ADP3408(Rev0) 查看數據表（PDF） - Analog Devices

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ADP3408
(Rev.:Rev0)

GSM Power Management System

Analog Devices 

ADP3408

PWRON

PWRONKEY

KEYPADROW

GPIO

VRTC

AUXADC

GPIO

CHARGER IN

GPIO

CAPACITOR

TYPE BACKUP

COIN CELL

C1

0.1␮F

R1

0.33⍀

C2, 10nF

Q1

SI3441DY

D1

LI OR NIMH

BATTERY

PWRONIN

TCXOEN

PWRONKEY

AGND

ROWX

REFOUT

SIMEN

VTCXO

VRTCIN U1

VAN

ADP3408

VRTC

VBAT

BATSNS

VCORE

MVBAT

VMEM

CHRDET

VBAT2

CHRIN

VSIM

GATEIN

RESET

GATEDR

RESCAP

DGND

CHGEN

ISENSE

EOC

R2

10⍀

C3, 10␮F

C8

2.2␮F

C6

2.2␮F

C5

2.2␮F

C4

0.1␮F

C7

2.2␮F

C9

0.22␮F

CLKON

C10

0.1␮F

REF

VTCXO

VAN

VCORE

VMEM

VSIM

RESET

GPIO

GPIO

Figure 3. Typical Application Circuit

THEORY OF OPERATION

The ADP3408 is a power management chip optimized for use

with GSM baseband chipsets in handset applications. Figure 1

shows a block diagram of the ADP3408.

The ADP3408 contains several blocks:

• Six Low Dropout Regulators (SIM, Core, Analog, Crystal

Oscillator, Memory, Real-Time Clock)

• Reset Generator

• Buffered Precision Reference

• Lithium Ion Charge Controller and Processor Interface

• Power-On/-Off Logic

• Undervoltage Lockout

• Deep Discharge Lockout

These functions have traditionally been done either as a discrete

implementation or as a custom ASIC design. The ADP3408

combines the benefits of both worlds by providing an integrated

standard product where every block is optimized to operate in a

GSM environment while maintaining a cost competitive solution.

Figure 3 shows the external circuitry associated with the ADP3408.

Only a minimal number of support components are required.

Input Voltage

The input voltage range of the ADP3408 is 3 V to 5.5 V and is

optimized for a single Li-Ion cell or three NiMH cells. The

thermal impedance of the ADP3408 is 68°C/W for four-layer

boards. The end-of-charge voltage for high capacity NiMH cells

can be as high as 5.5 V. Power dissipation should be calculated

at maximum ambient temperatures and battery voltage in order

not to exceed the 125°C maximum allowable junction temperature.

Figure 4 shows the maximum power dissipation as a function of

ambient temperature.

However, high battery voltages normally occur only when the

battery is being charged and the handset is not in conversation

mode. In this mode there is a relatively light load on the LDOs.

A fully charged Li-Ion battery is 4.25 V, where the ADP3408

can deliver the maximum power (0.56W) up to 85°C ambient

temperature.

1.2

1.0

0.8

0.6

0.4

0.2

0.0

–20

0

20

40

60

80

100

AMBIENT TEMPERATURE – ؇C

Figure 4. Power Dissipation vs. Temperature

Low Dropout Regulators (LDOs)

The ADP3408 high-performance LDOs are optimized for their

given functions by balancing quiescent current, dropout voltage,

regulation, ripple rejection, and output noise. 2.2 µF tantalum

or MLCC ceramic capacitors are recommended for use with the

core, memory, SIM, and analog LDOs. A 0.22 µF capacitor is

recommended for the TCXO LDO.

REV. 0

–11–

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