Maxim MAX5902-MAX5903 72v sot23 simple swapper hot-swap controller Datasheet

19-1988; Rev 1; 9/02
+72V SOT23 Simple Swapper Hot-Swap
Controllers
Features
♦ Wide +9V to +72V Operation
♦ Requires No External Sense Resistor
♦ Drives External P-Channel MOSFET
♦ Limits Inrush Current
♦ Circuit Breaker Function
♦ Less than 2mA Quiescent Current
♦ ON/OFF Input Permits Load Power-Supply
Control and Sequencing
♦ Adjustable Undervoltage Lockout
♦ Power-Good Output with +72V Rating
♦ Latching or Automatic Retry Fault Management
♦ Thermal Shutdown Helps Protect the External
MOSFET
♦ Space-Saving SOT23-6 Package
Ordering Information
PART
TEMP RANGE
PIN-PACKAGE
MAX5902_ _EUT*
-40°C to +85°C
6-SOT23
MAX5903_ _EUT*
-40°C to +85°C
6-SOT23
*For specific part numbers see Selector Guide at end of data
sheet.
Typical Operating Circuits
Applications
Network Routers
Network Switches
Servers
RAID
Base Station Line
Cards
Industrial Systems
50W ISOLATED
POWER SUPPLY
BACKPLANE CIRCUIT CARD
+48V
IRFR5410
HOT-SWAP CONTROLLER
Pin Configuration
MAX5902
VS
TOP VIEW
ON/OFF
VS 1
DRAIN 2
MAX5902
MAX5903
GATE 3
6
ON/OFF
5
PGOOD (PGOOD)
4
GND
GND
VIN (+)
LUCENT
JW050A1
GATE
DRAIN
PGOOD
ON/OFF
VIN (-)
GND
Typical Operating Circuits continued at end of data sheet.
SOT23-6
( ) ARE FOR MAX5903 ONLY.
Simple Swapper is a trademark of Maxim Integrated Products Inc.
________________________________________________________________ Maxim Integrated Products
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.
1
MAX5902/MAX5903
General Description
The MAX5902/MAX5903 are SOT23 hot-swap controllers that allow a circuit card to be safely hot plugged
into a live backplane without causing a glitch on the
power-supply rail. These devices operate from +9V to
+72V and provide the simplest hot-swap solution by
eliminating all external components except the external
P-channel MOSFET.
The MAX5902/MAX5903 limit the inrush current to the
load and provide a circuit breaker function for overcurrent protection. During startup the circuit breaker function is disabled and the MAX5902/MAX5903 limit the
inrush current by gradually turning on the external
MOSFET. Once the external MOSFET is fully enhanced,
the circuit breaker function is enabled and the
MAX5902/MAX5903 provide overcurrent protection by
monitoring the voltage drop across the external MOSFET’s on-resistance.
The MAX5902/MAX5903 include an undervoltage lockout (UVLO) function, ON/OFF control input and a
power-good status output, PGOOD (MAX5902) or
PGOOD (MAX5903). A built in thermal shutdown feature is also included to protect the external MOSFET in
case of overheating.
The MAX5902/MAX5903 offer latched or auto-retry fault
management and are available with 300mV, 400mV or
500mV circuit breaker thresholds. Both the MAX5902
and MAX5903 are available in a small SOT23 package,
and are specified for the extended -40°C to +85°C temperature range. For specific ordering information refer
to the selector guide at the end of the data sheet.
MAX5902/MAX5903
+72V SOT23 Simple Swapper Hot-Swap
Controllers
ABSOLUTE MAXIMUM RATINGS
Terminal Voltage (with respect to GND unless otherwise noted)
VS, DRAIN, PGOOD, PGOOD ................................-0.3V to +76V
ON/OFF ....................................................................-0.3V to +4V
GATE to VS ............................................................-12V to +0.3V
Current into any Pin ............................................................±3mA
Continuous Power Dissipation at TA = +70°C
6-Pin SOT23 (derate 9.1mW/°C above +70°C)..........727mW
Maximum Junction Temperature .....................................+150°C
Storage Temperature Range .............................-60°C to +150°C
Lead Temperature .............................................................Note 1
Note 1: This device is constructed using a unique set of packaging techniques that impose a limit on the thermal profile the device
can be exposed to during board level solder attach and rework. This limit permits only the use of solder profiles recommended in the industry standard specification, JEDEC 020A, paragraph 7.6, Table 3 for IR/VPR and convection reflow.
