The ISL6144 ORing MOSFET Controller and a suitably sized

N-Channel power MOSFET(s) increases power distribution

efficiency and availability when replacing a power ORing diode

in high current applications.

In a multiple supply, fault tolerant, redundant power distribution

system, paralleled similar power supplies contribute equally to

the load current through various power sharing schemes.

Regardless of the scheme, a common design practice is to

include discrete ORing power diodes to protect against reverse

current flow should one of the power supplies develop a

catastrophic output short to ground. In addition, reverse current

can occur if the current sharing scheme fails and an individual

power supply voltage falls significantly below the others.

Although the discrete ORing diode solution has been used for

some time and is inexpensive to implement, it has some

drawbacks. The primary downside is the increased power

dissipation loss in the ORing diodes as power requirements for

systems increase. Another disadvantage when using an ORing

diode would be failure to detect a shorted or open ORing diode,

jeopardizing power system reliability. An open diode reduces

the system to single point of failure while a diode short might

pose a hazard to technical personnel servicing the system

while unaware of this failure.

The ISL6144 can be used in 9V to 75V systems having similar

power sources and has an internal charge pump to provide a

floating gate drive for the N-Channel ORing MOSFET. The High

Speed (HS) Comparator protects the common bus from

individual power supply shorts by turning off the shorted feed’s

ORing MOSFET in less than 300ns and ensuring low reverse

current.

An external resistor-programmable detection level for the HS

Comparator allows users to set the N-Channel MOSFET

“VOUT - VIN” trip point to adjust control sensitivity to power

supply noise.

The Hysteretic Regulating (HR) Amplifier provides a slow turnoff of the ORing MOSFET. This turn-off is achieved in less than

100μs when one of the sourcing power supplies is shutdown

slowly for system diagnostics, ensuring zero reverse current.

This slow turn-off mechanism also reacts to output voltage

droop, degradation, or power-down.

An open drain FAULT pin will indicate that a fault has occurred.

The fault detection circuitry covers different types of failures;

including dead short in the sourcing supply, a short of any two

ORing MOSFET terminals, or a blown fuse in the power

distribution path.

Features

• Wide Supply Voltage Range +9V to +75V

• Transient Rating to +100V

• Reverse Current Fault Isolation

• Internal Charge Pump Allows the use of N-Channel

MOSFET

• HS Comparator Provides Very Fast <0.3µs Response

Time to Dead Shorts on Sourcing Supply. HS Comparator

also has Resistor-adjustable Trip Level

• HR Amplifier allows Quiet, <100µs MOSFET Turn-off for

Power Supply Slow Shut Down

• Open Drain, Active Low Fault Output with 120µs Delay

• Provided in Packages Compliant to UL60950 (UL1950)

Creepage Requirements

• QFN Package:

- Compliant to JEDEC PUB95 MO-220

QFN - Quad Flat No Leads - Package Outline

- Near Chip Scale Package footprint, which improves

PCB efficiency and has a thinner profile

• Pb-Free (RoHS Compliant)

Applications

• ORing MOSFET Control in Power Distribution Systems

• N + 1 Redundant Distributed Power Systems

• File and Network Servers (12V and 48V)

• Telecom/Datacom Systems