Samsung SCH-2000, Руководство по обслуживанию, Страница: 11 / 97

Samsung Electronics 4-1
4. Circuit Description
4-1 Logic Section
4-1-1 Power Supply
With the battery installed on the phone and by
pressing the PWR key, the VBATT and ON_SW
signals will be connected. This will turn on
Q109(2SC4081) and make gate port Low. VBAT
will be supplied to input if DC/DC converter,
controlled by Q115, makes 3.6V for Idle and Talk
Mode, and 3.4V for Sleep Mode.
The VBAT applied to ON_SW turns on
Q110(DTC144) and will result in the signal
ON_SW_SENSE to change state from HIGH to
LOW. The MSM recognizes this signal and sends
out PS_HOLD(logical HIGH) to turn on Q109 even
after the PWR key is released.
The power from U108 is used in the digital part of
MSM and BBA. The power from U111 is used in
the analog part of BBA.
4-1-2 Logic Part
The Logic part consists of internal CPU of MSM,
RAM, ROM and EEPROM. The MSM receives
TCXO/4 and CHIPX8 clock signals from the BBA
and controls the phone. The major components are
as follows:
¶U
CPU : INTEL 80186 core
¶U
FROM : U111,U114 (MBM29LV800T)-8MBIT
FLASH ROM
¶U
SRAM : U112(KM68FS2000I)-2MBIT STATIC
RAM
¶U
EEPROM : U107(24LC128I)-128KBIT SERIAL
EEPROM
CPU
INTEL 80186 CMOS type 16-bit microprocessor is
used and CPU controls all the circuitry. For the
CPU clock, 27MHz is used.
FLASH ROM (U111, U114)
One 8MBIT FROM(U111) is used to store the
terminal's program. Using the down-loading
program, the program can be changes even after
the terminal is fully assembled. The other is used
to store program for Voice memo, Voice dialing
and so on.
SRAM (U112)
One 2MBIT is used to store the internal flag
information, call processing data, and time data.
EEPROM (U107)
One 128KBIT is used to store ESN, NAM, power
level, volume level, and telephone number.
KEY-PAD
For key recognition, key matrix is setup using
SCAN0-6 of STROBE signals and KEY0-2 of input
ports of MSM. Six LEDs and backlight circuitry are
included in the keypad for easy operation in the
dark and it senses the six LEDs and backlight flip
ON/OFF through reed switch.
EARPIECE
This is a phone that can make a call and receive a
call by earpiece.
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 negative voltage for fine view angle and
LCD reflector to improve the display efficiency.