Preheating is required. Hand or wave soldering is not allowed.
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
(VS = +9V to +72V, GND = 0, ON/OFF open circuit, TA = -40°C to +85°C, unless otherwise noted. Typical values are at VS = +48V
and TA = +25°C.) (Notes 2, 3)
PARAMETER
Supply Voltage
SYMBOL
VS
CONDITIONS
Supply Current
IGND
Measured out of GND, PGOOD or PGOOD
open circuit, DRAIN = VS
External Gate Drive
VGS
VS - VGATE
Load Voltage Slew Rate
Magnitude
SR
| dVDRAIN/dt |
CL = 10µF
VUVLO
VS increasing
Default Undervoltage Lockout
MIN
9
MAX
72
UNITS
V
1
2
mA
11
VS = +36V to +72V
9
10
VS = +9V
8
8.5
VS = +36V to +72V
5
9
18
VS = +9V
3
6
11
28.5
31.5
34.5
Undervoltage Lockout
Hysteresis
3.5
ON/OFF Pin Input Resistance
RON/OFF
DRAIN to GND Resistance
RDGND
900
RDS
650
DRAIN to VS Resistance
ON/OFF Reference Threshold
VON/OFF
19
VON/OFF Increasing
tON
ON/OFF Off Delay (Note 5)
tOFF
VS - VGATE < 1V
Circuit Breaker Threshold
VCB
VS - VDRAIN
tCB
(VS - VDRAIN) > VCB
until (VS - VGATE)
< 1V, 200mV
overdrive step
V/ms
V
V
52
kΩ
kΩ
kΩ
1.26
1.38
80
150
280
ms
5
10
18
ms
MAX590_ _AEUT
200
300
460
MAX590_ _BEUT
280
400
540
MAX590_ _CEUT
400
500
660
CGATE = 1nF
2
6.5
CGATE = 4.7nF
4
11
CGATE = 10nF
7
17
150
280
ms
0.3
0.6
V
140
Start Delay (Note 4)
Circuit Breaker Delay (Note 6)
32
V
1.14
ON/OFF Hysteresis
2
TYP
Restart Delay (Note 4)
tRS
After circuit breaker event,
MAX590_ A_EUT only
Power Good Output Low Voltage
VOL
IOL = 1mA
80
_______________________________________________________________________________________
V
mV
mV
µs
+72V SOT23 Simple Swapper Hot-Swap
Controllers
(VS = +9V to +72V, GND = 0, ON/OFF open circuit, TA = -40°C to +85°C, unless otherwise noted. Typical values are at VS = +48V
and TA = +25°C.) (Notes 2, 3)
PARAMETER
SYMBOL
CONDITIONS
Power-Good Output Open-Drain
Leakage Current
IOH
V PGOOD = 72V (MAX5902)
V PGOOD = 72V (MAX5903)
Thermal Shutdown Temperature
TSD
Junction temperature
Thermal Shutdown Hysteresis
THY
MIN
TYP
MAX
UNITS
10
µA
+125
°C
15
°C
Note 2: All currents into device pins are positive, all currents out of device pins are negative, and all voltages are referenced to
GND, unless otherwise noted.
Note 3: All specifications are 100% tested at TA = +25°C, unless otherwise noted. Specifications over -40°C to +85°C are guaranteed by characterization.
Note 4: This is the delay time from a valid on condition until VGS begins rising. Valid on conditions are: the device is not in undervoltage lockout; ON/OFF is not driven low; and the device is not in thermal shutdown.
