LG L704I User manual

Date: September, 2007 / Issue 1.0
Service Manual Model : L704i
Service Manual
L704i
Internal Use Only

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1. INTRODUCTION .............................. 5
1.1 Purpose................................................... 5
1.2 Regulatory Information............................ 5
2. PERFORMANCE...............................7
2.1 System Overview .....................................7
2.2 Usable environment .................................8
2.3 Radio Performance ..................................8
2.4 Current Consumption.............................14
2.5 Antenna BAR .........................................14
2.6 Battery BAR ...........................................15
2.7 Sound Pressure Level............................16
2.8 Charging ................................................16
3. TECHNICAL BRIEF ........................17
3.1 General Description ...............................17
3.2 GSM Mode.............................................19
3.3 UMTS Mode...........................................23
3.4 LO Phase-locked Loop ..........................26
3.5 Off-chip RF Components .......................28
3.6 Digital Baseband(DBB/MSM6280).........36
3.7 Block Diagram(MSM6280).....................38
3.8. Subsystem(MSM6280) .........................39
3.9. Power Block ..........................................46
3.10. External memory interface ..................51
3.11 H/W Sub System..................................52
3.12 Main Features ......................................71
4. TROUBLE SHOOTING ...................77
4.1 RF Component.......................................77
4.2. Checking VCXO Block ..........................80
4.3. Checking Ant. SW Module Block ..........82
4.4. Checking UMTS Block ..........................85
4.5. Checking GSM Block ............................94
4.6. Power ON Troubleshooting...................97
4.7. Charger Troubleshooting ....................100
4.8. USB Troubleshooting..........................103
4.9 SIM Detect Troubleshooting ................105
4.10 Keypad Backlight Troubleshooting ....111
4.11 Slide Close / Open Troubleshooting ..112
4.12 Main LCD Troubleshooting ................113
4.13 Receiver Path ....................................114
4.14 Headset path......................................116
4.15 Speaker phone path...........................118
4.16 Main microphone ...............................120
4.17 Headset microphone..........................122
4.18 Vibrator ..............................................124
5. DOWNLOAD .................................125
5.1 Introduction ..........................................125
5.2 Downloading Procedure.......................125
5.3 Troubleshooting Download Errors .......139
5.4 Caution.................................................143
6. BLOCK DIAGRAM ........................146
6.1 GSM & UMTS RF Block.......................146
6.2 Interface Diagram ................................148
7. Circuit Diagram ............................153
8. BGM Pin Map................................163
9. PCB LAYOUT................................165
10. Calibration & RF Auto Test
Program (Hot Kimchi)................173
10.1 Configuration of HOT KIMCHI ...........173
10.2 How to use HOT KIMCHI...................174
11. EXPLODED VIEW &
REPLACEMENT PART LIST ..... 177
11.1 EXPLODED VIEW ............................ 177
11.2 Replacement Parts
<Mechanic component>.................... 179
<Main component> ........................... 182
11.3 Accessory ......................................... 202
Table Of Contents
LGE Internal Use Only Copyright © 2007 LG Electronics. Inc. All right reserved.
Only for training and service purposes

- 4 -
LGE Internal Use Only Copyright © 2007 LG Electronics. Inc. All right reserved.
Only for training and service purposes

LGE Internal Use Only Copyright © 2007 LG Electronics. Inc. All right reserved.
Only for training and service purposes
- 5 -
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 commoncarrier
telecommunication service of facilities accessed through or connected to it. The manufacturer will not
be responsible for any charges that resultfrom 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.
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.
1. INTRODUCTION
1. INTRODUCTION

