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Circuit Description

2) TX PART

Baseband IQ signal fed into offset PLL, this function is included inside of U404 chip.

SI4205 chip generates modulator signal which power level is about 1.5dBm and fed into Power Amplifier(U403).

The PA output power and power ramping are well controlled by Auto Power Control circuit. We use offset PLL below

Modulation Spectrum

2. Baseband Circuit description of SGH-N700

1) CSP2200B1

1. Power Management

Seven low-dropout regulators designed specifically for GSM applications power the terminal and help ensure optimal

system performance and long battery life. A programmable LDO provides support for 1.8V, 3.0V SIMs, while a

self-resetting, electronically fused switch supplies power to external accessories. Ancillary support functions, such as two

LED drivers and two call-alert drivers, aid in reducing both board area and system complexity. A four-wire serial interface

unit(SIU) provides access to control and configuration registers. This interface gives a microprocessor full control of the

CSP2200B1 and enables system designers to maximize both standby and talk times. Error reporting is provided via an

interrupt signal and status register. Supervisory functions. including a reset generator, an input voltage monitor, and a

thermal monitor, 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).

2. Battery Charge Management

A battery charge management block, incorporating an internal PMOS switch, and an 8-bit ADC, provides fast, efficient

charging of single-cell Li-Ion battery. Used in conjunction with a current-limited voltage source, this block safely

conditions near-dead cells and provides the option of having fast-charge and top-off controlled internally or by the system's

microprocessor.

3. Backlight LED Driver

The backlight LED driver is a low-side, programmable current source designed to control the brightness of the keyboard

illumination. LED1_DRV is controlled via LED1_[0:2] and can be programmed to sink from 15mA to 60mA in 7.5mA

steps. LED2_DRV is controlled via LED2_[0:2] and can be programmed to sink from 5mA to 40mA in 5mA steps.

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

-66dBc

-65dBc

-75dBc

-68dBc