Note 5: This is the delay from a valid low on ON/OFF until VGS falls. Pulses on ON/OFF less than tOFF are ignored, offering glitch
immunity.
Note 6: Guaranteed by characterization, not production tested. CGATE is a capacitor from GATE to VS.
Typical Operating Characteristics
(VS = +48V, GND = 0, and TA = +25°C, unless otherwise noted. See Figure 2 for test circuits.)
SUPPLY CURRENT
vs. INPUT VOLTAGE
SUPPLY CURRENT
vs. TEMPERATURE
0.9
1.0
VIN = +12V
0.8
0.7
0.7
MAX5902 toc03
MAX5902 toc02
VIN = +48V
0.9
0.8
35
34
33
LOCKOUT VOLTAGE (V)
1.0
VIN = +70V
1.1
SUPPLY CURRENT (mA)
1.1
SUPPLY CURRENT (mA)
1.2
MAX5902 toc01
1.2
VUVLO THRESHOLD
vs. TEMPERATURE
INCREASING VIN
32
31
30
29
DECREASING VIN
28
27
26
0
15
30
45
INPUT VOLTAGE (V)
60
75
25
-40
-15
10
35
TEMPERATURE (°C)
60
85
-40
-15
10
35
60
85
TEMPERATURE (°C)
_______________________________________________________________________________________
3
MAX5902/MAX5903
ELECTRICAL CHARACTERISTICS (continued)
Typical Operating Characteristics (continued)
(VS = +48V, GND = 0, and TA = +25°C, unless otherwise noted. See Figure 2 for test circuits.)
GATE DRIVE VOLTAGE
vs. INPUT VOLTAGE
TURN-ON WAVEFORMS
RL = 60Ω, CL = 100µF
RETRY TIMEOUT
vs. TEMPERATURE
200
TIMEOUT PERIOD (ms)
13
11
9
7
MAX5902 toc05
225
MAX5902 toc04
15
GATE DRIVE (V)
MAX5902/MAX5903
+72V SOT23 Simple Swapper Hot-Swap
Controllers
0
B
175
0
150
C
0
125
D
100
0
75
5
0
15
30
45
60
-40
75
-15
10
35
60
TURN-ON WAVEFORMS
RL = OPEN, CL = 100µF
A : VOUT, 50V/div
B : IIN, 1A/div
C : VGATE, 50V/div
D : VIN, 50V/div
TURN-ON WAVEFORMS
RL = 60Ω, CL = 10µF MAX5902 toc08
MAX5902 toc07
TURN-ON WAVEFORMS
RL = 60Ω, CL = 100µF MAX5902 toc09
0
0
0
B
B
B
0
0
C
0
C
C
0
0
0
t = 2ms/div
t = 2ms/div
t = 2ms/div
A : VOUT, 50V/div
B : IIN, 0.5A/div
C : VGATE, 20V/div
A : VOUT, 50V/div
B : IIN, 1A/div
C : VGATE, 20V/div
A : VOUT, 50V/div
B : IIN, 1A/div
C : VGATE, 20V/div
CIRCUIT BREAKER EVENT
VOVERDRIVE = 200mV, CGATE = 1000pF
CIRCUIT BREAKER EVENT
VOVERDRIVE = 20mV, CGATE = 1000pF
MAX5902 toc10
MAX5902 toc11
0
0
A
A
B
t = 20ms/div
A
A
A
85
TEMPERATURE (°C)
INPUT VOLTAGE (V)
0
0
B
0
0
C
C
4
MAX5902 toc06
A
t = 1µs/div
A : VDS, 0.5V/div
B : VGS, 10V/div
C : VPGOOD TO VS, 50V/div
t = 1µs/div
A : VDS, 0.5V/div
B : VGS, 10V/div
C : VPGOOD TO VS, 50V/div
_______________________________________________________________________________________
+72V SOT23 Simple Swapper Hot-Swap
Controllers
PIN
NAME
FUNCTION
MAX5902
MAX5903
1
1
VS
2
2
DRAIN
3
3
GATE
Gate Drive Output for External P-Channel MOSFET
4
4
GND
Ground Connection
5
—
PGOOD
Power Good Output. PGOOD is an N-channel, open-drain, active-low output,
referenced to GND.
