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Circuit Description
2-
2
Modulation Spectrum
200kHz offset
30 kHz bandwidth
GSM
-35dBc
DCS
-35dBc
PCS
-35dBc
400kHz offset
30 kHz bandwidth
GSM
-66dBc
DCS
-65dBc
PCS
-66dBc
600kHz ~ 1.8MHz offset
30 kHz bandwidth
GSM
-75dBc
DCS
-68dBc
PCS
-75dBc
2. Baseband Circuit description of SGH-E630
1. PCF50601
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. LCD Backlight Brightness Controler (MAX1574)
The Backlight Brightness is controled by Main chip(OM6357_7) through the MAX1574 charge pump.
The MAX1574 charge pump drives three white LED's with regulated constant current for uniform
intensity.
The MAX1574 uses an external resistor to set the full scale 100% LED current. An enable input
(EN-"BACKLIGHT") is used for simple on/off control or can be pulsed repeatedly to set lower LED current in multiple
steps down to 5%. Once the desired brightness is set, the MAX1574 maintains constant LED current as long as EN is
kept high. If EN is kept low for more than 2ms, the MAX1574 enters shutdown.
When the LEDs are enabled by driving EN high, the MAX1574 goes through soft-start, bringing the LED current up to
I
LED_
. Dimming is then done by pulsing EN low (500ns to 500µs pulse width). Each pulse reduces the LED current by
10%, so after one pulse the LED current is 0.9 x I
LED
. The tenth pulse reduces the current by 5%, so the I
LED_
current
reduces from 0.1 x I
LED_
to 0.05x I
LED
. The eleventh pulse sets the LED current back to I
LED_
.
1.3. Clock Generato
r
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.