Samsung SCH-570 Service Manual

CDMA Portable
Cellular Telephone

SCH-570

SERVICE

Manual

CDMA Portable Cellular Telephone

CONTENTS

1. General Intro d u c t i o n

2. Specification

3. NAM Pro g r a m m i n g

4. Data Tr a n s f e r

5. Circuit Description

6. Exploded View and Its Parts List

7. PCB Diagrams

8. Tro u b l e s h o o t i n g

9. Test Command Ta b l e

10. Block & Circuit Diagrams

Samsung Electronics Co.,Ltd. SEP. 1998.
Printed in Korea
Code No. : GH68-60724A

HONGKONG CHINA.

1. General Introduction

The SCH-570 cellular phone functions as only digital cellular phone working in CDMA (Code Division
Multiple Access) mode. CDMA type digital mode applies DSSS (Direct Sequential Spread spectrum) mode
which first came to be used in the military.
The DSSS reduces channel cross talk and allow to use one frequency channel by multiple users in the same
specific area, resulting in increase of channel capacity to about ten times compared to that of analog mode
currently used.

Soft/Softer Handoff, Hard Handoff, and Dynamic RF Power Control technologies are combined into this
phone to reduce the call drop while usage.

CDMA digital cellular network consists of MSO (Mobile Switching Office), BSC (Base Station Controller),
BTS (Base Station Transmission System), and MS (Mobile Station). MS meets the specifications of the below:

IS-95A : Mobile Station-Base Station Compatibility Standard for Dual-Mode Wideband Spread Spectrum
Cellular System

IS-96A : Speech Service Option 1 Standard for Dual-Mode Wideband Spread Spectrum Cellular Systems
IS-98A : Standards for Dual-Mode Wideband Spread Spectrum Cellular Mobile Station
IS-126 : Mobile Station Loopback Service Options Standard

SCH-570 is composed of main handset, desktop charger, standard battery.

1.1 General

Frequency Range

Transmitter : 824.64 ~ 848.37 MHz

Receiver : 869.64 ~ 893.37 MHz
Channel Spacing : 1.23 MHz
Number of Channels : 20 FA
Duplex Spacing : 45 MHz

MSC Transmitter Frequency

FA NO. CH. NO. CENTER FREQUENCY FA NO. CH. NO. CENTER FREQUENCY

1 1011 824.640MHz 11 404 837.120MHz
2 29 825.870MHz 12 445 838.350MHz
3 70 827.100MHz 13 486 839.580MHz
4 111 828.330MHz 14 527 840.810MHz
5 152 829.560MHz 15 568 842.040MHz
6 193 830.790MHz 16 609 843.270MHz
7 234 832.020MHz 17 650 844.270MHz
8 275 833.250MHz 18 697 845.910MHz
9 316 834.480MHz 19 738 847.140MHz

10 363 835.890MHz 20 779 848.370MHz

MSC Receiver Frequency

FA NO. CH. NO. CENTER FREQUENCY FA NO. CH. NO. CENTER FREQUENCY

1 1011 869.640MHz 11 404 882.120MHz
2 29 870.870MHz 12 445 883.350MHz
3 70 872.100MHz 13 486 884.580MHz
4 111 873.330MHz 14 527 885.810MHz
5 152 874.560MHz 15 568 887.040MHz
6 193 875.790MHz 16 609 888.270MHz
7 234 877.020MHz 17 650 889.270MHz
8 275 878.250MHz 18 697 890.910MHz
9 316 879.480MHz 19 738 892.140MHz

10 363 880.890MHz 20 779 893.370MHz

2. Specification

2-1

Frequency Range Transmitter : 824.64 MHz ~ 848.37MHz
Frequency Range Receiver : 869.64 MHz ~ 893.37 MHz
Waveform Quality : above 0.944

Time Reference : within 1uS
RX Sensitivity : 104 dBm, FER = within 0.5%

Dynamic Range : 104 dBm ~ 25 dBm, FER = within 0.5%
TX Output Power : Maximum 320 mW (25dBm)
TX Frequency Deviation : within 300 Hz
Occupied Band Width : 1.32 MHz
TX Conducted Spurious Emissions : 900 kHz below 42 dBc / 30 kHz

: 1.98 MHz below 54 dBc / 30 kHz
Minimum TX Power Control : below 50 dBm
Open Loop Power Control : 25 dBm : 57.0 dBm ~ 38.5 dBm