—
5
PGOOD
Power Good Output. PGOOD is an N-channel, open-drain, active-high output,
referenced to GND.
ON/OFF
ON/OFF Control Input. ON/OFF is referenced to GND. Drive ON/OFF above 1.38V or
leave unconnected to enable the device. Drive ON/OFF below 1V to disable the device.
ON/OFF is also used to adjust the UVLO threshold. Internally clamped to nominally 3V
through a 1kΩ resistor. (See Figure 1.) (See Undervoltage Lockout in the Applications
section of this data sheet.)
6
6
Positive Supply Voltage Input and External P-Channel MOSFET Source Connection
Drain Sense Input for External P-Channel MOSFET. Connect DRAIN as close as
possible to the MOSFET’s drain and use wide circuit traces to assure good thermal
coupling between the MAX5902/MAX5903 and the MOSFET. See Layout Guidelines.
Detailed Description
The MAX5902/MAX5903 are integrated hot-swap controller ICs contained in 6-pin SOT23 packages. They
allow a board to be safely hot-plugged into a live backplane without causing a glitch on the power-supply rail.
They are well suited for +48V power systems allowing
cost-effective, simple, and compact design. The
MAX5902/MAX5903 operate from +9V to +72V to cover
a wide range of end equipment hot-swap needs. They
require only an external P-channel power MOSFET to
provide hot-swap control. Figure 1 shows a functional
block diagram of the MAX5902/MAX5903.
The MAX5902/MAX5903 controls an external P-channel
power MOSFET placed in the positive power-supply
pathway. When power is first applied, the MAX5902/
MAX5903 keep the MOSFET turned off. The
MAX5902/MAX5903 hold the MOSFET off indefinitely if
ON/OFF is held low, if the supply voltage is below the
undervoltage lockout level, or if the die temperature
exceeds +125°C. If none of these conditions exist for
150ms (typ), the MAX5902/MAX5903 begin to gradually
turn on the MOSFET. During this turn-on phase, the
MAX5902/MAX5903 slowly enhance the MOSFET,
allowing the voltage on the load, i.e. the drain of the
MOSFET, to rise at a rate of 9V/ms (typ). The inrush current to the load is thus limited to a level proportional to
the load capacitance, and the constant slew rate. After
the MOSFET is fully enhanced, and the load voltage is
MAX5902
MAX5903
VS
*
828kΩ
ON/OFF
1kΩ
*
34.5kΩ
3V
PGOOD
(PGOOD)
CONTROL
LOGIC
GND
GND
*900kΩ
GND
*650kΩ
DRAIN
GATE
( ) ARE FOR THE MAX5903 ONLY
* RELATIVE TOLERANCE ±1%, ABSOLUTE TOLERANCE ±50% (TYP)
Figure 1. Functional Block Diagram
settled to its final value, the MAX5902A/ MAX5903A and
MAX5902L/MAX5903L monitor the voltage drop across
the MOSFET. If the voltage drop exceeds the circuit
breaker threshold the MAX5902A/MAX5903A and
MAX5902L/MAX5903L turn off the MOSFET, discon-
_______________________________________________________________________________________
5
MAX5902/MAX5903
Pin Description
MAX5902/MAX5903
+72V SOT23 Simple Swapper Hot-Swap
Controllers
necting the load immediately. If no circuit breaker fault
exists, the MAX5902/MAX5903 assert the power-good
output. Then, if any of four conditions exist, the power
good output deasserts and the MAX5902/MAX5903
turn off the MOSFET. The four conditions are: the voltage across the MOSFET exceeds the circuit breaker
threshold; the supply voltage falls below the undervoltage lockout level; the die temperature exceeds
+125°C; or ON/OFF is forced low. After a circuit breaker fault, the MAX5902L/MAX5903L keep the MOSFET
off until the power is cycled, or the part is reset by toggling ON/OFF low for 10ms (typ). After a circuit breaker
fault, the MAX5902A/MAX5903A automatically restarts
in 150ms (typ). All versions automatically restart after a
VS
VIN
V
GATE
thermal fault, or an undervoltage shutdown, if the fault
condition goes away for at least 150ms (typ).
