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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
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
ORing MOSFET Controllers with Fastest
Fault Isolation for Redundant Power Supplies
________________________________________________________________ Maxim Integrated Products
1
MAX8535
MAX8536
MAX8585
GATE
CS
FAULT
UVP
OVP
GND
TIMER
V
CC
SILVER BOX
OR
RECTIFIERS
OUT+
OUT-
REDUNDANT OUTPUT BUS
+V
O
-V
O
N.C.
OUTPUT:
3.3V/5V
(MAX8536),
12V
(MAX8535)
Typical Operating Circuit
Ordering Information
19-2735; Rev 1; 3/04
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.
PART
TEMP RANGE
PIN-PACKAGE
MAX8535
EUA
-40°C to +85°C
8 µMAX
MAX8535AEUA
-40°C to +85°C
8 µMAX
MAX8536
EUA
-40°C to +85°C
8 µMAX
MAX8585
EUA
-40°C to +85°C
8 µMAX
Pin Configuration, Functional Diagrams, and Typical
Application Circuits appear at end of data sheet.
EVALUATION KIT
AVAILABLE
MAX8535/MAX8536/MAX8585
ORing MOSFET Controllers with Fastest
Fault Isolation for Redundant Power Supplies
2
_______________________________________________________________________________________
ABSOLUTE MAXIMUM RATINGS
ELECTRICAL CHARACTERISTICS
(V
CC
= 12V (MAX8535/MAX8535A/MAX8585), V
CC
= 5V (MAX8536), V
CS
= V
CC
- 0.1V, R
TIMER
= 25k
, UVP = 2V, OVP = 1V, C
GATE
= 0.01µF,
T
A
= 0°C to +85°C
, unless otherwise noted.)
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.
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
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
V
CC
SUPPLY
V
CC
= 14V (MAX8535/
MAX8535A/MAX8585)
2
4.5
V
CC
Supply Current
TIMER = 2.5V
V
CC
= 6V (MAX8536)
2
3
mA
V
CC
= 14V (MAX8535/
MAX8535A/MAX8585)
4.5
V
CC
Shutdown Current
TIMER = 0V
V
CC
= 6V (MAX8536)
3
mA
MAX8535/MAX8535A/
MAX8585, charge pump on
8
14
MAX8536, charge pump on
3.0
5.5
V
CC
Input Voltage
TIMER = 2.5V
MAX8535/MAX8535A/
MAX8585, charge pump off
17
V
CS = 14V (MAX8535/
MAX8535A/MAX8585)
100
CS Input Current
TIMER = 2.5V
CS = 5.5V (MAX8536)
50
µA
CS Isolation
C S = m ax op er ati ng vol tag e, V
C C
= 0V , I( V
C C
) -0.05
-1
µA
MAX8535/MAX8535A/MAX8585, rising
threshold
6
6.5
7
V
CC
Undervoltage Lockout
V
CCOK
MAX8536, rising threshold
2.5
2.7
2.9
V
Rising threshold
14
14.5
15
V
CC
Overvoltage Internal
Threshold
MAX8535/
MAX8535A/
MAX8585
Falling threshold
13.3
13.9
14.5
V
CHARGE-PUMP VOLTAGE
Measured from V
GATE
to V
CC
, V
CC
= 3.3V
(MAX8536)
5
5.5
6
V
CC
= 5V (MAX8536)
5
5.5
6
Gate Voltage
V
GATE
V
C C
= 12V ( M AX 8535/M AX 8535A/M AX 8585)
9
11
12
V
MAX8535/MAX8536/MAX8585
ORing MOSFET Controllers with Fastest
Fault Isolation for Redundant Power Supplies
_______________________________________________________________________________________
3
ELECTRICAL CHARACTERISTICS (continued)
(V
CC
= 12V (MAX8535/MAX8535A/MAX8585), V
CC
= 5V (MAX8536), V
CS
= V
CC
- 0.1V, R
TIMER
= 25k
, UVP = 2V, OVP = 1V, C
GATE
= 0.01µF,
T
A
= 0°C to +85°C
, unless otherwise noted.)