65 dBm : 17.5 dBm ~ 1.5 dBm
104 dBm : 18.0 dBm ~ 30.0 dBm

Stand-by Output Power : below 61 dBm

Closed Loop TX Power Control Range : Test 1 within 24 dB

Test 2 0 ms ~ 2.5 ms
Test 3 within 24 dB
Test 4 within 24 dB

Test 5 within 24 dB

Size (mm) : 108 46 25 (Standard battery)
Weight (g) : 128 (1000mA Standard battery)

5. Circuit Description

5-1 Logic Section

5-1-1 Power Supply

With the battery installed on the phone and by
pressing the END/ key, the VBATT and
ON_SW signals will be connected. This will turn
on U123 DC_DC convertor.
This in turn will be supplied to PIN3, PIN4 of
regulators U124, PIN6 of regulators U122, thus
releasing them from the shut-down state to output
regulated 3.3V. ( The VBATT applied to ON-SW
will turn on Q103(DTC144EE) resulting in the
signal ON_SW_SENSE to change the start from
High to Low.)
The MSM recognizes this signal and sends out
PS_HOLD (logical HIGH) to turn on Q102 even
after the PWR key is released.
The power from U124 is used in the digital part of
MSM and BBA. The power from U122 is used in
analog part of BBA.

5-1-2 Logic Part

The logic part consists of internal CPU of MSM,
RAM, ROM and EEPROM. The MSM receives
TCXO and CHIPX8 clock signals from the BBA
and controls the phone during the operation. The
major components are as follows:

CPU : INTEL 80186 core (inside the MSM)
FLASH ROM : U701 - 8 Mbit FLASH MEMORY
SRAM : U703 - 2 Mbit STATIC RAM
FLASH ROM : U702 - 1 Mbit FLASH MEMORY
EEPROM : U102 - 128 Kbit SERIAL EEPROM

CPU

INTEL 80186 CMOS type 16-bit microprocessor is
used for the main processing. The CPU controls all
the circuitry. For the CPU clock, 27MHz resonator
is used.

FLASH ROM

One 8 MBIT FROM is used to store the terminal's
program. Using the down-loading program, the
program can be changed even after the terminal is
fully assembled.

SRAM

One 2 MBIT SRAM is used to store the internal
flag information, call processing data, and timer
data.

EEPROM

One 128 KBIT EEPROM is used to store ESN,
NAM, power level, volume level, and telephone
number.

KEYPAD

For key recognition, key matrix is to set up using
SCAN0-6 of STORE signals and KEY0-3 of input
ports of MSM. Ten LEDs and backlighting
circuitry are included in the keypad for easy
operation in the dark.

LCD MODULE

LCD module contains a controller which will
display the information onto the LCD by 8-bit data
from the MSM. It also consists a DC-DC converter
to supply -3.5V for fine view angle and LCD
reflector to improve the display efficiency.

5-1-3 Baseband Part

MOBILE STATION MODEM (MSM)

The MSM equipped with the INTEL 80186 CPU
core is an important component of the CDMA
cellular phone. The MSM comes in a 176 pins
TQFP package.

MICROPROCESSOR INTERFACE

The interface circuitry consists of reset circuit,
address bus (A0-A19), data bus (AD0-AD15), and
memory controls (ALE, DT_R, HWR/, LWR/,
RAM_CS/, ROM_CS etc).

INPUT CLOCK

CPU clock: 27 MHz
TCXO/4 (pin 34): 4.92 MHz. This clock signal
from the BBA is the reference clock for the MSM
except in CDMA mode.
CHIPX8 : 9.8304 MHz. The reference clock used
during the CDMA mode.

BBA INTERFACE

CDMA, FM Data Interface

TXIQDATA0-7 (pins 24-32) : TX data bus used
during both CDMA and FM mode but it is used
only for CDMA mode at this phone.

Clock

TC_CLK (pin 22), TX_CLK/(pin 23) : Digital to
Anolog Converter (DAC) reference clock used in
CDMA TX mode.
CHIPX8 : ADC reference clock used in CDMA
RX mode.

ADC Interface

ADC_CLK (pin 3), ADC_ENABLE (pin 1) and
ADC_DATA (pin 2) are required to control the
internal ADC in the BBA.

Data Port Interface

Includes the UART. Also, supports Diagnostic
Monitor (DM), HP equipment interface, down
loading, and data service.

CODEC Interface

The MSM sends 2.048 MHz PCM_CLK (pin 19)
and 8 KHz PCM_SYNC (pin 16, 20) to the CODEC
(U117). The voice PCM data from the MSM (U101)
PCM_DIN (pin 135) is compressed into 8 KHz, by
QCELP algorithm in the CDMA mode.