ON/OFF offers external control of the MAX5902/
MAX5903, facilitating power-supply sequencing, and
may also be used to change the undervoltage lockout
(UVL) level. UVLO keeps the external MOSFET
switched off as long as the input voltage is below the
desired level.
A power good output, PGOOD (MAX5902) or PGOOD
(MAX5903), asserts when the external MOSFET is fully
enhanced and the source-drain voltage is below the
circuit breaker threshold. PGOOD and PGOOD are
open-drain outputs referenced to GND, and can withstand up to +72V.
SCOPE
48V
MAX5902
ON/OFF
GND
SCOPE
50kΩ
DRAIN
VS
GATE
DRAIN
0 TO 0.5V
MAX5902A
PGOOD
ON/OFF
I
(a) SUPPLY CURRENT
GND
PGOOD
(d) RETRY TIMEOUT
SCOPE
SCOPE
IRFR5410
VS
DRAIN
SCOPE
SCOPE
50kΩ
VS
48V
V
VIN
GATE
MAX5902
ON/OFF
GND
PGOOD
GATE
DRAIN
RL
CL
MAX5902
V
ON/OFF
(b) VUVLO
GND
PGOOD
(d) STARTUP WAVEFORMS
SCOPE
50Ω
VS
V
VIN
GATE
DRAIN
V
MAX5902
ON/OFF
GND
SCOPE
48V
VS
DRAIN
50kΩ
PGOOD
MAX5902
ON/OFF
(b) GATE DRIVE VOLTAGE
GATE
GND
PGOOD
SCOPE
(d) CIRCUIT BREAKER EVENT
Figure 2. Test Circuits
6
_______________________________________________________________________________________
+72V SOT23 Simple Swapper Hot-Swap
Controllers
HOT-SWAP CONTROLLER
+24V
OPTIONAL
ON/OFF
R2
40.2kΩ
VS
MAX5902
MAX5903
ON/OFF
DGND
R1
3.01kΩ
Applications Information
GND
GND
Figure 3. Programmed +18V Lockout, with Optional Optocoupler
On/Off Control.
A thermal shutdown feature protects the external MOSFET by turning it off if the die temperature of the
MAX5902/MAX5903 exceeds +125°C. The MAX5902/
MAX5903 must be in good thermal contact with the
external MOSFET. See Layout Guidelines in the Applications section of the data sheet.
A circuit breaker function monitors the voltage across
the external MOSFET, VSD, and turns off the MOSFET if
VSD exceeds the circuit breaker threshold, VCB. The
circuit breaker function is enabled after the MOSFET is
fully enhanced. Three threshold voltage options are
available—300mV, 400mV, and 500mV. One version is
available with no circuit breaker function. Fault management for the MAX5902/MAX5903 is offered with two
different configurations; latched and automatic retry.
ON/OFF Control Input
The ON/OFF control input provides three functions:
external ON/OFF control; setting of the UVLO level; and
resetting after a circuit breaker event has caused the
MAX5902L/MAX5903L to turn off the external MOSFET.
Pulling ON/OFF to GND for at least 10ms (tOFF) forces
the MAX5902/MAX5903 to turn off the external MOSFET
(see Figure 3 for a circuit example). To reset the
MAX5902L/MAX5903L after a circuit breaker event, toggle ON/OFF to GND for at least 10ms (tOFF).
ON/OFF can be used to sequence power supplies.
Connecting a capacitor from ON/OFF to GND will delay
the rise of ON/OFF proportional to the capacitance and
input impedance of ON/OFF, typically 33kΩ (Figure 4).
The MAX5902/MAX5903 can be controlled by logic
level signals. Logic level signals of 3.3V or 1.8V may be
directly connected to ON/OFF. For 5V logic level control,
insert a series 47kΩ resistor as shown in Figure 5.
