Samsung SGH-X620 Service Manual page 6

Circuit Description
Modulation Spectrum
2-2. Baseband Circuit description of SGH-X620
2-2-1. PCF50601
- Power Management
Ten low-dropout regulators designed specifically for GSM applications power the terminal and help ensure optimal system
performance and long battery life. A programmable boost converter provides support for 1.8V, 3.0VSIMs, while a self-
resetting, electronically fused switch supplies power to external accessories. Ancillary support functions, such as RTC
module and High Voltage Charge pump, Clock generator, aid in reducing both board area and system complexity.
I2C BUS serial interface provides access to control and configuration registers. This interface gives a microprocessor full
control of the PCF50601 and enables system designers to maximize both standby and talk times.
Supervisory functions. including a reset generator, an input voltage monitor, and a temperature sensor, support reliable
system design. These functions work together to ensure proper system behavior during start-up or in the event of a fault
condition(low microprocessor voltage, insufficient battery energy, or excessive die temperature).
-Backlight Brightness Modulator
The Backlight Brightness Modulator (BBM) contains a programmable Pulse-w
to modulate the intensity of a series of LED' s or to control a DC/DC converter that drives LCD backlight.
This phone (SGH-X620) use PWM control to contrast the backlight brightness.
r
- Clock Generato
The Clock Generator (CG) generates all clocks for internal and external usa
oscillator provides an accurate low clock frequency for the PCF50601 and ot
2-2-2. LCD Connector
LCD is consisted of main LCD(color 65K UFB LCD) and sub LCD (B/W LCD).
Chip select signals LCD_MAIN_CS and LCD_SUB_CS, can enable Each LCD. BACKLIGHT signal enables white LED
of main LCD. "LCD_RESET" signal initiates the reset process of the LCD.
16-bit data lines(HD(0)~HD(15)) transfers data and commands to LCD. Data and commands use "HA(1)" signal. If this
signal is low, inputs to LCD are commands. If it is high, inputs to LCD are data.
200kHz offset
30 kHz bandwidth
400kHz offset
30 kHz bandwidth
600kHz ~ 1.8MHz offset
30 kHz bandwidth
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GSM
DCS
GSM
DCS
GSM
DCS
2- 2
-35dBc
-35dBc
-66dBc
-65dBc
-75dBc
-68dBc
idth modulator (PWM) and FET
ge. The 32768 Hz crystal
her circuitry.