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SS8000G

APPLICATION INFORMATION (cont.)

Low Dropout Regulator ( LDOs ) and Reference

The SS8000 integrates seven LDOs that are optimized

for their given functions by balancing quiescent current,

dropout voltage, line/load regulation, ripple rejection,

and output noise.

Digital Core LDO (Vcore)

The digital core LDO is a regulator that can source

200mA (max) with 1.8V output voltage. It supplies the

baseband circuitry in the handset. The LDO is optimized

for very low quiescent current.

Digital IO LDO (Vio)

The digital I/O LDO is a regulator that can source

100mA (max) with 2.8V output voltage. It supplies the

baseband circuitry in the handset. The LDO is optimized

for very low quiescent current and will power up at the

same time as the digital core LDO.

Analog LDO (Va)

The analog LDO is a regulator that can source 150mA

(max) with 2.8V output voltage. It supplies the analog

sections of the baseband chipsets. The LDO is opti-

mized for low frequency ripple rejection in order to reject

the ripple coming from the RF power amplifier burst fre-

quency at 217kHz.

TCXO LDO (Vtcxo)

The TCXO LDO is a regulator that can source 20mA (max)

with 2.8V output voltage. It supplies the temperature com-

pensated crystal oscillator, which needs its own ultra low

noise supply and very good ripple rejection ratio.

RTC LDO (Vrtc)

The RTC LDO is a regulator that can source 200µA

(max) with 1.5V output voltage. It charges up a capaci-

tor-type backup coin cell to run the real-time clock mod-

ule. The LDO features the reverse current protection

and is optimized for ultra low quiescent current since it is

always on except when the battery voltage is below

2.5V.

Memory LDO (Vm)

The memory LDO is a regulator that can source 150mA

(max) with 1.8V or 2.8V output voltage, selected ac-

cording to the supply specs of the memory chips. It sup-

plies the memory circuitry in the handset. The LDO is

optimized for very low quiescent current and will power

up at the same time as the digital core LDO.

SIM LDO (Vsim)

The SIM LDO is a regulator that can source 20mA (max)

with 1.8V or 3.0V output voltage, selected according to

the supply specs of the subscriber identity modules (SIM)

card. It supplies the SIMs in the handset. The LDO is

controlled independently of the others LDO.

Reference Voltage Output (Vref)

The reference voltage output is a low noise, high PSRR

and high precision reference with a guaranteed accuracy

of 1.5% over temperature. It is used as an internal system

reference within the SS8000. However, to maintain ac-

curate specs on every LDO output voltage, it is important

to avoid loading the reference voltage and it should be

bypassed to GND with 100 nF minimum.

SIM Card Interface

The SIM card interface circuitry of the SS8000 meets

all ETSI and IMT-2000 SIM interface requirements. It

provides level shifting needs for the low-voltage GSM

controller to communicate with either 1.8V or 3V SIM

cards. All SIM cards contain a clock input, a reset input,

and a bi-directional data input/output. The clock and

reset inputs to SIM cards are level shifted from the sup-

ply of the digital IO (Vio) of the baseband chipset to the

SIM supply (Vsim). The bi-directional data bus is inter-

nally pulled high with a 20kohm resistor on the controller

side and with a 10kohm resistor on the SIM side.

All pins that connect to the SIM card (Vsim, SRST,

SCLK, SIO) withstand over 5kV of human-body-mode

ESD. In order to ensure proper ESD protection, careful

board layout is required.

Vibrator, Alerter, LED Switches

Three built-in open-drain output switches drive the vi-

brator motor, alerter beeper and LEDs in the handset.

Each switch is controlled by the baseband chipset with

enable pins. The LED switch can sink 150mA to drive up

to 10 LEDs simultaneously for backlight. The vibrator

switch can sink 250mA for a vibrator motor. The alerter

switch can sink 300mA to drive the beeper. All the

open-drain output switches are high impedance when

disabled.

12/06/2004 Rev.2.10