LGE Internal Use Only Copyright © 2007 LG Electronics. Inc. All right reserved.
Only for training and service purposes
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.
1. INTRODUCTION
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LGE Internal Use Only Copyright © 2007 LG Electronics. Inc. All right reserved.
Only for training and service purposes
2. PERFORMANCE
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2.1 System Overview
2. PERFORMANCE
Item Specification
Shape WCDMA2100,800/GSM900/DCS1800/PCS1900 Slider , Dual mode
Size 99X48X17.7 [mmXmmXmm]
Weight 110g (with 1000mAh Battery)
Power 3.7V, 1000mAh Li-Polymer
Talk Time Over 150 min. (WCDMA, Tx=10 dBm, Voice call) 350 mA
(with 1000mAh) Over 150 min (GSM900, Tx=29 dBm, Voice call) 350 mA
Standby Time Over 400 hrs (WCDMA only mode, DRX = 2.56s) (under 2.5mA)
(with 1000mAh) Over 300 hrs (GSM, Paging period = 5) (under 3.0 mA)
Charging duration About 2 hours 40 min ( 0° ~ 40° )
Antenna Intenna
Main LCD 320X240, 2.2”, TFT
Main LCD BL White LED Back Light
Vibrator Yes (10 pie coin type)
LED Indicator Yes
C-Mic Yes (SMD type)
Receiver Yes (9X6)
Loud Speaker Yes (16 pie uni-direction)
Ear phone jack Yes (10 pin)
SIM Socket Yes (3.0V/1.8V)
Volume Key Push Type Side Key(+,-)
Voice Key Push Type
I/O Connector ARIB Type A (10 pin + RF coaxial)

LGE Internal Use Only Copyright © 2007 LG Electronics. Inc. All right reserved.
Only for training and service purposes
2.2 Usable environment
1) Environment
2) Environment (Accessory)
* CLA : 12~24V (DC)
2.3 Radio Performance
1) Transmitter-GSM Mode
* In case of DCS : [A] -> 1710, [B] -> 1785 * In case of PCS : [A] -> 1850, [B] -> 1910
2. PERFORMANCE
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Item Specification
Voltage 3.7V (Typ) ( Shut Down: 3.28V)
Operation Temp -20 ~ +60°C
Storage Temp -30 ~ +85°C
Humidity 40% ~ 85%
Reference Spec. Min Typ. Max Unit
TA Power Available power 100 220 240 Vac
No Item GSM DCS & PCS
100k~1GHz -39dBm
9k ~ 1GHz -39dBm
MS allocated 1G ~ 1710MHz -33dBm
Channel
1G~12.75GHz -33dBm
1710M ~ 1785MHz -39dBm
Conducted 1785M ~ 12.75GHz -33dBm
1Spurious 100k ~ 880MHz -60dBm 100k ~ 880MHz -60dBm
Emission 880M ~ 915MHz -62dBm 880M ~ 915MHz -62dBm
Idle Mode
915M ~ 1000Mz -60dBm 915M ~ 1000MHz -60dBm
1G ~ 1.71GHz -50dBm 1G ~ 1.71GHz -50dBm
1.71G ~ 1.785GHz -56dBm 1.71G ~ 1.785GHz -56dBm
1.785G ~ 12.75GHz -50dBm 1.785G ~ 12.75GHz -50dBm

LGE Internal Use Only Copyright © 2007 LG Electronics. Inc. All right reserved.
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2. PERFORMANCE
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* In case of DCS : [A] -> 1710, [B] -> 1785 * In case of PCS : [A] -> 1850, [B] -> 1910
No Item GSM DCS & PCS
30M ~ 1GHz -36dBm
30M ~ 1GHz -36dBm
MS allocated 1G ~ 1710MHz -30dBm
Channel
1G ~ 4GHz -30dBm
1710M ~ 1785MHz -36dBm
Radiated 1785M ~ 4GHz -30dBm
2Spurious 30M ~ 880MHz -57dBm 30M ~ 880MHz -57dBm
Emission 880M ~ 915MHz -59dBm 880M ~ 915MHz -59dBm
Idle Mode
915M ~ 1000MHz -57dBm 915M ~ 1000MHz -57dBm
1G ~ 1.71GHz -47dBm 1G ~ 1.71GHz -47dBm
1.71G ~ 1.785GHz -53dBm 1.71G ~ 1.785GHz -53dBm
1.785G~ 4GHz -47dBm 1.785G~ 4GHz -47dBm
3Frequency Error ±0.1ppm ±0.1ppm
4Phase Error
±5(RMS) ±5(RMS)
±20(PEAK) ±20(PEAK)
3dB below reference sensitivity 3dB below reference sensitivity
Frequency Error RA250 : ±200Hz RA250: ±250Hz
5Under Multipath and HT100 : ±100Hz HT100: ±250Hz
Interference Condition TU50 : ±100Hz TU50: ±150Hz
TU3 : ±150Hz TU1.5: ±200Hz
0 ~ 100kHz +0.5dB 0 ~ 100kHz +0.5dB
200kHz -30dB 200kHz -30dB
250kHz -33dB 250kHz -33dB
Due to 400kHz -60dB 400kHz -60dB
Output RF
modulation 600 ~ 1800kHz -66dB 600 ~ 1800kHz -60dB
61800 ~ 3000kHz -69dB 1800 ~ 6000kHz -65dB
Spectrum
3000 ~ 6000kHz -71dB ≥6000kHz -73dB
≥6000kHz -77dB
Due to
400kHz -19dB 400kHz -22dB
Switching
600kHz -21dB 600kHz -24dB
transient
1200kHz -21dB 1200kHz -24dB
1800kHz -24dB 1800kHz -27dB

