Rainbow-electronics MAX5079 User Manual download pdf

General Description

The MAX5079 ORing MOSFET controller replaces

ORing diodes in high-reliability redundant, parallel-con-

nected power supplies. Despite their low forward-volt-

age drop, ORing Schottky diodes cause excessive

power dissipation at high currents. The MAX5079

allows for the use of low-on-resistance n-channel power

MOSFETs to replace the Schottky diodes. This results

in low power dissipation, smaller size, and elimination

of heatsinks in high-power applications.

The MAX5079 operates from 2.75V to 13.2V and includes

a charge pump to drive the high-side n-channel MOSFET.

Operation down to 1V is possible if an auxiliary voltage of

at least 2.75V is available. When the controller detects a

positive voltage difference between IN and BUS, the

n-channel MOSFET is turned on. The MOSFET is turned

off as soon as the MAX5079 sees a negative potential at

IN with respect to the BUS voltage, and is automatically

turned back on when the positive potential is restored.

Under fault conditions, the ORing MOSFET’s gate is

pulled down with a 1A current, providing an ultra-fast

200ns turn-off. The reverse voltage turn-off threshold is

externally adjustable to avoid unintentional turn-off of the

ORing MOSFET due to glitches at IN or BUS caused by

hot plugging the power supply.

Additional features include an OVP flag to facilitate

shutdown of a failed power supply due to an overvolt-

age condition, and a PGOOD signal that indicates if V

is either below the undervoltage lockout or V

BUS

is in

an overvoltage condition. The MAX5079 operates over

the -40°C to +85°C temperature range and is available

in a space-saving 14-pin TSSOP package.

Applications

Paralleled DC-DC Converter Modules

N+1 Redundant Power Systems

Servers

Base-Station Line Cards

RAID

Networking Line Cards

Features

♦ 2.75V to 13.2V Input ORing Voltage

♦ 1V to 13.2V Input ORing Voltage with 2.75V Aux

Voltage Present

♦ 2A MOSFET Gate Pulldown Current During Fault

Condition

♦ Ultra-Fast 200ns, MOSFET Turn-Off During Fault

Condition

♦ Supply Undervoltage and Bus Overvoltage

Detection

♦ Power-Good (PGOOD) and Overvoltage (OVP)

Outputs for Fault Detection

♦ Space-Saving 14-Pin TSSOP Package

♦ -40°C to +85°C Operating Temperature Range

MAX5079

ORing MOSFET Controller with

Ultra-Fast 200ns Turn-Off

________________________________________________________________ Maxim Integrated Products 1

Ordering Information

PART TEMP RANGE

PIN-PACKAGE

MAX5079EUD -40°C to +85°C 14 TSSOP

19-3584; Rev 0; 2/05

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.

BUS

COMMON

GATE BUSIN

POWER SUPPLY 1

(PS1)

POWER SUPPLY 2

(PS2)

1V TO 13.2V

OUT1

OUT2

UVLO

OVI

GND

STH

AUXIN

>2.75V

FTH

PGOOD

BUS

STH

FTH

STH

EXT

BUS

C+ C-

OVP

GATE BUSIN

1V TO 13.2V

UVLO

OVI

STH

AUXIN

>2.75V

PGOOD

BUS

C+ C-

OVP

MAX5079

GNDFTH

SUB 75N 03-04

Typical Operating Circuit

Pin Configuration appears at end of data sheet.

1 2 3 4 5 6 ... 17 18

Summary of Contents

Page 1 - Ultra-Fast 200ns Turn-Off

General DescriptionThe MAX5079 ORing MOSFET controller replacesORing diodes in high-reliability redundant, parallel-con-nected power supplies. Despite

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MAX5079ORing MOSFET Controller with Ultra-Fast 200ns Turn-OffMaxim cannot assume responsibility for use of any circuitry other than circuitry entirely

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MAX5079ORing MOSFET Controller with Ultra-Fast 200ns Turn-Off_______________________________________________________________________________________ 9

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Rainbow-electronics MAX5079 User Manual

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