HOT-SWAP CONTROLLER #1
VS
VS
Latched Circuit Breaker
ON/OFF
After a circuit breaker trip event the latched
versions (MAX5902L/MAX5903L) drive GATE to
V S , turning off the external MOSFET, and PGOOD
(PGOOD) is deasserted. A latched off condition
needs to be reset by toggling ON/OFF low for at
least 10ms, or by cycling the power supply, VS.
C
GND
HOT-SWAP CONTROLLER #2
Automatic Retry Circuit Breaker
After a circuit breaker trip event the automatic retry
versions (MAX5902A/MAX5903A) drive GATE to VS,
turning off the external MOSFET, and PGOOD
(PGOOD) is deasserted. If the start conditions are met
for a full 150ms (tRS) the start sequence is re-initiated.
The start conditions are: the device is not in UVLO;
ON/OFF is not driven low; and the device is not in thermal shutdown.
MAX5902
MAX5903
VS
MAX5902
MAX5903
ON/OFF
2C
GND
GND
Figure 4. Power-Supply Sequencing
_______________________________________________________________________________________
7
MAX5902/MAX5903
No Circuit Breaker
For the versions without a circuit breaker, MAX5902N
(MAX5903N), PGOOD (PGOOD) are asserted when the
MOSFET is fully enhanced. Once powered up the
MAX5902N/MAX5903N ignore the MOSFET drain-tosource voltage for applications where a circuit breaker
function is not desired.
MAX5902/MAX5903
+72V SOT23 Simple Swapper Hot-Swap
Controllers
HOT-SWAP CONTROLLER
MAX5902
MAX5903
47kΩ
GND
MAX5902
100kΩ
ON/OFF
5V LOGIC
HOT-SWAP CONTROLLER
+9V TO +72V
VS
ON/OFF
GND
GND
LOGIC CONTROL OF 3.3V OR LESS MAY BE CONNECTED
DIRECTLY TO THE MAX5902/MAX5903. FOR 5V LOGIC
CONTROL INSERT A SERIES 47kΩ RESISTOR AS SHOWN.
Figure 6. Defeating Undervoltage Lockout
Figure 5. Logic Control
Turn-On and Turn-Off Delays
After power is applied, or ON/OFF is released, there is
a 150ms delay (tON) before the gate ramp is started.
This delay is also the automatic restart time delay.
In the event of a circuit breaker condition or an overtemperature fault condition, the turn-off delay is less
than 4µs. An undervoltage condition must exist for at
least 10ms (tOFF) before the MAX5902/MAX5903 turns
off the external MOSFET. ON/OFF must be held low for
at least 10ms (t OFF) before the MAX5902/MAX5903
turns off the external MOSFET. Turn-off delay minimizes
spurious shutdowns due to noisy signals or momentary
voltage spikes, as well as preventing accidental resetting of the circuit breaker latch (MAX5902L/MAX5903L).
Thermal Shutdown
A thermal shutdown feature helps protect the external
MOSFET. If the die temperature of the MAX5902/
MAX5903 exceeds +125°C, the MOSFET is turned off.
For accurate performance the MAX5902/MAX5903
must be in close thermal contact with the external MOSFET. See Layout Guidelines for information. Due to the
low power dissipation of the MAX5902/MAX5903, its
junction temperature will typically be within a few
degrees of the MOSFET. All versions of the MAX5902/
MAX5903 automatically restart from a temperature fault
when the junction temperature drops below +110°C.
Undervoltage Lockout
The MAX5902/MAX5903 turns off the external MOSFET
if the magnitude of the input voltage is below the level
set by ON/OFF for longer than 10ms (tOFF). If ON/OFF
is left unconnected, the lockout voltage (V UVLO )
defaults to 31.5V. VUVLO may also be set to any value
within the power-supply range by using external resis-
8
GND
tors. To set the lockout voltage to a value between +9V
and +72V use a resistor divider connected between VS
and GND, with the center node of the divider connected to ON/OFF. For example, use a 3kΩ resistor (R1 in
Figure 3) from ON/OFF to GND and calculate the other
resistor, R2, using:
 V

R2 = R1 ×  UVLO − 1
 VON / OFF

where V UVLO is the desired lockout voltage, and
VON/OFF is the ON/OFF reference threshold specified in
the Electrical Characteristics table (typically 1.26V).
