MAX5903ABEUT [MAXIM]
Analog IC ; 模拟IC\n
| 型号： | MAX5903ABEUT |
| 厂家： | 
MAXIM INTEGRATED PRODUCTS |
| 描述： | Analog IC
|
| 文件： | 总11页 (文件大小：277K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
19-1988; Rev 0; 3/01
+72V SOT23 Simple Swapper Hot-Swap
Controllers
General Description
Features
The MAX5902/MAX5903 are SOT23 hot-swap con-
trollers 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.
o Wide +9V to +72V Operation
o Requires No External Sense Resistor
o Drives External P-Channel MOSFET
o Limits Inrush Current
o Circuit Breaker Function
The MAX5902/MAX5903 limit the inrush current to the
load and provide a circuit breaker function for overcur-
rent protection. During startup the circuit breaker func-
tion 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 MOS-
FET’s on-resistance.
o Less than 2mA Quiescent Current
o ON/OFF Input Permits Load Power-Supply
Control and Sequencing
o Adjustable Undervoltage Lockout
o Power-Good Output with +72V Rating
o Latching or Automatic Retry Fault Management
o Thermal Shutdown Helps Protect the External
The MAX5902/MAX5903 include an undervoltage lock-
out (UVLO) function, ON/OFF control input and a
power-good status output, PGOOD (MAX5902) or
PGOOD (MAX5903). A built in thermal shutdown fea-
ture is also included to protect the external MOSFET in
case of overheating.
MOSFET
o Space-Saving SOT23-6 Package
Ordering Information
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 tem-
perature range. For specific ordering information refer
to the selector guide at the end of the data sheet.
PART
TEMP. RANGE
-40°C to +85°C
-40°C to +85°C
PIN-PACKAGE
6-SOT23
MAX5902_ _EUT*
MAX5903_ _EUT*
6-SOT23
*For specific part numbers see Selector Guide at end of data
sheet.
Typical Operating Circuits
Applications
Network Routers
Network Switches
Servers
50W ISOLATED
RAID
BACKPLANE CIRCUIT CARD
POWER SUPPLY
IRFR5410
Base Station Line
Cards
Industrial Systems
+48V
HOT SWAP CONTROLLER
V
(+)
IN
LUCENT
JW050A1
MAX5902
GATE
Pin Configuration
V
S
TOP VIEW
ON/OFF
GND
DRAIN
PGOOD
ON/OFF
(-)
V
1
2
3
6
5
4
ON/OFF
S
V
IN
GND
MAX5902
MAX5903
DRAIN
GATE
PGOOD (PGOOD)
GND
Typical Operating Circuits continued at end of data sheet.
Simple Swapper is a trademark of Maxim Integrated Products Inc.
SOT23-6
( ) ARE FOR MAX5903 ONLY.
________________________________________________________________ Maxim Integrated Products
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.