LGE Internal Use Only Copyright © 2007 LG Electronics. Inc. All right reserved.
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2. PERFORMANCE
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No Item GSM DCS & PCS
Frequency offset 800kHz
7Intermodulation attenuation –
Intermodulation product should
be Less than 55dB below the
level of Wanted signal
Power control Power Tolerance Power control Power Tolerance
Level (dBm) (dB) Level (dBm) (dB)
533±3 030±3
631±3 128±3
729±3 226±3
827±3 324±3
925±3 422±3
10 23 ±3 5 20 ±3
8Transmitter Output Power 11 21 ±3 6 18 ±3
12 19 ±3 7 16 ±3
13 17 ±3 8 14 ±3
14 15 ±3 9 12 ±4
15 13 ±3 10 10 ±4
16 11 ±5 11 8 ±4
17 9 ±5 12 6 ±4
18 7 ±5 13 4 ±4
19 5 ±5 14 2 ±5
15 0 ±5
9Burst timing Mask IN Mask IN

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2. PERFORMANCE
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2) Transmitter - WCDMA Mode
No Item Specification
1Maximum Output Power Class 3 : +24dBm(+1/-3dB)
2Frequency Error ±0.1ppm
3Open Loop Power control in uplink ±9dB@normal, ±12dB@extreme
Adjust output(TPC command)
cmd 1dB 2dB 3dB
+1 +0.5/1.5 +1/3 +1.5/4.5
4Inner Loop Power control in uplink 0 -0.5/+0.5 -0.5/+0.5 -0.5/+0.5
-1 -0.5/-1.5 -1/-3 -1.5/-4.5
Group (10 equel command group)
+1 +8/+12 +16/+24
5Minimum Output Power -50dBm(3.84MHz)
Qin/Qout : PCCH quality levels
6Out-of-synchronization handling of output power Toff@DPCCH/Ior : -22 -> -28dB
Ton@DPCCH/Ior : -24 -> -18dB
7Transmit OFF Power -56dBm(3.84MHz)
8Transmit ON/OFF Time Mask
±25us
PRACH,CPCH,uplinlk compressed mode
±25us
9Change of TFC
Power varies according to the data rate
DTX : DPCH off
(minimize interference between UE)
10 Power setting in uplink compressed ±3dB(after 14slots transmission gap)
11 Occupied Bandwidth(OBW) 5MHz(99%)
-35-15*(∆f-2.5)dBc@∆f=2.5~3.5MHz,30k
12 Spectrum emission Mask
-35-1*(∆f-3.5)dBc@∆f=3.5~7.5MHz,1M
-39-10*(∆f-7.5)dBc@∆f=7.5~8.5MHz,1M
-49dBc@∆f=8.5~12.5MHz,1M

