MAX782CSLASHD datasheet(9/32 Pages) MAXIM

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Triple-Output Power-Supply

Controller for Notebook Computers

_______________________________________________________________________________________

+3.3V Supply

The +3.3V supply is produced by a current-mode PWM

step-down regulator using two small N-channel MOSFETs,

a catch diode, an inductor, and a filter capacitor.

Efficiency is greatly enhanced by the use of the second

MOSFET (connected from LX3 to PGND), which acts as

a synchronous rectifier. A 100nF capacitor connected

to BST3 provides the drive voltage for the high-side

(upper) N-channel MOSFET.

A current limit set by an external sense resistor prevents

excessive inductor current during start-up or under

short-circuit conditions. A soft-start capacitor can be

chosen to tailor the rate at which the output ramps up.

This supply can be turned on by connecting ON3 to

logic high, or can be turned off by connecting ON3 to

GND. All logic levels are TTL and CMOS compatible.

+5V Supply

The +5V output is produced by a current-mode PWM

step-down regulator similar to the +3.3V supply. This

supply uses a transformer primary as its inductor, the

secondary of which is used for the high-side (VDD)

supply. It also has current limiting and soft-start. It can

be turned off by connecting ON5 to GND, or turned on

by connecting ON5 to logic high.

The +5V supply’s dropout voltage, as configured in

Figure 1, is typically 400mV at 2A. As VIN approaches

5V, the +5V output gracefully falls with VIN until the VL

regulator output hits its undervoltage lockout threshold.

At this point, the +5V supply turns off.

The default frequency for both PWM controllers is

300kHz (with SYNC connected to REF), but 200kHz

may be used by connecting SYNC to GND or VL.

VPPA

DA0

DA1

DB0

DB1

BST3

DH3

LX3

DL3

CS3

FB3

SS3

ON3

ON5

SYNC

VPPB

VDD

BST5

DH5

LX5

DL5

CS5

FB5

SS5

D1-D3

Q1-Q3

2, 3, 4

8, 7, 6

GND

REF PGND

BATTERY INPUT

5.5V TO 30V

(NOTE 1)

VPP

CONTROL

INPUTS

µF

D1A

1N4148

µH

25m

Ω

+3.3V at 3A

C14

150

µF

150

µF

1N5819

0.01

µF

+3.3V ON/OFF

+5V ON/OFF

OSC SYNC

µF

4.7

µF

C11

µF

C10

µF

D1B

1N4148 C4

0.1

µF

EC11FS1

1:2.2

L2 10

µH

1N5819

20m

Ω

C12

2.2

µF

330

µF

+5V at 3A

0.01

µF

COMPARATOR SUPPLY INPUT

COMPARATOR INPUTS

COMPARATOR OUTPUTS

3.3V AT 5mA

+5V at 5mA

0V, 5V, 12V

+15V AT 300mA, SEE

HIGH-SIDE SUPPLY (VDD)

SECTION.

0V, 5V, 12V

MAX782

V+

C13

µF

N1- N4 = Si9410DY

NOTE 1: BATTERY VOLTAGE RANGE 6.5V to 30V

WITH COMPONENTS SHOWN

SEE

LOW-VOLTAGE (6-CELL) OPERATION SECTION.

NOTE 2: SEE FIGURE 5.

(NOTE 2)

0.1

µF

Figure 1. MAX782 Application Circuit

MAX782C/D Datasheet(PDF) 9 Page - Maxim Integrated Products

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