+72V SOT23 Simple Swapper Hot-Swap
Controllers
ABSOLUTE MAXIMUM RATINGS
Terminal Voltage (with respect to GND unless otherwise noted)
Continuous Power Dissipation at T = +70°C
A
V , DRAIN, PGOOD, PGOOD ................................-0.3V to +76V
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
S
ON/OFF ....................................................................-0.3V to +4V
GATE to V ............................................................-12V to +0.3V
S
Current into any Pin ............................................................ 3mA
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 recom-
mended 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
(V = +9V to +72V, GND = 0, ON/OFF open circuit, T = -40°C to +85°C, unless otherwise noted. Typical values are at V = +48V
S
A
S
and T = +25°C.) (Notes 2, 3)
A
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
V
S
Supply Voltage
9
72
V
Measured out of GND, PGOOD or PGOOD
I
Supply Current
1
2
mA
V
GND
open circuit, DRAIN = V
S
V = +36V to +72V
9
8
10
8.5
9
11
S
V
V - V
External Gate Drive
GS
S
GATE
V = +9V
S
V = +36V to +72V
S
5
18
11
| dV
/dt |
Load Voltage Slew Rate
Magnitude
DRAIN
SR
V/ms
C = 10µF
L
V = +9V
S
3
6
V
V increasing
S
Default Undervoltage Lockout
28.5
31.5
34.5
V
V
UVLO
Undervoltage Lockout
Hysteresis
3.5
R
19
32
900
650
1.26
140
150
10
52
kΩ
kΩ
kΩ
V
ON/OFF Pin Input Resistance
ON/OFF
R
DRAIN to GND Resistance
DGND
DRAIN to V Resistance
S
R
DS
V
V
Increasing
1.14
1.38
ON/OFF Reference Threshold
ON/OFF Hysteresis
ON/OFF
ON/OFF
mV
ms
ms
t
Start Delay (Note 4)
80
5
280
18
ON
t
V - V
< 1V
GATE
ON/OFF Off Delay (Note 5)
OFF
S
MAX590_ _AEUT
MAX590_ _BEUT
MAX590_ _CEUT
200
280
400
300
400
500
2
460
540
660
6.5
11
V
V - V
S
Circuit Breaker Threshold
mV
CB
DRAIN
C
C
C
= 1nF
(V - V
) > V
CB
GATE
GATE
GATE
S
DRAIN
until (V - V
< 1V, 200mV
overdrive step
)
S
GATE
= 4.7nF
= 10nF
t
Circuit Breaker Delay (Note 6)
4
µs
CB
7
17
After circuit breaker event,
MAX590_ A_EUT only
t
Restart Delay (Note 4)
80
150
0.3
280
0.6
ms
V
RS
V
I
= 1mA
Power Good Output Low Voltage
OL
OL
2
_______________________________________________________________________________________
+72V SOT23 Simple Swapper Hot-Swap
Controllers
ELECTRICAL CHARACTERISTICS (continued)
(V = +9V to +72V, GND = 0, ON/OFF open circuit, T = -40°C to +85°C, unless otherwise noted. Typical values are at V = +48V
S
A
S
and T = +25°C.) (Notes 2, 3)
A
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
V
V
= 72V (MAX5902)
= 72V (MAX5903)
Power-Good Output Open-Drain
Leakage Current
PGOOD
PGOOD
I
10
µA
OH
T
Thermal Shutdown Temperature
Thermal Shutdown Hysteresis
Junction temperature
+125
15
°C
°C
SD
T
HY
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 T = +25°C, unless otherwise noted. Specifications over -40°C to +85°C are guaran-
A
teed by characterization.
Note 4: This is the delay time from a valid on condition until V begins rising. Valid on conditions are: the device is not in undervolt-
GS
age 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 V falls. Pulses on ON/OFF less than t
are ignored, offering glitch
GS
OFF
immunity.
Note 6: Guaranteed by characterization, not production tested. C
is a capacitor from GATE to V .
S
GATE
Typical Operating Characteristics
(V = +48V, GND = 0, and T = +25°C, unless otherwise noted. See Figure 2 for test circuits.)
S
A
SUPPLY CURRENT
vs. INPUT VOLTAGE
SUPPLY CURRENT
vs. TEMPERATURE
V
THRESHOLD
UVLO
vs. TEMPERATURE
35
34
33
32
31
30
29
28
27
26
25
1.2
1.1
1.0
0.9
0.8
0.7
1.2
1.1
1.0
0.9
0.8
0.7
V
V
= +70V
IN
INCREASING V
IN
IN
= +48V
= +12V
IN
DECREASING V
V
IN
0
15
30
45
60
75
-40
-15
10
35
60
85
-40
-15
10
35
60
85
INPUT VOLTAGE (V)
TEMPERATURE (°C)
TEMPERATURE (°C)
_______________________________________________________________________________________
3
+72V SOT23 Simple Swapper Hot-Swap
Controllers
Typical Operating Characteristics (continued)
(V = +48V, GND = 0, and T = +25°C, unless otherwise noted. See Figure 2 for test circuits.)