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
R
TIMER
= 20k
187
R
TIMER
= 125k
450
R
TIMER
= open
500
Charge-Pump Switching
Frequency
V
TIMER
= 1.5V
550
kHz
TIMER
TIMER Voltage
1.219
1.25
1.281
V
TIMER Maximum Source Current
V
TIMER
= 1V
80
100
120
µA
TIMER High-Input Current
V
TIMER
= 1.5V
10
20
µA
MAX8535/MAX8535A/MAX8585
1.5
3.4
TIMER Maximum Frequency
Select Voltage Input Range
MAX8536
1.5
V
CC
- 0.6
V
TIMER Logic High
V
IH
Charge pump enabled
1.0
V
TIMER Logic Low
V
IL
Charge pump disabled
0.5
V
FAULT
Fault Output Low Voltage
I
FAULT
= 0.5mA
0.8
V
Fault Sink Current
FAULT = 0.8V
0.5
mA
FAULT = 18V ( MAX 8535 /MAX 8535A/MAX 8585)
5
Fault Leakage Current
FAULT = 6V (MAX8536)
5
µA
GATE
Gate On Threshold
Measured from V
CC
to CS
0.3
0.4
0.5
V
I
TIMER
= 0µA (MAX8535/
MAX8535A/MAX8585)
35
50
65
V
GATE
=
V
CC
= 12V
I
TIMER
= 50µA (MAX8535/
MAX8535A/MAX8585)
15
25
36
I
TIMER
= 0µA (MAX8536)
17
25
33
Gate Drive Current
V
GATE
=
V
CC
= 5V
I
TIMER
= 50µA (MAX8536)
8
12
16
µA
Gate Shutdown Delay
From fault sense to the start of gate voltage
falling, or from TIMER to the start of gate
voltage falling
200
300
ns
GATE = V
CC
+ 5V (MAX8535/MAX8536)
100
200
300
Gate Discharge Current
GATE = V
CC
+ 5V (MAX8535A/MAX8585)
200
300
400
mA
G ate vol tag e fal l fr om faul t to V
GAT E
= V
C C
,
C
GAT E
= 0.01µF ( 200ns + C V /I = 700ns, typ )
(MAX8535/MAX8536)
0.7
Gate Fall Time
MAX8535A/MAX8585
0.55
µs
CURRENT SENSE
Measured from CS to V
CC
(MAX8535/MAX8535A/MAX8536)
20
30
40
Reverse-Current Threshold
MAX8585
-3
0
+3
mV
MAX8535/MAX8536/MAX8585
ORing MOSFET Controllers with Fastest
Fault Isolation for Redundant Power Supplies
4
_______________________________________________________________________________________
ELECTRICAL CHARACTERISTICS
(V
CC
= 12V (MAX8535/MAX8535A/MAX8585), V
CC
= 5V (MAX8536), V
CS
= V
CC
- 0.1V, R
TIMER
= 25k
, UVP = 2V, OVP = 1V, C
GATE
= 0.01µF,
T
A
= -40°C to +85°C
, unless otherwise noted.) (Note 1)
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
V
CC
SUPPLY
V
CC
= 14V (MAX8535/
MAX8535A/MAX8585)
4.5
V
CC
Supply Current
TIMER = 2.5V
V
CC
= 6V (MAX8536)
3
mA
V
CC
= 14V (MAX8535/
MAX8535A/MAX8585)
4.5
V
CC
Shutdown Current
TIMER = 0V
V
CC
= 6V (MAX8536)
3
mA
MAX8535/MAX8535A/
MAX8585, charge pump on
8
14
MAX8536, charge pump on
3.0
5.5
V
CC
Input Voltage
TIMER = 2.5V
MAX8535/MAX8535A/
MAX8585, charge pump off
17
V
CS Isolation
C S = m ax op er ati ng vol tag e, V
C C
= 0V , I( V
C C
)
-1
µA
(MAX8535/MAX8535A/MAX8585) rising
threshold
6.0
7.0
V
CC
Undervoltage Lockout
V
CCOK
(MAX8536) rising threshold
2.5
2.9
V
Rising threshold
14
15
V
CC
Overvoltage Internal
Threshold
(MAX8535/
MAX8535A/
MAX8585)
Falling threshold
13.3
14.5
V
ELECTRICAL CHARACTERISTICS (continued)
(V
CC
= 12V (MAX8535/MAX8535A/MAX8585), V
CC
= 5V (MAX8536), V
CS
= V
CC
- 0.1V, R
TIMER
= 25k
, UVP = 2V, OVP = 1V, C
GATE
= 0.01µF,
T
A
= 0°C to +85°C
, unless otherwise noted.)
