Circuit Description - Samsung SGH-E800 Service Manual

Circuit Description

2. Baseband Circuit description of SGH-E800
1. PCF50601 (U400)
1.1. 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, 3.0V, and 5.0V
SIMs, 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).
1.2. Backlight Brightness Modulator
The Backlight Brightness Modulator (BBM) contains a programmable Pulse-width modulator (PWM) and FET to
modulate the intensity of a series of LED's or to control a DC/DC converter that drives LCD backlight.
This phone (SGH-E800) use PWM control to contrast the backlight brigtness.
1.3. Clock Generator
The Clock Generator (CG) generates all clocks for internal and external usage. The 32768 Hz crystal oscillator
provides an accurate low clock frequency for the PCF50601 and other circuitry.
2. LCD Connector
LCD is consisted of main LCD(color 65K TFT LCD).
Chip select signals in the U500, LCD_CS, can enable LCD. BACKLIGHT signal enables white LED of main LCD.
These signal is from U400.
16-bit data lines(LD(0)~LD(15)) transfers data and commands to LCD. Data and commands use "RS" signal. If this signal
is high, Inputs to LCD are commands. If it is low, Inputs to LCD are data. The signal which informs the input or output
state to LCD, is required. But this system is not necessary this signal. So "L_WR" signal is used to write data or
commands to LCD. Power signals for LCD are "LCD_VDD".
3. IRDA
This system uses IRDA module, HSDL_3208, Agilent's. This has signals, "IRDA_DOWN"(enable signal), "RXD0"(input
data) and "TXD0"(output data). These signals are connected to OM6359. It uses two power signals. "VDD2" is used for
circuit and "VBAT" is used for LED.
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