MAX8535 Datasheet, PDF (1/20 Pages) Maxim Integrated Products – ORing MOSFET Controllers with Fastest Fault Isolation for Redundant Power Supplies

19-2735; Rev 1; 3/04
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ORing MOSFET Controllers with Fastest
Fault Isolation for Redundant Power Supplies
General Description
Critical loads often employ parallel-connected power
supplies with redundancy in order to enhance system
reliability. The MAX8535/MAX8536/MAX8585 are highly
integrated but inexpensive MOSFET controllers that pro-
vide isolation and redundant power capability in high-reli-
ability systems. The MAX8535/MAX8585 are used in 12V
systems, and have an internal charge pump to drive the
gates of the n-channel pass elements to V_CC + 10V. The
MAX8536 is used in 3.3V and 5V systems, with a charge-
pump output of V_CC + 5V.
During startup, the MAX8535/MAX8536/MAX8585 moni-
tor the voltage drop across external MOSFETs. Once
V_CC approaches or exceeds the bus voltage, the
MOSFETs are turned on. The MAX8535/MAX8536/
MAX8585 feature a dual-purpose TIMER input. A single
external resistor from TIMER to ground sets the turn-on
speed of the external MOSFETs. Optionally, the TIMER
input can be used as a logic-enable pin. Once the
device is turned on, the MAX8535/MAX8536/MAX8585
monitor the load, protecting against overvoltage, under-
voltage, and reverse-current conditions.
Overvoltage and undervoltage fault thresholds are
adjustable and can be disabled. The current-limit trip
points are set by the external MOSFETs’ R_DS(ON),
reducing component count. An open-drain logic-low
fault output indicates if an overvoltage, undervoltage, or
reverse-current fault occurs.
All devices come in a space-saving 8-pin µMAX^®
package and are specified over the extended -40°C to
+85°C temperature range.
µMAX is a registered trademark of Maxim Integrated Products, Inc.
Applications
Silver Box Supplies for Servers
On-Board Redundant Power Supplies in Blade
Servers
Network/Telecom Power Supplies
Rectifiers
Redundant Power Supplies in High-Availability
Systems
Pin Configuration, Functional Diagrams, and Typical
Application Circuits appear at end of data sheet.
Features
♦ Simple, Integrated, and Inexpensive ORing
MOSFET Controller
♦ ORing MOSFET Drive for 12V
(MAX8535/MAX8585) and 3.3V or 5V
(MAX8536) Bus
♦ Eliminates ORing Diode Power Dissipation and
Reverse Leakage Current
♦ Provides N + 1 Redundant Supply Capability for
Highly Reliable Systems
♦ Isolates Failed Supply from Output Bus in <1µs
♦ Reverse-Current Flow Detection
♦ Programmable Soft-Start
♦ Logic-Enable Input
♦ Adjustable Overvoltage and Undervoltage Trip
Points
♦ Fault-Indicator Output
♦ Space-Saving 8-Pin µMAX Package
Ordering Information
PART
MAX8535EUA
MAX8535AEUA
MAX8536EUA
MAX8585EUA
TEMP RANGE
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
PIN-PACKAGE
8 µMAX
8 µMAX
8 µMAX
8 µMAX
Typical Operating Circuit
OUT+
OUTPUT:
3.3V/5V
(MAX8536),
12V
(MAX8535)
+VO -VO
SILVER BOX
OR
RECTIFIERS
OUT-
GATE
CS
VCC
FAULT
MAX8535
MAX8536
UVP
N.C.
MAX8585
TIMER
OVP
GND
________________________________________________________________ Maxim Integrated Products 1
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