0 ~ 4 Levels 
Battery Charging 0 ~ 6 Levels 
Key Volume 0 ~ 7 Level 
Audio Volume 1 ~ 15 Level 
Time / Date Display Yes 
Multi-Language Yes English/French/German/Spanish/Italia
n/Danish/Dutch/Korean
Quick Access Mode Dialing/ Contact / Menu / Message /
Camera

PC Sync No 
Speed Dial No Voice mail center -> 1 key
Profile Yes not same with feature phone setting
CLIP / CLIR Yes 
Phone Book
Name / Number / Email / Chat Id/
Website/Postal
addresses/Organizations/Groups/
BirthdayNotes / Ringtone
There is no limitation on the number
of items.
It depends on
available memory amount.
Last Dial Number Yes
Last Dial Numbers, Last Received
Numbers and Last Missed Numbers
can store up to a total of 500.
Last Received
Number Yes
Last Dial Numbers, Last Received
Numbers and Last Missed Numbers
can store up to a total of 500.
Last Missed Number Yes
Last Dial Numbers, Last Received
Numbers and Last Missed Numbers
can store up to a total of 500.
Search by Number
/ Name Name 
Group Yes
There is no limitation on the number
of items. It depends on
available memory amount.
Fixed Dial Number Yes 
Service Dial Number No 
Own Number Yes Read only
(add/edit/delete are not
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ͽ͸ͶͺΟΥΖΣΟΒΝΆΤΖ΀ΟΝΪ
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2.5 SW Features
Item Feature Comment
RSSI 0 ~ 4 Levels 
Battery Charging 0 ~ 6 Levels 
Key Volume 0 ~ 7 Level 
Audio Volume 1 ~ 15 Level 
Time / Date Display Yes 
Multi-Language Yes English/French/German/Spanish/Italia
n/Danish/Dutch/Korean
Quick Access Mode Dialing/ Contact / Menu / Message /
Camera

PC Sync No 
Speed Dial No Voice mail center -> 1 key
Profile Yes not same with feature phone setting
CLIP / CLIR Yes 
Phone Book
Name / Number / Email / Chat Id/
Website/Postal
addresses/Organizations/Groups/
BirthdayNotes / Ringtone
There is no limitation on the number
of items.
It depends on
available memory amount.
Last Dial Number Yes
Last Dial Numbers, Last Received
Numbers and Last Missed Numbers
can store up to a total of 500.
Last Received
Number Yes
Last Dial Numbers, Last Received
Numbers and Last Missed Numbers
can store up to a total of 500.
Last Missed Number Yes
Last Dial Numbers, Last Received
Numbers and Last Missed Numbers
can store up to a total of 500.
Search by Number
/ Name Name 
Group Yes
There is no limitation on the number
of items. It depends on
available memory amount.
Fixed Dial Number Yes 
Service Dial Number No 
Own Number Yes Read only
(add/edit/delete are not

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Copyright © 2010 LG Electronics. Inc. All right reserved.
Only for training and service purposes
LGE Internal Use Only
2. Performance

ͽ͸ͶͺΟΥΖΣΟΒΝΆΤΖ΀ΟΝΪ
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supported)
Voice Memo Yes 
Call Reminder No 
Network Selection Automatic 
Mute Yes 
Call Divert Yes 
Call Barring Yes 
Call Charge (AoC) Yes 
Call Duration Yes 
SMS (EMS)
There is no limitation on the
number of items. It depends on
available memory
amount.
EMS does not support.
SMS Over GPRS No 
EMS Melody / Picture No 
Send / Receive / Save No 
MMS MPEG4
Send / Receive / Save Yes 
Long Message MAX 459 characters SMS 3pages
Cell Broadcast Yes 
Download Over the Web 
Game Yes 
Calendar Yes 
Memo Yes
There is no limitation on the number
of items.
It depends on available memory
amount.
World Clock No 
Unit Convert No 
Stop Watch No 
Wall Paper Yes 
WAP Browser No
Support only web browser based on
webkit. WAP stack and wml are not
supported.
Download Melody /
Wallpaper Yes Over web browser

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LGE Internal Use Only Copyright © 2010 LG Electronics. Inc. All right reserved.
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2. Performance

ͽ͸ͶͺΟΥΖΣΟΒΝΆΤΖ΀ΟΝΪ

SIM Lock Yes Operator Dependent
SIM Toolkit Class 1, 2, 3, C 
MMS Yes Google MMS Client
EONS Yes 
CPHS Yes V4.2
ENS No 
Camera Yes 3M AF /
Digital Zoom : x4
JAVA Yes
CLDC V1.1 / MIDP V2.1
Download Over Web
But JAVA is not supported for VDF
and BYT
Voice Dial No 
IrDa No 
Bluetooth Yes Ver. 2.1+EDR
(HSP,HFP,A2DP,AVRCP)
FM radio Yes 
GPRS Yes Class 12
EDGE Yes Class 12
Hold / Retrieve Yes 
Conference Call Yes Max. 6
DTMF Yes 
Memo pad No 
TTY No 
AMR Yes 
SyncML Yes 
IM Yes 
Email Yes 

