Samsung SGH-X450 Service Manual

Also see for SGH-X450: Quick guide Quick reference card

Contents

SAMSUNG Proprietary-Contents may change without notice2) TX PARTBaseband IQ signal fed into offset PLL, this function is included inside of U100 chip.SI4205 chip generates modulator signal which power level is about 1.5dBm and fed into Power Amplifier(U200).The PA output power and power ramping are well controlled by Auto Power Control circuit. We use offset PLL belowModulation Spectrum200kHz offset30 kHz bandwidthGSM -35dBcDCS -35dBcPCS -35dBc400kHz offset30 kHz bandwidthGSM -66dBcDCS -65dBcPCS -66dBc600kHz ~ 1.8MHz offset30 kHz bandwidthGSM -75dBcDCS -68dBcPCS -75dBc1) PSC21061. Power ManagementSeven low-dropout regulators designed specifically for GSM applications power the terminal and help ensure optimalsystem performance and long battery life.A programmable LDO provides support for 1.8V, 3.0V SIMs, while aself-resetting, electronically fused switch supplies power to external accessories. Ancillary support functions, such as twoLED drivers and two call-alert drivers, aid in reducing both board area and system complexity.A four-wire serial interfaceunit(SIU) provides access to control and configuration registers. This interface gives a microprocessor full control of thePSC2106 and enables system designers to maximize both standby and talk times. Error reporting is provided via aninterrupt signal and status register.Supervisory functions. including a reset generator, an input voltage monitor, and athermal monitor, support reliable system design. These functions work together to ensure proper system behavior duringstart-up or in the event of a fault condition(low microprocessor voltage, insufficient battery energy, or excessive dietemperature).2. Battery Charge ManagementA battery charge management block, incorporating an internal PMOS switch, and an 8-bit ADC, provides fast, efficientcharging of single-cell Li-Ion battery. Used in conjunction with a current-limited voltage source, this block safelyconditions near-dead cells and provides the option of having fast-charge and top-off controlled internally or by the system'smicroprocessor.