LGE Internal Use Only Copyright © 2007 LG Electronics. Inc. All right reserved.
Only for training and service purposes
3)Receiver - GSM Mode
2. PERFORMANCE
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No Item Specification
13 Adjacent Channel Leakage Ratio(ACLR)
33dB@5MHz, ACP>-50dBm
43dB@10MHz, ACP>-50dBm
-36 dBm @f=9~150KHz, 1k BW
WCDMA -36 dBm @f=150KHz~30MHz, 10k
2100, 800 -36 dBm @f=30~1000MHz, 100k
14
Spurious Emissions -30 dBm @f=1~12.75GHz, 1M
(*: additional requirement) -41 dBm* @1893.5~1919.6MHz, 300k
WCDMA -67 dBm* @925~935MHz, 100k
2100 -79 dBm* @935~960MHz, 100k
-71 dBm* @1805~1880MHz, 100k
-60 dBm* @869~894MHz, 3.84M
WCDMA -60 dBm* @1930~1990MHz, 3.84M
800 -60 dBm* @2110~2155MHz, 3.84M
15 Transmit Intermodulation
-31 dBc @5MHz,Interferer -40dBc
-41 dBc @10MHz,Interferer -40dBc
16 Error Vector Magnitude (EVM)
17.5 % ( >-20dBm)
(@12.2k, 1DPDCH+1DPCCH)
17 Transmit OFF Power
-15 dB@SF=4, 768kbps, multi-code
transmission
No Item GSM DCS & PCS
1 Sensitivity (TCH/FS Class II) -102dBm -102dBm
2
Co-Channel Rejection
C/Ic= 7dB C/Ic= 7dB
(TCH/FS Class II, RBER, TU high/FH)
3Adjacent Channel 200kHz C/Ia1=-12dB C/Ia1=-12dB
Rejection 400kHz C/Ia2=-44dB C/Ia2=-44dB
Wanted Signal :-98dBm Wanted Signal :-96dBm
4 Intermodulation Rejection 1st interferer:-44dBm 1st interferer:-44dBm
2nd interferer:-45dBm 2nd interferer:-44dBm
5
Blocking Response Wanted Signal :-101dBm Wanted Signal :-101dBm
(TCH/FS Class II, RBER) Unwanted : Depend on Frequency Unwanted : Depend on Frequency

LGE Internal Use Only Copyright © 2007 LG Electronics. Inc. All right reserved.
Only for training and service purposes
2. PERFORMANCE
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4) Receiver - WCDMA Mode
No Item Specification
1Reference Sensitivity Level -106.7dBm(3.84M)
-25 dBm(3.84 MHz)
2Maximum Input Level -44dBm/3.84MHz(DPCH_Ec)
UE@+20dBm output power(Class3)
3Adjacent Channel Selectivity (ACS)
33dB
UE@+20dBm output power(Class3)
-56dBm/3.84MHz@10MHz
4In-band Blocking UE@+20dBm output power(Class3)
-44dBm/3.84MHz@15MHz
UE@+20dBm output power(Class3)
-44 dBm/3.84MHz @f=2050~2095 &
2185~2230 MHz , band a)
UE@ =20dBm output power(class3)
-30 dBm/3.84MHz @f=2025~2050 &
5Out-band Blocking 2230~2255 MHz, band a)
UE@ +20dBm output power(class3)
-15 dBm/3.84MHz @f=1~2025 &
2255~12500 MHz, band a)
UE@ +20dBm output power(class3)
6Spurious Response
-44dBm CW
UE@ +20dBm output power(class3)
-46 dBm CW@10MHz &
7Intermodulation Characteristic -46dBm/3.84MHz @20MHz
UE@ +20dBm output power(class3)
WCDMA -57 dBm @f=9KHz~1GHz, 100k BW
2100, 800 -47 dBm @f=1~12.75GHz, 1M
8Spurious Emissions WCDMA -60 dBm @f=1920~1980MHz, 3.84MHz
2100 -60 dBm @f=2110~2170MHz, 3.84MHz
WCDMA -60 dBm @f=824~849MHz, 3.84MHz
800 -60 dBm @f=869~894MHz, 3.84MHz