Figure 3 shows an example circuit with VUVLO set for
+18V. To defeat the UVLO simply connect a single
100kΩ resistor between ON/OFF and VS, as shown in
Figure 6.
The Power Good Output
The power good output, PGOOD (PGOOD), is opendrain and asserts when the external MOSFET is fully
enhanced and V SD is less than the circuit breaker
threshold (VCB). For versions without the circuit breaker
function (MAX5902N/MAX5903N), PGOOD (PGOOD)
asserts when the external MOSFET is fully enhanced.
PGOOD (PGOOD) deasserts within 4µs when a circuit
breaker event occurs or if the die temperature exceeds
+125°C. PGOOD (PGOOD) deasserts if VS < VUVLO for
longer than 10ms or ON/OFF is held low for longer than
10ms.
The MAX5902 PGOOD is active-low and the MAX5903
PGOOD is active-high. Both are open-drain N-channel
MOSFETs with their sources connected to GND, and
can withstand up to +72V.
_______________________________________________________________________________________
+72V SOT23 Simple Swapper Hot-Swap
Controllers
VCB > (RDS(ON)) ✕ (IOUT(MAX))
where RDS(ON) is the on-resistance of the MOSFET and
IOUT(MAX) is the maximum expected output current.
The MAX5902N/MAX5903N have no circuit breaker
function. For these parts choose an external MOSFET
which meets the load requirements.
The circuit breaker function is intended to protect
against gross overcurrent or short-circuit conditions.
During a gross overcurrent or short-circuit condition,
the MAX5902/MAX5903 disconnect the load by disabling the external MOSFET. For calculating the circuit
breaker threshold use the MOSFET’s RON at the worst
possible operating condition, and add a 20% overcurrent margin to the maximum circuit current. For
instance, if a MOSFET has an RON of 0.06Ω at TA =
+25°C, and a normalized on-resistance factor of 1.75 at
TA = +130°C (from the MOSFET data sheet), the RON
used for calculation is the product of these two numbers, or (0.06Ω) x (1.75) = 0.105Ω. Then, if the maximum current is expected to be 2A, using a 20%
margin, the current for calculation is (2A) x (1.2) = 2.4A.
The resulting minimum circuit breaker threshold is then
a product of these two results, or (0.105Ω) x (2.4A) =
0.252V. The next highest minimum available threshold
is 0.280V of the MAX5902ABEUT, which is an ideal
choice given these parameters. Using this method to
choose a circuit breaker threshold allows the circuit to
operate under worst case conditions without causing a
circuit breaker fault, but the circuit breaker function will
still operate if a short circuit, or a gross overcurrent
condition exists.
GROUND
U1
SOT23-6
MAX5902/MAX5903
POWER IN
M1
SOT-223
S D G
POWER
OUT
Figure 7. Circuit Board Layout Example.
Determining Inrush Current
Determining a circuit’s inrush current is necessary to
help choose the proper MOSFET. The MAX5902/
MAX5903 regulate the inrush current by means of controlling the load voltage slew rate, but inrush current is
also a function of load capacitance. Determine inrush
current using:
I=C
dV
= C × SR
dt
where C is the load capacitance, and SR is the
MAX5902/MAX5903 Load Voltage Slew Rate Magnitude
from the Electrical Characteristics table. For example,
assuming a load capacitance of 100µF, and using the
typical value of 9V/ms for the slew rate, the inrush current is 0.9A typical.
If the maximum possible Load Voltage Slew Rate is
used, the maximum inrush current calculates to 1.8A.
Choose a MOSFET with a maximum pulsed current
specification that exceeds the maximum inrush current.
