Rainbow Electronics MAX5079 - Manual

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
IN
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 BUS IN
POWER SUPPLY 1
(PS1)
POWER SUPPLY 2
(PS2)
1V TO 13.2V
V OUT1
V OUT2
UVLO OVI
GND
U1
STH
AUXIN
>2.75V
FTH
PGOOD
V BUS
R STH
R FTH
R FTH
C STH
R STH C STH
C EXT
C EXT
C BUS
N1
V IN
C+ C-
OVP
GATE BUS IN
1V TO 13.2V
UVLO OVI
U2
STH
AUXIN
>2.75V
PGOOD
V BUS N2
V IN
C+ C-
OVP
MAX5079
MAX5079
GND FTH
SUB 75N 03-04
SUB 75N 03-04
Typical Operating Circuit
Pin Configuration appears at end of data sheet.