RF Interface

TX : TX_AGC_ADJ (pin 35) port is used to control
the TX power level and PA_ON (pin 44) signal is
used to control the power amplifier. This signal
depends on the TX vocoder rate.

RX : AGC_REF (pin 36) port is used to control the
RX gain and TRK_LO_ADJ (pin 45) is used to
compensate the TCXO clock.

General Purpose I/O Register Pins

Input/output ports to control external devices.

Power Down Control

When the IDLE/ signal turns to LOW, only the TX
sections will be disabled. If both the IDLE/ and
SLEEP/ change to LOW, all the pins except for the
TCXO and 27MHz clock are disabled.

5-1-4 Audio Part

TX AUDIO PATH

The voice signal output from microphone is
filtered and amplified by the internal OP-AMP
and is converted to PCM data by the CODEC
(U117). The signal is then applied to the MSM
(U101)’s internal vocoder.

RX AUDIO PATH

The PCM data from the MSM’s converted to audio
signal by ADC of CODEC (U117), is then
amplified by the speaker amplifer (U111) to be
sent to the speaker unit.

TX WBD, ST,SAT

These signals are generated from MSM. The
modulation level of TX WBD and ST is 8

kHz/dev, and SAT is 2 kHz/dev.

BUZZER DRIVING CIRCUITRY

Buzzer generates alert tone when the buzzer
receives the timer signal from the MSM, it
generates alert tone. The buzzer level is adjusted
by the alert signal’s period generated from the
MSM timer.

KEY TONE GENERATION

Ringer signal (pin49) out from MSM (U101) is
passed through 2 serial LPF consisting of R141,
C146, R145, and C142 amplified at the speaker
amp (U111), and comes out to speaker.

5-2 Receiver Section

LOW NOISE AMPLIFIER (LNA, Q302)

The low noise amplifier amplifies a weak signal
received from the base station to obtain the
optimum level (Noise figure = 1.5 dB,
Gain = 16 dB).

RADIO FREQUENCY BAND PASS FILTER
(RF BPF, F302)

The RF BPF accepts only a specific frequency (881

12.5 MHz) from the signal received from the

base station. The band width is 25 MHz.

DOWN CONVERTER (MIXER, U301)

First local signal is applied to this down converter.
The down converter transfers the signal amplified
at the LNA into 85.38 MHz IF signal. 85.38 MHz IF
signal is made by subtracting 881 12.5 MHz RF
signal from 966 12.5 MHz first local signal.

AUTOMATIC GAIN CONTROLLER (AGC)
AMP (Q302)

85.38 MHz IF signal is applied to IF AGC amp, the
IF AGC output level is applied to BBA (Baseband
Analog ASIC). The IF AGC amp (Q302) keeps the
signal at a constant level by controlling the gain.
Dynamic range is 90dB, up gain +45dB, and down
gain -45dB.

IF SAW BAND PASS FILTER (FOR CDMA)

IF SAW BPF (F303) is used for CDMA system
having 1.23 MHz wideband and 630 kHz
bandwidth. The filter also attenuates the image
product generated at the mixer.

BUFFER AMP (Q304)

Buffer (Q304) amplifiers signal to be applied to the
local input of the down converter (U301) when a
phase is locked between VCO (U341) and PLL IC
(U342).

VOLTAGE CONTROLLED OSCILLATOR (VCO,
U341)

The VCO (U341) generates the signal having 966
MHz center frequency and 12.5 MHz deviation

with the voltage control. PLL IC (U342) controls
this signal.

ANTENNA

Antenna allows signals and sends to receive from
the base station.

PHASE LOCKED LOOP (PLL, U342)

Input reference frequency is generated at
VC_TCXO (U343) and the divided signal is
generated at VCO. PLL compares the two signals
and generates the desired signal with a pre­programmed counter which controls voltage.

VOLTAGE CONTROLLED TEMPERATURE
COMPENSATED CRYSTAL OSCILLATOR (VC­TCXO, U343)

It provides 19.68 MHz reference frequency to PLL.
A correct frequency tuning is made by the voltage
control.

DUPLEXER (F301)

Duplexer (F301) controls to transmit through the
antenna only the signals within acceptable Tx
frequency range (836 12.5 MHz) and to receive
through the antenna only the signals within
acceptable Rx frequency range (881 12.5 MHz).
It also matches LNA input in receiving part and
PA output in transmitter part with the antenna.

POWER SUPPLY REGULATOR (U123)

The power supply regulator generates a regulated
power.

THERMISTOR (R498)

The thermistor (R498) detects temperature. It is
used to compensate active component
characteristics due to the temperature difference.