S
A
GATE DRIVE VOLTAGE
vs. INPUT VOLTAGE
TURN-ON WAVEFORMS
RETRY TIMEOUT
vs. TEMPERATURE
R = 60Ω, C = 100µF
L
L
MAX5902 toc06
225
200
175
150
125
100
75
15
13
11
9
A
B
C
0
0
0
7
D
0
5
t = 20ms/div
-40
-15
10
35
60
85
0
15
30
45
60
75
A : V , 50V/div
OUT
B : I , 1A/div
TEMPERATURE (°C)
INPUT VOLTAGE (V)
IN
C : V
, 50V/div
GATE
D : V , 50V/div
IN
TURN-ON WAVEFORMS
TURN-ON WAVEFORMS
TURN-ON WAVEFORMS
R = OPEN, C = 100µF
R = 60Ω, C = 10µF
R = 60Ω, C = 100µF
L
L
L
L
L
L
MAX5902 toc08
MAX5902 toc09
MAX5902 toc07
A
B
A
A
0
0
0
0
B
B
0
0
0
C
C
C
0
0
t = 2ms/div
t = 2ms/div
t = 2ms/div
A : V , 50V/div
OUT
A : V , 50V/div
OUT
A : V , 50V/div
OUT
B : I , 0.5A/div
B : I , 1A/div
IN
IN
B : I , 1A/div
IN
C : V
, 20V/div
C : V
, 20V/div
GATE
GATE
C : V
, 20V/div
GATE
CIRCUIT BREAKER EVENT
CIRCUIT BREAKER EVENT
V
= 200mV, C
= 1000pF
GATE
MAX5902 toc11
V
= 20mV, C
= 1000pF
GATE
MAX5902 toc10
OVERDRIVE
OVERDRIVE
0
0
A
A
0
0
0
0
B
B
C
C
t = 1µs/div
t = 1µs/div
A : V , 0.5V/div
DS
A : V , 0.5V/div
DS
B : V , 10V/div
B : V , 10V/div
GS
C : V
GS
C : V
TO V , 50V/div
S
TO V , 50V/div
PGOOD
PGOOD
4
_____________________________S__________________________________________________________
+72V SOT23 Simple Swapper Hot-Swap
Controllers
Pin Description
PIN
NAME
FUNCTION
MAX5902
MAX5903
1
1
V
Positive Supply Voltage Input and External P-Channel MOSFET Source Connection
S
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.
2
2
DRAIN
3
4
3
4
GATE
GND
Gate Drive Output for External P-Channel MOSFET
Ground Connection
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.
—
5
PGOOD
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
ON/OFF
Detailed Description
The MAX5902/MAX5903 are integrated hot-swap con-
troller ICs contained in 6-pin SOT23 packages. They
allow a board to be safely hot-plugged into a live back-
plane 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.
MAX5902
MAX5903
V
S
*
828kΩ
ON/OFF
GND
1kΩ
PGOOD
(PGOOD)
CONTROL
LOGIC
*
34.5kΩ
3V
GND
GND
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 cur-
rent 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
*900kΩ
*650kΩ
DRAIN
( ) ARE FOR THE MAX5903 ONLY
* RELATIVE TOLERANCE 1%, ABSOLUTE TOLERANCE 50% (TYP)
GATE
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
+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 volt-
age across the MOSFET exceeds the circuit breaker
threshold; the supply voltage falls below the undervolt-
age lockout level; the die temperature exceeds
+125°C; or ON/OFF is forced low. After a circuit break-
er fault, the MAX5902L/MAX5903L keep the MOSFET
off until the power is cycled, or the part is reset by tog-
gling 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
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 with-
stand up to +72V.