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Copyright © 2010 LG Electronics. Inc. All right reserved.
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LGE Internal Use Only
2. Performance
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ͽ͸ͶͺΟΥΖΣΟΒΝΆΤΖ΀ΟΝΪ

2.6. HW SPEC.
1) GSM transceiver specification

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2. Performance
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ͽ͸ͶͺΟΥΖΣΟΒΝΆΤΖ΀ΟΝΪ

2) WCDMA transmitter specification

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Copyright © 2010 LG Electronics. Inc. All right reserved.
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LGE Internal Use Only
2. Performance
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ͽ͸ͶͺΟΥΖΣΟΒΝΆΤΖ΀ΟΝΪ

3) WCDMA receiver specification

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LGE Internal Use Only Copyright © 2010 LG Electronics. Inc. All right reserved.
Only for training and service purposes
2. Performance

ͽ͸ͶͺΟΥΖΣΟΒΝΆΤΖ΀ΟΝΪ

4) HSDPA transmitter specification

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Copyright © 2010 LG Electronics. Inc. All right reserved.
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LGE Internal Use Only
2. Performance
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ͽ͸ͶͺΟΥΖΣΟΒΝΆΤΖ΀ΟΝΪ

5) HSDPA receiver specification
6) WLAN 802.11b transceiver specification

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LGE Internal Use Only Copyright © 2010 LG Electronics. Inc. All right reserved.
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2. PERFORMANCE
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ͽ͸ͶͺΟΥΖΣΟΒΝΆΤΖ΀ΟΝΪ

7) WLAN 802.11g transceiver specification
8) GPS receiver specification

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Copyright © 2010 LG Electronics. Inc. All right reserved.
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LGE Internal Use Only
3. TECHNICAL BRIEF
3. TECHNICAL BRIEF
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ͽ͸ͶͺΟΥΖΣΟΒΝΆΤΖ΀ΟΝΪ
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3. TECHNICAL BRIEF
3.1 GENERAL DESCRIPTION
The GT540 supports UMTS-900, UMTS-2100, GSM-850, GSM-850, GSM-900, GSM-1800, and GSM-1900 based
GSM/GPRS/EDGE/UMTS. All receivers and the UMTS transmitter use the radioOne1Zero-IF architecture to eliminate
intermediate frequencies, directly converting signals between RF and baseband. The quad-band GSM transmitters
use a baseband-to-IF upconversion followed by an offset phase-locked loop that translates the GMSK-modulated or
8-PSK-modulated signal to RF.
[Figure 1-1] Block diagram of RF part
LGE Internal Use Only
Challenge 123
RTR6285
PM7540
FRONT
END
MODULE
SKY77544
TX_IP
TX_IN
PRX_IP
PRX_IN
DRX_IP
DRX_IN
TCXO
GCELL_INP
GCELL_INN
EGSM_INP
EGSM_INN
DCS_INP
DCS_INN
GPCS_INP
GPCS_INN
HB_RF_OUT2
HB_RF_OUT3
HB_RF_OUT1
LB_RF_OUT1
LB_RF_OUT2
RF_ON
DAC_IREF
SBDT
TX_BIAS
GPS_IN
WPRXHBP
WPRXHBN
WPRXLBP
WPRXLBN
WPRXSE1_IN
WPRXSE2_IN
PRX_QP
PRX_QN
DRX_QP
DRX_QN
TX_QP
TX_QN
GPIO_59
VCTCXO
19.2MHz
TX_ON
DAC_REF
GSM 900
RX SAW
DCS1800
RX SAW
GSM 850
RX SAW
PCS1900
RX SAW
I_IP_CH0
I_IM_CH0
Q_IP_CH0
Q_IM_CH0
I_IP_CH1
I_IM_CH1
Q_IP_CH1
Q_IM_CH1
I_OUT_P
I_OUT_N
Q_OUT_P
Q_OUT_N
Rx SAW
PDET_IN
W900
PAM
W900
DUPLEXER
W(1900)
DUPLEXER
W2100
DUPLEXER Coupler
Coupler
Coupler
W1900
PAM
WCDMA
TX SAW
WCDMA
TX SAW
WCDMA
TX SAW
LNA
GPIO_105TCXO_EN
VDDA
GPIO_106
SSBI TCXO
TCXO_OUT
TRK_LO_ADJ
TCXO_IN
BUFFER
Swift RF Block Diagram
W2100
PAM
MSM7227
Ant Sel 0,1,2,3
GPIO_72
GPIO_73
GPIO_74
GPIO_75
GPS_LNA_EN
GPIO_58
W2100
RX saw
WB_MX_INP
WB_MX_INM
WPRXSE2_OUT
USBPHY_SYSCLK
D-Flip
Flop
WCDMA_900_ON GPIO_22
WCDMA_1900_ON GPIO_110
WCDMA_2100_ON PA_ON0

