19-2735; Rev 1; 3/04
KIT
ATION
EVALU
BLE
AVAILA
ORing MOSFET Controllers with Fastest
Fault Isolation for Redundant Power Supplies
General Description
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
MAX8535/MAX8536/MAX8585
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.
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
OUTPUT:
3.3V/5V
(MAX8536),
12V
(MAX8535)
+V
O
-V
O
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
SILVER BOX
OR
RECTIFIERS
V
CC
GATE
CS
OUT+
FAULT
TIMER
MAX8535
MAX8536
MAX8585
GND
UVP
OVP
N.C.
Pin Configuration, Functional Diagrams, and Typical
Application Circuits appear at end of data sheet.
OUT-
________________________________________________________________
Maxim Integrated Products
REDUNDANT OUTPUT BUS
1
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.
ORing MOSFET Controllers with Fastest
Fault Isolation for Redundant Power Supplies
MAX8535/MAX8536/MAX8585
ABSOLUTE MAXIMUM RATINGS
GATE to GND (MAX8535/MAX8535A/MAX8585)...-0.3V to +28V
V
CC
to GND (MAX8535/MAX8535A/MAX8585) .....-0.3V to +18V
CS,
FAULT
to GND
(MAX8535/MAX8535A/MAX8585) ......................-0.3V to +15V
GATE to GND (MAX8536) ............................ -0.3V to (V
CC
+ 6V)
V
CC
, CS,
FAULT
to GND (MAX8536) .......................-0.3V to +6V
OVP, UVP, TIMER to GND........................................-0.3V to +6V
Continuous Power Dissipation (T
A
= +70°C)
8-Pin µMAX (derate 4.5mW/°C above +70°C) .............362mW
Operating Temperature Range ...........................-40°C to +85°C
Storage Temperature Range .............................-65°C to +150°C
Junction Temperature .........................................………..+150°C
Lead Temperature (soldering, 10s) .................................+300°C
Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional
operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to
absolute maximum rating conditions for extended periods may affect device reliability.
ELECTRICAL CHARACTERISTICS
(V
CC
= 12V (MAX8535/MAX8535A/MAX8585), V
CC
= 5V (MAX8536), V
CS
= V
CC
- 0.1V, R
TIMER
= 25kΩ, UVP = 2V, OVP = 1V, C
GATE
= 0.01µF,
T
A
= 0°C to +85°C,
unless otherwise noted.)
PARAMETER
V
CC
SUPPLY
V
CC
Supply Current
TIMER = 2.5V
V
CC
= 14V (MAX8535/
MAX8535A/MAX8585)
V
CC
= 6V (MAX8536)
V
CC
Shutdown Current
TIMER = 0V
V
CC
= 14V (MAX8535/
MAX8535A/MAX8585)
V
CC
= 6V (MAX8536)
MAX8535/MAX8535A/
MAX8585, charge pump on
V
CC
Input Voltage
TIMER = 2.5V
MAX8536, charge pump on
MAX8535/MAX8535A/
MAX8585, charge pump off
CS Input Current
CS Isolation
V
CC
Undervoltage Lockout
V
CCOK
TIMER = 2.5V
CS = 14V (MAX8535/
MAX8535A/MAX8585)
CS = 5.5V (MAX8536)
CS = max operating voltage, V
CC
= 0V, I(V
CC
)
MAX8535/MAX8535A/MAX8585, rising
threshold
MAX8536, rising threshold
V
CC
Overvoltage Internal
Threshold
CHARGE-PUMP VOLTAGE
Measured from V
GATE
to V
CC
, V
CC
= 3.3V
(MAX8536)
Gate Voltage
V
GATE
V
CC
= 5V (MAX8536)
V
CC
= 12V (MAX8535/MAX8535A/MAX8585)
5
5
9
5.5
5.5
11
6
6
12
V
MAX8535/
MAX8535A/
MAX8585
Rising threshold
Falling threshold
6
2.5
14
13.3
100
50
-0.05
6.5
2.7
14.5
13.9
-1
7
2.9
15
V
14.5
µA
V
8
3.0
2
2
4.5
3
4.5
3
14
5.5
17
V
mA
mA
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
µA
2
_______________________________________________________________________________________
ORing MOSFET Controllers with Fastest
Fault Isolation for Redundant Power Supplies
ELECTRICAL CHARACTERISTICS (continued)
(V
CC
= 12V (MAX8535/MAX8535A/MAX8585), V
CC
= 5V (MAX8536), V
CS
= V
CC
- 0.1V, R
TIMER
= 25kΩ, UVP = 2V, OVP = 1V, C
GATE
= 0.01µF,
T
A
= 0°C to +85°C,
unless otherwise noted.)