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
TIMER = open (MAX8535/MAX8535A/
MAX8536)
524
Startup Reverse-Current Blank
Time
MAX8585
32
ms
Forward-Current Threshold
Measured from V
CC
to CS
5
10
15
mV
OVERVOLTAGE PROTECTION
OVP rising
1.219
1.25
1.281
OVP Fault Threshold
V
OVP
OVP falling
1.2
V
OVP
Bias Current
0.2
µA
UNDERVOLTAGE PROTECTION
UVP rising threshold
1.219
1.25
1.281
UVP Fault Voltage
V
UVP
UVP falling threshold
1.119
1.15
1.181
V
UVP
Bias Current
0.4
µA
MAX8535/MAX8536/MAX8585
ORing MOSFET Controllers with Fastest
Fault Isolation for Redundant Power Supplies
_______________________________________________________________________________________
5
ELECTRICAL CHARACTERISTICS (continued)
(V
CC
= 12V (MAX8535/MAX8535A/MAX8585), V
CC
= 5V (MAX8536), V
CS
= V
CC
- 0.1V, R
TIMER
= 25k
, UVP = 2V, OVP = 1V, C
GATE
= 0.01µF,
T
A
= -40°C to +85°C
, unless otherwise noted.) (Note 1)
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
CHARGE-PUMP VOLTAGE
Measured from V
GATE
to V
CC
, V
CC
= 3.3V
(MAX8536)
5
6
V
CC
= 5V (MAX8536)
5
6
Gate Voltage
V
GATE
V
C C
= 12V ( M AX 8535/M AX 8535A/M AX 8585) 9
12
V
TIMER
TIMER Voltage
1.200
1.281
V
TIMER Maximum Source Current
V
TIMER
= 1.0V
80
120
µA
TIMER High-Input Current
V
TIMER
= 1.5V
20
µA
MAX8535/MAX8535A/MAX8585
1.5
3.4
TIMER Maximum Frequency
Select Voltage Input Range
MAX8536
1.5
V
CC
- 0.6
V
TIMER Logic High
V
IH
Charge pump enabled
1.1
V
TIMER Logic Low
V
IL
Charge pump disabled
0.5
V
FAULT
Fault Output Low Voltage
I
FAULT
= 0.5mA
0.8
V
Fault Sink Current
FAULT = 0.8V
0.5
mA
FAULT = 18V (MAX8535/
MAX8535A/MAX8585)
5
Fault Leakage Current
FAULT = 6V (MAX8536)
5
µA
GATE
Gate On Threshold
Measured from V
CC
to CS
0.3
0.5
V
I
TIMER
= 0µA (MAX8535/
MAX8535A/MAX8585)
35
65
V
GATE
=
V
CC
= 12V
I
TIMER
= 50µA (MAX8535/
MAX8535A/MAX8585)
15
36
I
TIMER
= 0µA (MAX8536)
17
33
Gate-Drive Current
V
GATE
=
V
CC
= 5V
I
TIMER
= 50µA (MAX8536)
8
16
µA
Gate Shutdown Delay
From fault sense to the start of gate voltage
falling, or from TIMER to the start of gate
voltage falling
300
ns
GATE = V
CC
+ 5V (MAX8535/MAX8536)
100
300
Gate Discharge Current
MAX8535A/MAX8585
200
400
mA
CURRENT SENSE
Measured from CS to V
CC
(MAX8535/MAX8535A/MAX8586)
20
40
Reverse-Current Threshold
MAX8585
-5
+5
mV
Forward-Current Threshold
Measured from V
CC
to CS
5
15
mV
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