LG KS20 User manual

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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 RSSI 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 generation and distribution circuits ......25
3.5 Off-chip RF Components ...........................25
3.6 Digital Baseband(DBB/MSM7200) ............35
3.7 Hardware Architecture ...............................37
3.8. Subsystem(MSM7200) .............................39
3.9. Power Block..............................................42
3.10. External memory interface......................47
3.11. H/W Sub System ....................................49
3.12. Main Features.........................................76
4. TROUBLE SHOOTING.......................82
4.1 RF Component ..........................................82
4.2 SIGNAL PATH_UMTS RF .........................85
4.3 SIGNAL PATH_GSM RF ...........................86
4.4 Checking VCTCXO Block ..........................87
4.5 Checking Front-End Module Block ............89
4.6 Checking UMTS Block...............................91
4.7 Checking GSM Block.................................96
4.8 Checking Bluetooth Block........................102
4.9 Checking WLAN Block.............................104
4.10 Power ON Troubleshooting ...................108
4.11 Charger Troubleshooting .......................110
4.12 USB Troubleshooting.............................113
4.13 SIM Detect Troubleshooting ..................115
4.14 Camera Troubleshooting .......................117
4.15 Keypad Backlight Troubleshooting ........120
4.16 Main LCD Troubleshooting ....................121
4.17 Receiver Path ........................................122
4.18 Headset path .........................................124
4.19 Speaker phone path ..............................126
4.20 Main microphone ...................................128
4.21 Headset microphone..............................130
4.22 Vibrator ..................................................132
5. DOWNLOAD.....................................133
5.1 KS20 DOWNLOAD..................................133
6. BLOCK DIAGRAM ...........................146
6.1 GSM & UMTS RF Block ..........................146
6.2 Interface Diagram ....................................148
7. Circuit Diagram................................153
8. BGA IC PIN MAP..............................163
8. PCB LAYOUT ...................................169
9. Calibration & RF Auto Test
Program (Hot Kimchi) .....................177
9.1 Configuration of HOT KIMCHI .................177
9.2 How to use HOT KIMCHI.........................180
10. Phone Test Mode _ 3G smart
Phone KS20 ...................................182
11. EXPLODED VIEW & REPLACEMENT
PART LIST ..................................... 189
11.1 EXPLODED VIEW ................................ 189
11.2 Replacement Parts
<Mechanic component> ....................... 191
<Main component> ............................... 193
11.3 Accessory ............................................. 209
Table Of Contents
LGE Internal Use Only Copyright © 2007 LG Electronics. Inc. All right reserved.
Only for training and service purposes

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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
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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 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.
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 GSM900/1800/1900 and WCDMA2100 - Bar type Handset
Size 99.8 X 58 X 12.9 mm
Weight Under 92.5g (with 1050mAh Battery)
Power 3.7 V normal, 1050 mAh Li-Polymer
Talk Time Over 100 min (WCDMA, Tx=-23 dBm, Voice)
(with 800mAh) Over 150 min (GSM, Tx=Level 5, Voice)
Standby Time Over 300 Hrs (WCDMA, DRX=1.28)
(with 800mAh) Over 400 Hrs (GSM, Paging period=9)
Antenna Internal type
LCD Main 2.8” 262K 240 X 320 pixel (TFT)
LCD Backlight White LED Back Light
Camera Auto Focus - 2.0 Mega pixel (CMOS) + VGA Video Call Camera
Vibrator Yes (Coin Type)
LED Indicator Yes
MIC Yes
Receiver Yes
Earphone Jack Yes (18 pin)
Connectivity Bluetooth, USB
Volume Key Push Type(+, -)
External Memory Yes
I/O Connect 18 Pin

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2.2 Usable environment
1) Environment
2) Environment (Accessory)
* CLA : 12 ~ 24 V(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 3.7 V(Typ), 3.2 V(Min), [Shut Down : 3.2 V]
Operation Temp -20 ~ +60°C
Storage Temp -20 ~ +70°C
Humidity 85 % (Max)
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~[A]MHz -33dBm
Channel
1G~12.75GHz -33dBm
[A]M~[B]MHz -39dBm
Conducted [B]M~12.75GHz -33dBm
1Spurious 100k~880MHz -60dBm 100k~880MHz -60dBm
Emission 880M~915MHz -62dBm 880M~915MHz -62dBm
Idle Mode
915M~1GHz -60dBm 915M~1GHz -60dBm
1G~[A]MHz -50dBm 1G~[A]MHz -50dBm
[A]M~[B]MHz -56dBm [A]M~[B]MHz -56dBm
[B]M~12.5GHz -50dBm [B]M~12.5GHz -50dBm