Suggested External MOSFETs
MAXIMUM
ILOAD (A)
SUGGESTED
EXTERNAL
MOSFET
SUGGESTED MAXIM
PART
0.5
IRF9540NS
MAX5902AAEUT
1
IRF9540NS
MAX5902ABEUT
2
IRF5210S
MAX5902ABEUT
3
IRF5210S
MAX5902ACEUT
VIN = +9V to +72V
_______________________________________________________________________________________
9
MAX5902/MAX5903
Selecting a Circuit Breaker Threshold
The MAX5902A/MAX5903A and the MAX5902L/
MAX5903L offer a circuit breaker function to protect the
external MOSFET and the load from the potentially
damaging effects of excessive current. As load current
flows through the external MOSFET, a voltage, VSD, is
generated from source to drain due to the MOSFET’s
on-resistance, R DS(ON) . The MAX5902A/MAX5903A
and MAX5902L/MAX5903L monitor VSD when the external MOSFET is fully enhanced. If VSD exceeds the circuit breaker threshold the external MOSFET is turned
off, and PGOOD (PGOOD) is deasserted. To accommodate different MOSFETs and different load currents
the MAX5902/MAX5903 are available with circuit breaker threshold voltages of 300mV, 400mV, and 500mV. To
determine the proper circuit breaker threshold for an
application use:
MAX5902/MAX5903
+72V SOT23 Simple Swapper Hot-Swap
Controllers
Layout Guidelines
Chip Information
Good thermal contact between the MAX5902/
MAX5903 and the external MOSFET is essential for the
thermal shutdown feature to operate effectively. Place
the MAX5902/MAX5903 as close as possible to the
drain of the external MOSFET, and use wide circuit
board traces for good heat transfer. See Figure 7 for an
example of a PC board layout.
TRANSISTOR COUNT: 658
PROCESS TECHNOLOGY: BiCMOS
Selector Guide
CIRCUIT BREAKER
FUNCTION
CIRCUIT BREAKER
THRESHOLD
POWER GOOD
OUTPUT LOGIC
TOP MARK
MAX5902NNEUT*
None
None
Active-Low
AASM
MAX5902AAEUT*
Auto Retry
300mV
Active-Low
AASA
MAX5902ABEUT*
Auto Retry
400mV
Active-Low
AASB
MAX5902ACEUT*
Auto Retry
500mV
Active-Low
AASC
MAX5902LAEUT*
Latched
300mV
Active-Low
AASD
MAX5902LBEUT*
Latched
400mV
Active-Low
AASE
MAX5902LCEUT*
Latched
500mV
Active-Low
AASF
MAX5903NNEUT*
None
None
Active-High
AASN
MAX5903AAEUT*
Auto Retry
300mV
Active-High
AASG
MAX5903ABEUT*
Auto Retry
400mV
Active-High
AASH
MAX5903ACEUT*
Auto Retry
500mV
Active-High
AASI
MAX5903LAEUT*
Latched
300mV
Active-High
AASJ
MAX5903LBEUT*
Latched
400mV
Active-High
AASK
MAX5903LCEUT*
Latched
500mV
Active-High
AASL
PART
*Requires special solder temperature profile described in the Absolute Maximum Ratings section.
Typical Operating Circuits (continued)
50W ISOLATED
POWER SUPPLY
BACKPLANE CIRCUIT CARD
+48V
IRFR5410
HOT-SWAP CONTROLLER
V+
MAX5903
VS
ON/OFF
GND
1MΩ
GATE
DRAIN
PGOOD
MAX5003*
INDIV
39kΩ
GND
GND
*THE MAX5003 IS A 110V PWM CONTROLLER
10
______________________________________________________________________________________
+72V SOT23 Simple Swapper Hot-Swap
Controllers
6LSOT.EPS
Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are
implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.
Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 ____________________ 11
© 2002 Maxim Integrated Products
Printed USA
is a registered trademark of Maxim Integrated Products.
MAX5902/MAX5903
Package Information
(The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information
go to www.maxim-ic.com/packages.)
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