SCOPE
50kΩ
V
S
GATE DRAIN
SCOPE
V
GATE DRAIN
S
0 TO 0.5V
48V
V
V
IN
MAX5902
ON/OFF
MAX5902A
PGOOD
GND
ON/OFF
PGOOD
GND
I
(a) SUPPLY CURRENT
(d) RETRY TIMEOUT
IRFR5410
SCOPE
SCOPE
SCOPE
SCOPE
V
S
GATE DRAIN
50kΩ
V
GATE
DRAIN
S
R
L
C
L
48V
V
MAX5902
ON/OFF
MAX5902
V
IN
PGOOD
V
GND
ON/OFF
PGOOD
GND
(b) V
(d) STARTUP WAVEFORMS
UVLO
SCOPE
SCOPE
50Ω
V
S
GATE DRAIN
V
GATE
DRAIN
S
V
V
48V
MAX5902
ON/OFF
50kΩ
SCOPE
V
IN
PGOOD
MAX5902
GND
ON/OFF
PGOOD
GND
(b) GATE DRIVE VOLTAGE
(d) CIRCUIT BREAKER EVENT
Figure 2. Test Circuits
_______________________________________________________________________________________
6
+72V SOT23 Simple Swapper Hot-Swap
Controllers
MAX5902N/MAX5903N ignore the MOSFET drain-to-
HOT SWAP CONTROLLER
source voltage for applications where a circuit breaker
+24V
function is not desired.
OPTIONAL
MAX5902
R2
40.2kΩ
MAX5903
Applications Information
ON/OFF
V
S
ON/OFF
GND
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.
R1
3.01kΩ
DGND
GND
Pulling ON/OFF to GND for at least 10ms (t
) forces
OFF
Figure 3. Programmed +18V Lockout, with Optional Optocoupler
On/Off Control.
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, tog-
A thermal shutdown feature protects the external MOS-
FET 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 Appli-
cations section of the data sheet.
gle ON/OFF to GND for at least 10ms (t
).
OFF
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.
A circuit breaker function monitors the voltage across
the external MOSFET, V , and turns off the MOSFET if
SD
V
exceeds the circuit breaker threshold, V . The
SD
CB
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 man-
agement for the MAX5902/MAX5903 is offered with two
different configurations; latched and automatic retry.
HOT SWAP CONTROLLER #1
V
S
Latched Circuit Breaker
After a circuit breaker trip event the latched
versions (MAX5902L/MAX5903L) drive GATE to
MAX5902
MAX5903
V
S
V , turning off the external MOSFET, and PGOOD
S
ON/OFF
GND
(PGOOD) is deasserted. A latched off condition
C
needs to be reset by toggling ON/OFF low for at
least 10ms, or by cycling the power supply, V .
S
Automatic Retry Circuit Breaker
After a circuit breaker trip event the automatic retry
HOT SWAP CONTROLLER #2
versions (MAX5902A/MAX5903A) drive GATE to V ,
S
turning off the external MOSFET, and PGOOD
MAX5902
MAX5903
(PGOOD) is deasserted. If the start conditions are met
V
S
for a full 150ms (t ) the start sequence is re-initiated.
RS
ON/OFF
GND
The start conditions are: the device is not in UVLO;
ON/OFF is not driven low; and the device is not in ther-
mal shutdown.
2C
GND
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
Figure 4. Power-Supply Sequencing
_______________________________________________________________________________________
7
+72V SOT23 Simple Swapper Hot-Swap
Controllers
HOT-SWAP CONTROLLER
HOT-SWAP CONTROLLER
+9V TO +72V
MAX5902
MAX5903
MAX5902
47kΩ
100kΩ
5V LOGIC
GND
ON/OFF
GND
V
S
ON/OFF
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.
GND
Figure 6. Defeating Undervoltage Lockout
Figure 5. Logic Control
and +72V use a resistor divider connected between V
Turn-On and Turn-Off Delays
S
and GND, with the center node of the divider connect-
ed 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:
After power is applied, or ON/OFF is released, there is
a 150ms delay (t ) before the gate ramp is started.
ON
This delay is also the automatic restart time delay.