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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~[A]MHz -30dBm
Channel
1G ~ 4GHz -30dBm
[A]M~[B]MHz -36dBm
Radiated [B]M~4GHz -30dBm
2Spurious 30M ~ 880MHz -57dBm 30M~880MHz -57dBm
Emission 880M ~ 915MHz -59dBm 880M~915MHz -59dBm
Idle Mode
915M~1GHz -57dBm 915M~1GHz -57dBm
1G~[A]MHz -47dBm 1G~[A]MHz -47dBm
[A]M~[B]MHz -53dBm [A]M~[B]MHz -53dBm
[B]M~4GHz -47dBm [B]M~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

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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

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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
-36dBm@f=9~150KHz, 1K BW
-36dBm@f=50KHz~30MHz, 10K BW
-36dBm@f=30MHz~1000MHz, 100K BW
14
Spurious Emissions -30dBm@f=1~12.5GHz, 1M BW
(*: additional requirement) (*)-41dBm@f=1893.5~1919.6MHz, 300K
(*)-67dBm@f=925~935MHz, 100K BW
(*)-79dBm@f=935~960MHz, 100K BW
(*)-71dBm@f=1805~1880MHz, 100K BW
15 Transmit Intermodulation
-31dBc@5MHz,Interferer -40dBc
-41dBc@10MHz, Interferer -40dBc
16 Error Vector Magnitude (EVM)
17.5%(>-20dBm)
(@12.2K, 1DPDCH+1DPCCH)
17 Transmit OFF Power
-15dB@SF=4.768Kbps, Multi-code
transmission
No Item GSM DCS & PCS
1 Sensitivity (TCH/FS Class II) -105dBm -105dBm
2
Co-Channel Rejection
C/Ic=7dB Storage -30 ~ +85
(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 1st Wanted Signal :-96dBm 1st
4 Intermodulation Rejection interferer:-44dBm 2nd interferer:-44dBm 2nd
interferer:-45dBm interferer:-44dBm
5
Blocking Response Wanted Signal :-101dBm Wanted Signal :-101dBm
(TCH/FS Class II, RBER) Unwanted : Depend on Frequency Unwanted : Depend on Frequency

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2. PERFORMANCE
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4) Receiver - WCDMA Mode
No Item Specification
1Reference Sensitivity Level -106.7 dBm(3.84 MHz)
-25dBm(3.84MHz)
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)
-44dBm/3.84MHz@f=2050~2095 and
2185~2230MHz
UE@+20dBm output power(Class3)
-30dBm/3.84MHz@f=2025~2050 and
5Out-band Blocking 2230~2255MHz
UE@+20dBm output power(Class3)
-15dBm/3.84MHz@f=1~2025 and
2255~12500MHz
UE@+20dBm output power(Class3)
6Spurious Response
-44dBm CW
UE@+20dBm output power(Class3)
-46dBm CW@10MHz
7Intermodulation Characteristic -46dBm/3.84MHz@20MHz
UE@+20dBm output power(Class3)
-57dBm@f=9KHz~1GHz, 100K BW
8Spurious Emissions -47dBm@f=1~12.5GHz, 1M BW
-60dBm@f=1920MHz~1980MHz, 3.84M BW
-60dBm@f=2110MHz~2170MHz, 3.84M BW

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2. PERFORMANCE
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2.4 Current Consumption
1) KS20 Current Consumption
(Stand by and Voice Call Test Condition : Bluetooth off, LCD backlight off,Neighbor Cell off) (VT Test
Condition : Speaker off, LCD backlight On)
2) KS20 Current Consumption
(Stand by and Voice Call Test Condition : Bluetooth off, LCD backlight off,Neighbor Cell off) (VT Test
Condition : Speaker off, LCD backlight On)
2.5 RSSI BAR
Stand by Voice Call VT
WCDMA
Under 4.00 mA Under 600 mA Under 800mA
(DRX=1.28) (Tx=23dBm) (Tx=23dBm)
Under 3.00 mA Under 350 mA
GSM Paging=9 period (PCL=5)
Level Change WCDMA GSM
BAR 4 → 3-82 ±2 dBm -91 ±2 dBm
BAR 3 → 2-92 ±2 dBm -96 ±2 dBm
BAR 2 → 1-102 ±2 dBm -101 ±2 dBm
BAR 1 → 0-112 ±2 dBm -106 ±2 dBm
Stand by Voice Call VT
WCDMA
Under 2.5 mA Under 330 mA Under 500mA
(DRX=2.56) (Tx=10dBm) (Tx=10dBm)
Under 2.7 mA Under 270 mA
GSM Paging=5 period (PCL=7)

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2.6 Battery BAR
2. PERFORMANCE
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Indication Standby
Bar 4 100% ~ 76%
Bar 4 →375%
Bar 3 →250%
Bar 2 →125%
Bar 1 →Empty 5%
Low Voltage, 10%
Warning message+ Blinking 5%
Power Off 3.20 ± 0.05V / 0%