LGE Internal Use Only Copyright © 2007 LG Electronics. Inc. All right reserved.
Only for training and service purposes
2. PERFORMANCE
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2.4 Current Consumption
Stand by and Voice Call Test condition: LCD backlight Off
VT Test condition: Speaker off, LCD backlight off
2.5 Antenna BAR
Antenna Bar WCDMA GSM
BAR 3 RSCP>= -105 dBm RSSI >= -95dBm
and Ec/Io >= -12 dBm
BAR 2 (RSCP< -105dBm or Ec/Io< -12dBm ) and -100 <= RSSI < -95dBm
(Ec/Io >= -14 dBm and RSCP >=-110 dBm)
BAR 1 (RSCP< -110 dBm or Ec/Io< -14dBm ) and -105 <= RSSI < -100dBm
(Ec/Io >= -17 dBm and RSCP >=-113 dBm)
Network Notification RSSI < -105dBm
Stand by Voice Call VT
WCDMA
400 Hours (2.5mA) 150 Min (350mA) 90 Min (650mA)
(DRX=2.56) (Tx=10dBm) (Tx=10dBm)
300 Hours (3.0mA) 150 Min (350mA)
GSM (Paging period = 5) (Tx=Max)

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2.6 Battery BAR
2. PERFORMANCE
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Indication Voltage
During Idle state During Call state
BAR 3 -> 2 3.75 ± 0.05V 3.64 ± 0.05V
(call maintenance over 40min)
BAR 2 -> 1 3.63 ± 0.05V 3.53 ± 0.05V
(call maintenance over 10min)
BAR 1 -> 0 [Idle & Talk] 3.30V ± 0.05V [Idle & Talk] 3.30V ± 0.05V
(Icon Blinking) [Under -10deg] 3.00V ± 0.05V [Under -10deg] 3.00V ± 0.05V
Low battery message BAR 1 -> 0
Low battery pop-up BAR 2 -> 1, display one time
Power OFF during call - 80s after Low battery message
Power OFF at stand-by 60s after Low battery message -

LGE Internal Use Only Copyright © 2007 LG Electronics. Inc. All right reserved.
Only for training and service purposes
2. PERFORMANCE
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2.7 Sound Pressure Level
2.8 Charging
• Charging Method : CC & CV (Constant Current and Constant Voltage)
• Maximum Charging Voltage : 4.2 V
• Maximum Charging Current : 600 mA
• Normal Battery Capacity : 1000 mAh
• Charging Time : Max 160 min (except for trickle charging time)
• Full charging indication current (charging icon stop current) : 140 mA
• Cut-off voltage : 3.3 V
-40dBPAMAX
-45dBPANOM
Idle Noise-Receiving (INR)
14
MAX
-55dBm0p
NOM
Idle Noise-Sending (INS)
13
MAX
40dB
NOM
Echo Loss (EL)
12
MAX
25dB
NOM
Side Tone Masking Rating
(STMR)
11
-12 3dBMAX
-1 3dBNOM
Receiving Loudness Rating
(RLR)
10
MAX
83dB
NOM
Head
set
Sending Loudness Rating
(SLR)
9
A
C
O
U
S
T
I
C
A
I
R
-36dBPAMAX
-47dBPANOM
Idle Noise-Receiving (INR)
8
MAX
-64dBm0p
NOM
Idle Noise-Sending (INS)
7
MAX
40dB
NOM
Echo Loss (EL)
6
MAX
17dB
NOM
Side Tone Masking Rating
(STMR)
5
MASK INMAX
Receiving Frequency
Response (RFR)
4
-15 3dBMAX
-4 3dBNOM
Receiving Loudness Rating
(RLR)
3
MASK INMAX
Sending Frequency
Response (SFR)
2
MAX
83dB
NOM
M/S
Sending Loudness Rating
(SLR)
1
A
C
O
U
S
T
I
C
A
I
R
SpecificationTest ItemNO
↑
↑
↑
↑
↓
↓
↓
↓
↓
↓
±
±
±
±
±
±

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3. TECHNICAL BRIEF
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3.1 General Description
The L704i supports UMTS-800, UMTS-2100, GSM-900, DCS-1800, and PCS-1900 based
GSM/GPRS/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.
A generic, high-level functional block diagram of L704i 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 FEM(Front End Module) (plus two duplexers for UMTS high-band
and low-band operations).
1QUALCOMM’s branded chipset that implements a Zero-IF radio architecture.
3. TECHNICAL BRIEF
Fig 1.1 Block diagram of RF part