PARAMETER
Charge-Pump Switching
Frequency
TIMER
TIMER Voltage
TIMER Maximum Source Current
TIMER High-Input Current
TIMER Maximum Frequency
Select Voltage Input Range
TIMER Logic High
TIMER Logic Low
FAULT
Fault Output Low Voltage
Fault Sink Current
Fault Leakage Current
GATE
Gate On Threshold
Measured from V
CC
to CS
V
GATE
=
V
CC
= 12V
I
TIMER
= 0µA (MAX8535/
MAX8535A/MAX8585)
I
TIMER
= 50µA (MAX8535/
MAX8535A/MAX8585)
I
TIMER
= 0µA (MAX8536)
I
TIMER
= 50µA (MAX8536)
0.3
35
15
17
8
0.4
50
25
25
12
200
100
200
200
300
0.7
0.55
0.5
65
36
33
16
300
300
400
ns
µA
V
I
FAULT
= 0.5mA
FAULT
= 0.8V
FAULT
= 18V (MAX8535 /MAX8535A/MAX8585)
FAULT
= 6V (MAX8536)
0.5
5
5
0.8
V
mA
µA
V
IH
V
IL
V
TIMER
= 1V
V
TIMER
= 1.5V
MAX8535/MAX8535A/MAX8585
MAX8536
Charge pump enabled
Charge pump disabled
1.5
1.5
1.0
0.5
1.219
80
1.25
100
10
1.281
120
20
3.4
V
CC
- 0.6
V
µA
µA
V
V
V
SYMBOL
R
TIMER
= 20kΩ
R
TIMER
= 125kΩ
R
TIMER
= open
V
TIMER
= 1.5V
CONDITIONS
MIN
TYP
187
450
500
550
kHz
MAX
UNITS
MAX8535/MAX8536/MAX8585
Gate Drive Current
V
GATE
=
V
CC
= 5V
Gate Shutdown Delay
From fault sense to the start of gate voltage
falling, or from TIMER to the start of gate
voltage falling
GATE = V
CC
+ 5V (MAX8535/MAX8536)
GATE = V
CC
+ 5V (MAX8535A/MAX8585)
Gate voltage fall from fault to V
GATE
= V
CC
,
C
GATE
= 0.01µF (200ns + CV/I = 700ns, typ)
(MAX8535/MAX8536)
MAX8535A/MAX8585
Gate Discharge Current
mA
Gate Fall Time
µs
CURRENT SENSE
Reverse-Current Threshold
Measured from CS to V
CC
(MAX8535/MAX8535A/MAX8536)
MAX8585
20
-3
30
0
40
+3
mV
_______________________________________________________________________________________
3
ORing MOSFET Controllers with Fastest
Fault Isolation for Redundant Power Supplies
MAX8535/MAX8536/MAX8585
ELECTRICAL CHARACTERISTICS (continued)
(V
CC
= 12V (MAX8535/MAX8535A/MAX8585), V
CC
= 5V (MAX8536), V
CS
= V
CC
- 0.1V, R
TIMER
= 25kΩ, UVP = 2V, OVP = 1V, C
GATE
= 0.01µF,
T
A
= 0°C to +85°C,
unless otherwise noted.)