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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 : 900 mA
• Normal Battery Capacity : 1050 mAh
• Charging Time : Max 2.5 hours (except for trickle charging time)
• Full charging indication current (charging icon stop current) : 60 mA
• Cut-off voltage : 3.20 V
No Test Item Specification
1Sending Loudness Rating (SLR) 8 ±3 dB
2Receiving Loudness Rating (RLR) Nor 2 ± 3 dB
Max -13 dB
3Side Tone Masking Rating (STMR) Min 23 dB
4Echo Loss (EL) Min 46 dB
5Idle Noise-Sending (INS) Max -64 dBm0p
6Idle Noise-Receiving (INR) Nor Under -54 dBPA
Max
7Sending Loudness Rating (SLR) 8±3dB
8Receiving Loudness Rating (RLR) Nor -1 ±3 dB
Max -12 ±3 dB
9Side Tone Masking Rating (STMR) Min 25 dB
10 Echo Loss (EL) Min 40 dB
11 Idle Noise-Sending (INS) Max -55 dBm0p
12 Idle Noise-Receiving (INR) Nor Under -45 dBPA
Max Under -40 dBPA
TDMA Noise
-. GSM : Power Level : 5
DCS/PCS : Power Level : 0
(Cell Power : -90 ~ -105 dBm)
13
-. Acoustic (Max Vol.)
MS/Headset SLR : 8 ± 3dB
MS/Headset RLR : -15 ± 3dB/-12 dB
(SLR/RLR : Mid-value setting)
MS
Headset
MS and
Headset
Max Under -62 dBm

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3. TECHNICAL BRIEF
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3.1 General Description
The KS20 supports UMTS-2100, GSM-900, DCS-1800, and PCS-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.
1QUALCOMM’s branded chipset that implements a Zero-IF radio architecture.
3. TECHNICAL BRIEF
[Fig 1.1] Block diagram of RF part

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A generic, high-level functional block diagram of KS20 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).
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 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 bandpass 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 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
KS20 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.
3. TECHNICAL BRIEF
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3. TECHNICAL BRIEF
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3.2 GSM Mode
3.2.1 GSM Receiver
The Dual-mode KS20’s receiver functions are split between the three RFICs as follows:
• GSM-900, DCS-1800, and PCS-1900 UMTS-2100 modes bot 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, antenna switch module(LSHS-M090U) which includes 3 RX saw
filters(GSM900, DCS and PCS). The antenna switch module allows multiple operating bands and
modes to share the same antenna. In KS20, a common antenna connects to one of six paths: 1)
UMTS-2100 Rx/Tx, 2) GSM-900 Rx, 3) GSM-900 Tx, 4) DCS-1800 Rx, and 5) DCS-1800, PCS-1900
Tx(High Band Tx’s share the same path), 6) PCS-1900 Rx. 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.
ANT_SEL0 ANT_SEL1 ANT_SEL2
GSM 850/GSM 900 TX HIGH HIGH LOW
GSM 1800/GSM 1900 TX HIGH LOW LOW
GSM 850 RX - - -
GSM 900 RX LOW LOW LOW
GSM 1800 RX LOW LOW LOW
GSM 1900 RX LOW LOW HIGH
WCDMA HIGH LOW HIGH
[Table 1.1] Antenna Switch Module Control logic

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The GSM900, DCS, and PCS receiver inputs of RTR6275 are connected directly to the transceiver
front-end circuits(filters and antenna switch module). GSM900, DCS, and PCS receiver inputs 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 switch module.
The GSM900, DCS, and PCS receive signals are routed to the RTR6275 through band selection filters
and matching networks that transform single-ended 50-Ω sources to differential impedances optimized
for gain and noise figure. The RTR input uses a differential configuration to improve second-order inter-
modulation and common mode rejection performance. The RTR6275 input stages include
MSMcontrolled 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 MSM7200 IC
for further processing (an interface shared with the RFR6275 UMTS receiver outputs
3. TECHNICAL BRIEF
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3. TECHNICAL BRIEF
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[Fig 1.2] RTR6275 RX feature

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Only for training and service purposes
3.2.2 GSM Transmitter
The RTR6275 transmitter outputs(DA_HB2_OUT and DA_LB1_OUT)include on-chip output matching
inductors. 50ohm output impedance is achieved by adding a series capacitor at the output pins. The
capacitor value may be optimized for specific applictions and PCB characteristics based on pass-band
symmetry about the band center frequency, the suggested starting value is shown in Figure1.2.
The RTR6275 IC is able to support GSM 900 and GSM 1800/1900 mode transmitting. This design
guideline shows a tri-band GSM application.
Both high-band and low band outputs are followed by resistive pads to ensure that the load Presented
to the outputs remains close to 50ohm. The low-band GSM. Tx path also includes a Tx-band SAW filter
to remove noise-spurious components and noise that would be amplified by the PA and appear in the
GSM Rx band
3. TECHNICAL BRIEF
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300Ω300Ω
300Ω300Ω
18Ω
18Ω
[Fig 1.3] GSM Transmitter matching