LGE Internal Use Only Copyright © 2007 LG Electronics. Inc. All right reserved.
Only for training and service purposes
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 (at ADC1).
For the transmit chains, the RTR6275 IC directly translates the Tx baseband signals (from the MSM
device) to an RF signal using an internal LO generated by integrated on-chip PLL and VCO. The
RTR6275 IC outputs deliver fairly high-level RF signals that are first filtered by Tx SAWs and then
amplified by their respective UMTS PAs. The high- and low-band UMTS RF transmit signals emerge
from the RTR6275 transceiver.
In the GSM receive path, the received RF signals are applied through their band-pass filters and
down-converted directly to baseband in the RTR6275 transceiver IC. These baseband outputs are
shared with the UMTS receiver and routed to the MSM IC for further signal processing. The RFR6275
GSM/UMTS IC receiver baseband outputs share the same interface to the MSM IC input ADC as the
RTR6275 IC baseband outputs.
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
L704i power supply voltages are managed and regulated by the PM6650 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 userdefined 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
3. TECHNICAL BRIEF
- 18 -

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3. TECHNICAL BRIEF
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3.2 GSM Mode
3.2.1 GSM Receiver
The Dual-mode L704i’s receiver functions are split between the three RFICs as follows:
• UMTS-800 operation uses the RFR6275 Receiver ICs to implement the receive signal path,
accepting an RF input and delivering analog baseband outputs (I and Q).
• GSM-900, DCS-1800, and PCS-1900 modes both use the RTR6275 IC only. Each mode has
independent front-end circuits and down-converters, but they share common baseband circuits (with
only one mode active at a time). All receiver control functions are beginning with SBI2-controlled
parameters.
RF Front end consists of antenna, front end module (LMSP54MA-543) which includes three RX saw
filters(GSM900, DCS and PCS). The front end module allows multiple operating bands and modes to
share the same antenna. In L704i, a common antenna connects to one of seven paths: 1) UMTS-800
Rx/Tx, 2) UMTS-2100 Rx/Tx, 3) GSM-900 Rx, 4) DCS-1800 Rx, 5) PCS-1900 Rx , 6) GSM-900 Tx, 7)
DCS-1800 PCS-1900 Tx.
UMTS operation requires simultaneous reception and transmission, so the UMTS Rx/Tx connection is
routed to a duplexer that separates receive and transmit signals. GSM900, DCS, and PCS operation is
time division duplexed, so only the receiver or transmitter is active at any time and a frequency
duplexer is not required.
2The RFIC operating modes and circuit parameters are MSM-controlled through the proprietary 3-line Serial Bus Interface (SBI). The Application
Programming Interface (API) is used to implement SBI commands. The API is documented in AMSS Software - please see applicable AMSS
Software documentation for details.
CTRL1 CTRL2 CTRL3
EGSM TX HIGH HIGH LOW
DCS/PCS TX HIGH LOW LOW
EGSM RX LOW LOW HIGH
DCS RX LOW HIGH HIGH
PCS RX LOW HIGH LOW
UMTS 1 HIGH LOW HIGH
UMTS 2 HIGH HIGH HIGH
FRONT END MODULE LOGIC
Table 1.1 Front End Module Control logic

LGE Internal Use Only Copyright © 2007 LG Electronics. Inc. All right reserved.
Only for training and service purposes
The GSM900, DCS, and PCS receiver inputs of RTR6275 are connected directly to the transceiver
front-end circuits(filters and front end module). GSM900, DCS, and PCS receiver inputs are similar to
the RFR6275 UMTS Rx input in that they also use differential configurations to improve common-mode
rejection and second-order non-linearity performance. The balance between the complementary signals
is critical and must be maintained from the RF filter outputs all the way into the IC pins.
Since GSM900, DCS, and PCS 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 front end module.
The GSM900, DCS, and PCS receive signals are routed to the RTR6275 through band selection filters
and matching networks that transform single-ended 50Ωsources to differential impedances optimized
for gain and noise figure. Similar to the RFR, the RTR input uses a differential configuration to improve
second-order inter-modulation and common mode rejection performance. The RTR6275 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 MSM6280
IC for further processing (an interface shared with the RFR6275 UMTS receiver outputs
3. TECHNICAL BRIEF
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LGE Internal Use Only Copyright © 2007 LG Electronics. Inc. All right reserved.
Only for training and service purposes
3. TECHNICAL BRIEF
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RTR6275 RX feature