MAX8744 datasheet(1/36 Pages) MAXIM

No de pièce	MAX8744

Description	High-Efficiency, Quad Output, Main Power-Supply Controllers for Notebook Computers

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Fabricant	MAXIM [Maxim Integrated Products]

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For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at

1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com.

General Description

The MAX8744/MAX8745 are dual step-down, switch-

mode, power-supply (SMPS) controllers with synchro-

nous rectification, intended for main 5V/3.3V power

generation in battery-powered systems. Fixed-frequen-

cy operation with optimal interleaving minimizes input

ripple current from the lowest input voltages up to the

26V maximum input. Optimal 40/60 interleaving allows

the input voltage to go down to 8.3V before duty-cycle

overlap occurs, compared to 180° out-of-phase regula-

tors where the duty-cycle overlap occurs when the

input drops below 10V.

Output current sensing provides peak current-limit pro-

tection, using either an accurate sense resistor or using

lossless inductor DCR current sensing. A low-noise

mode maintains high light-load efficiency while keeping

the switching frequency out of the audible range.

An internal, fixed 5V, 100mA linear regulator powers up

the MAX8744/MAX8745 and their gate drivers, as well

as external keep-alive loads. When the main PWM reg-

ulator is in regulation, an automatic bootstrap switch

bypasses the internal linear regulator, providing current

up to 200mA. An additional adjustable linear-regulator

driver with an external pnp transistor may be used with

a secondary winding to provide a 12V supply, or pow-

ered directly from the main outputs to generate low-

voltage outputs as low as 1V.

Independent enable controls and power-good signals

allow flexible power sequencing. Voltage soft-start

gradually ramps up the output voltage and reduces

inrush current, while soft-shutdown gradually ramps the

output voltage down, preventing negative voltage dips.

The MAX8744/MAX8745 feature output undervoltage

and thermal-fault protection. The MAX8744 also

includes output overvoltage-fault protection.

The MAX8744/MAX8745 are available in a 32-pin, 5mm

x 5mm, thin QFN package. The exposed backside pad

improves thermal characteristics for demanding linear

keep-alive applications.

Applications

Main Power Supplies

2 to 4 Li+ Cell Battery-Powered Devices

Notebook and Subnotebook Computers

PDAs and Mobile Communicators

Features

♦ Fixed-Frequency, Current-Mode Control

♦ 40/60 Optimal Interleaving

♦ Internal BST Switches

♦ Internal 5V, 100mA Linear Regulator

♦ Auxiliary Linear-Regulator Driver (12V or

Adjustable Down to 1V)

♦ Dual Mode™ Feedback—3.3V/5V Fixed or

Adjustable Output Voltages

♦ 200kHz/300kHz/500kHz Switching Frequency

♦ Undervoltage and Thermal-Fault Protection

♦ Overvoltage-Fault Protection (MAX8744 Only)

♦ 6V to 26V Input Range

♦ 2V ±0.75% Reference Output

♦ Independent Enable Inputs and Power-Good

Outputs

♦ Soft-Start and Soft-Shutdown (Voltage Ramp)

♦ 8µA (typ) Shutdown Current

High-Efficiency, Quad Output, Main Power-

Supply Controllers for Notebook Computers

________________________________________________________________ Maxim Integrated Products

1

19-3796; Rev 0; 4/06

+Denotes lead-free package.

MAX8744

MAX8745

THIN QFN

5mm x 5mm

TOP VIEW

29

30

28

27

12

11

13

14

12

+

CSL3

45

6

7

23

24

22

20

19

18

CSH3

FB3

PGOOD5

CSL5

CSH5

FB5

3

21

31

10

FBA

SKIP

32

9

OUTA

FSEL

PGOOD3

26

15

BST5

BST3

25

16

DH5

8

17

DH3

Pin Configuration

Ordering Information

PART

TEMP RANGE

PIN-

PACKAGE

PKG

CODE

MAX8744ETJ+

-40°C to +85°C

32 Thin QFN

(5mm x 5mm)

T3255-4

MAX8745ETJ+

-40°C to +85°C

32 Thin QFN

(5mm x 5mm)

T3255-4

Dual Mode is a trademark of Maxim Integrated Products, Inc.

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