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LGE Internal Use Only Copyright © 2010 LG Electronics. Inc. All right reserved.
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3. TECHNICAL BRIEF
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ͽ͸ͶͺΟΥΖΣΟΒΝΆΤΖ΀ΟΝΪ
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A generic, high-level functional block diagram of GT540 is shown in Figure 1-1. One antenna collects base station
forward link signals and radiates handset reverse link signals. The antenna connects with receive and transmit paths
through a ASM(Antenna-Switch-Module).
The UMTS receive paths each include an LNA, an RF band-pass filter, and a downconverter that translate the signal
directly from RF-to-baseband using radioOne ZIF techniques. The RFIC’s Rx analog baseband outputs, for the
receive chains, connect to the MSM IC. The UMTS and GSM Rx baseband outputs share the same inputs to the MSM
IC.
For the transmit chains, the RTR6285 IC directly translates the Tx baseband signals (from the MSM device) to an RF
signal using an internal LO generated by integrated onchip PLL and VCO. The RTR6285 IC outputs deliver fairly high-
level RF signals that are first filtered by Tx SAWs and then amplified by their respective UMTS PAs. In the GSM
receive path, the received RF signals are applied through their band-pass filters and down-converted directly to
baseband in the RTR6285 transceiver IC. These baseband outputs are shared with the UMTS receiver and routed to
the MSM IC for
further signal processing.
The GSM/EDGE transmit path employs one stage of up-conversion and, in order to improve efficiency, is divided
into phase and amplitude components to produce an open-loop Polar topology:
1. The on-chip quadrature up-converter translates the GMSK-modulated signal or 8-PSK modulated signal, to a
constant envelope phase signal at RF;
2. The amplitude-modulated (AM) component is applied to the ramping control pin of Polar power amplifier from a
DAC within the MSM GT540 power supply voltages are managed and regulated by the PM7540 Power Management
IC. This versatile device integrates all wireless handset power management, general housekeeping, and user
interface support functions into a single mixed signal IC.
It monitors and controls the external power source and coordinates battery recharging while maintaining the
handset supply voltages using low dropout, programmable regulators.
The device’s general housekeeping functions include an ADC and analog multiplexer circuit for monitoring on-chip
voltage sources, charging status, and current flow, as well as user-defined off-chip variables such as temperature, RF
output power, and battery ID.
Various oscillator, clock, and counter circuits support IC and higher-level handset functions. Key parameters such as
under-voltage lockout and crystal oscillator signal presence are monitored to protect against detrimental
conditions.

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Only for training and service purposes
LGE Internal Use Only
3. TECHNICAL BRIEF
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3.2 GSM MODE
3.2.1 GSM RECEIVER
The GSM-850, GSM-900, GSM-1800, and GSM-1900 receiver inputs of RTR6285 are connected directly to the
transceiver front-end Module. GSM-850, GSM-900, GSM-1800, and GSM-1900 receiver inputs use differential
configurations to improve common-mode rejection and second-order non-linearity performance. For example
Figure 1-2 shows receiver input topologies for DCS and PCS (GSM-850/900 have the same receiver input topologies).
The balance between the complementary signals is critical and must be maintained from the RF filter outputs all the
way into the IC pins.
[Figure 1-2] DCS and PCS Receiver Inputs Topologies
Since GSM-850, GSM-900, GSM-1800, and GSM-1900 signals are time-division duplex (the handset can only receive
or transmit at one time), switches are used to separate Rx and Tx signals in place of frequency duplexers – this is
accomplished in the switch module. The GSM-850, GSM-900, GSM-1800, and GSM-1900 receive signals are routed to
the RTR6285 through band selection filters and matching networks that transform single-ended 50-ΩGsources to
differential impedances optimized for gain and noise figure. The RTR input uses a differential configuration to
improve second-order intermodulation and common mode rejection performance. The RTR6285 input stages
include MSM-controlled gain adjustments that maximize receiver dynamic range.
The amplifier outputs drive the RF ports of the quadrature RF-to-baseband downconverters. The downconverted
baseband outputs are multiplexed and routed to lowpass filters (one I and one Q) having passband and stopband
characteristics suitable for GMSK or 8-PSK processing. These filter circuits include DC offset corrections. The filter
outputs are buffered and passed on to the MSM7227 IC for further processing asshown in Figure 1-4.