PARAMETER
Startup Reverse-Current Blank
Time
Forward-Current Threshold
OVERVOLTAGE PROTECTION
OVP Fault Threshold
OVP Bias Current
UNDERVOLTAGE PROTECTION
UVP Fault Voltage
UVP Bias Current
V
UVP
UVP rising threshold
UVP falling threshold
1.219
1.119
1.25
1.15
1.281
1.181
0.4
V
µA
V
OVP
SYMBOL
CONDITIONS
TIMER = open (MAX8535/MAX8535A/
MAX8536)
MAX8585
Measured from V
CC
to CS
OVP rising
OVP falling
5
1.219
MIN
TYP
524
32
10
1.25
1.2
0.2
MAX
UNITS
ms
15
1.281
mV
V
µA
ELECTRICAL CHARACTERISTICS
(V
CC
= 12V (MAX8535/MAX8535A/MAX8585), V
CC
= 5V (MAX8536), V
CS
= V
CC
- 0.1V, R
TIMER
= 25kΩ, UVP = 2V, OVP = 1V, C
GATE
= 0.01µF,
T
A
= -40°C to +85°C,
unless otherwise noted.) (Note 1)
PARAMETER
V
CC
SUPPLY
V
CC
Supply Current
V
CC
= 14V (MAX8535/
TIMER = 2.5V MAX8535A/MAX8585)
V
CC
= 6V (MAX8536)
V
CC
Shutdown Current
TIMER = 0V
V
CC
= 14V (MAX8535/
MAX8535A/MAX8585)
V
CC
= 6V (MAX8536)
MAX8535/MAX8535A/
MAX8585, charge pump on
V
CC
Input Voltage
TIMER = 2.5V MAX8536, charge pump on
MAX8535/MAX8535A/
MAX8585, charge pump off
CS Isolation
V
CC
Undervoltage Lockout
V
CCOK
CS = max operating voltage, V
CC
= 0V, I(V
CC
)
(MAX8535/MAX8535A/MAX8585) rising
threshold
(MAX8536) rising threshold
V
CC
Overvoltage Internal
Threshold
(MAX8535/
MAX8535A/
MAX8585)
Rising threshold
Falling threshold
6.0
2.5
14
13.3
8
3.0
4.5
3
4.5
3
14
5.5
17
-1
7.0
2.9
15
V
14.5
µA
V
V
mA
mA
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
4
_______________________________________________________________________________________
ORing MOSFET Controllers with Fastest
Fault Isolation for Redundant Power Supplies
ELECTRICAL CHARACTERISTICS (continued)
(V
CC
= 12V (MAX8535/MAX8535A/MAX8585), V
CC
= 5V (MAX8536), V
CS
= V
CC
- 0.1V, R
TIMER
= 25kΩ, UVP = 2V, OVP = 1V, C
GATE
= 0.01µF,
T
A
= -40°C to +85°C,
unless otherwise noted.) (Note 1)
PARAMETER
CHARGE-PUMP VOLTAGE
Measured from V
GATE
to V
CC
, V
CC
= 3.3V
(MAX8536)
Gate Voltage
V
GATE
V
CC
= 5V (MAX8536)
V
CC
= 12V (MAX8535/MAX8535A/MAX8585)
TIMER
TIMER Voltage
TIMER Maximum Source Current
TIMER High-Input Current
TIMER Maximum Frequency
Select Voltage Input Range
TIMER Logic High
TIMER Logic Low
FAULT
Fault Output Low Voltage
Fault Sink Current
Fault Leakage Current
GATE
Gate On Threshold
Measured from V
CC
to CS
V
GATE
=
V
CC
= 12V
V
GATE
=
V
CC
= 5V
Gate Shutdown Delay
I
TIMER
= 0µA (MAX8535/
MAX8535A/MAX8585)
I
TIMER
= 50µA (MAX8535/
MAX8535A/MAX8585)
I
TIMER
= 0µA (MAX8536)
I
TIMER
= 50µA (MAX8536)
0.3
35
15
17
8
0.5
65
36
33
16
300
100
200
300
400
ns
µA
V
I
FAULT
= 0.5mA
FAULT
= 0.8V
FAULT
= 18V (MAX8535/
MAX8535A/MAX8585)
FAULT
= 6V (MAX8536)
0.5
5
5
0.8
V
mA
µA
V
IH
V
IL
V
TIMER
= 1.0V
V
TIMER
= 1.5V
MAX8535/MAX8535A/MAX8585
MAX8536
Charge pump enabled
Charge pump disabled
1.5
1.5
1.1
0.5
1.200
80
1.281
120
20
3.4
V
CC
- 0.6
V
µA
µA
V
V
V
5
5
9
6
6
12
V
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
MAX8535/MAX8536/MAX8585
Gate-Drive Current
From fault sense to the start of gate voltage
falling, or from TIMER to the start of gate
voltage falling
GATE = V
CC
+ 5V (MAX8535/MAX8536)
MAX8535A/MAX8585
Measured from CS to V
CC
(MAX8535/MAX8535A/MAX8586)
MAX8585
Measured from V
CC
to CS
Gate Discharge Current
CURRENT SENSE
Reverse-Current Threshold
Forward-Current Threshold
mA
20
-5
5
40
+5
15
mV
mV
_______________________________________________________________________________________
5
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