In the event of a circuit breaker condition or an over-
temperature fault condition, the turn-off delay is less
than 4µs. An undervoltage condition must exist for at
V
UVLO
R2 = R1 ×
− 1
V
ON/OFF
least 10ms (t
) before the MAX5902/MAX5903 turns
OFF
off the external MOSFET. ON/OFF must be held low for
at least 10ms (t ) 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 reset-
ting of the circuit breaker latch (MAX5902L/MAX5903L).
where V
ON/OFF
is the desired lockout voltage, and
UVLO
OFF
V
is the ON/OFF reference threshold specified in
the Electrical Characteristics table (typically 1.26V).
Figure 3 shows an example circuit with V
set for
UVLO
+18V. To defeat the UVLO simply connect a single
100kΩ resistor between ON/OFF and V , as shown in
S
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 MOS-
FET. 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.
Figure 6.
The Power Good Output
The power good output, PGOOD (PGOOD), is open-
drain and asserts when the external MOSFET is fully
enhanced and V
is less than the circuit breaker
SD
threshold (V ). For versions without the circuit breaker
CB
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 V < V
for
S
UVLO
longer than 10ms or ON/OFF is held low for longer than
Undervoltage Lockout
The MAX5902/MAX5903 turns off the external MOSFET
if the magnitude of the input voltage is below the level
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.
set by ON/OFF for longer than 10ms (t
). If ON/OFF
OFF
is left unconnected, the lockout voltage (V
)
UVLO
defaults to 31.5V. V
may also be set to any value
UVLO
within the power-supply range by using external resis-
tors. To set the lockout voltage to a value between +9V
8
_______________________________________________________________________________________
+72V SOT23 Simple Swapper Hot-Swap
Controllers
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
GROUND
U1
SOT23-6
MAX5902/MAX5903
flows through the external MOSFET, a voltage, V , is
SD
generated from source to drain due to the MOSFET’s
POWER IN
on-resistance, R
. The MAX5902A/MAX5903A
DS(ON)
S
D G
M1
SOT-223
and MAX5902L/MAX5903L monitor V when the exter-
POWER
OUT
SD
nal MOSFET is fully enhanced. If V
exceeds the cir-
SD
cuit breaker threshold the external MOSFET is turned
off, and PGOOD (PGOOD) is deasserted. To accom-
modate different MOSFETs and different load currents
the MAX5902/MAX5903 are available with circuit break-
er threshold voltages of 300mV, 400mV, and 500mV. To
determine the proper circuit breaker threshold for an
application use:
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 con-
trolling the load voltage slew rate, but inrush current is
also a function of load capacitance. Determine inrush
current using:
V
CB
> (R
) ✕ (I )
OUT(MAX)
DS(ON)
where R
OUT
is the on-resistance of the MOSFET and
DS(ON)
I
(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.
dV
dt
I = C
= C × SR
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 dis-
abling the external MOSFET. For calculating the circuit
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 cur-
rent is 0.9A typical.
breaker threshold use the MOSFET’s R
at the worst
ON
possible operating condition, and add a 20% overcur-
rent margin to the maximum circuit current. For
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.
instance, if a MOSFET has an R
of 0.06Ω at T
=
A
ON
+25°C, and a normalized on-resistance factor of 1.75 at
= +130°C (from the MOSFET data sheet), the R
T
A
ON
used for calculation is the product of these two num-
bers, or (0.06Ω) x (1.75) = 0.105Ω. Then, if the maxi-
mum 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.
Suggested External MOSFETs
SUGGESTED
EXTERNAL
MOSFET
MAXIMUM
SUGGESTED MAXIM
PART
I
(A)
LOAD
0.5
1
IRF9540NS
IRF9540NS
IRF5210S
IRF5210S
MAX5902AAEUT
MAX5902ABEUT
MAX5902ABEUT
MAX5902ACEUT
2
3
V
IN
= +9V to +72V
_______________________________________________________________________________________
9
+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
POWER GOOD
OUTPUT LOGIC
PART
TOP MARK
THRESHOLD
AASM
AASA
AASB
AASC
AASD
AASE
AASF
AASN
AASG
AASH
AASI
MAX5902NNEUT*†
MAX5902AAEUT*†
MAX5902ABEUT*
MAX5902ACEUT*†
MAX5902LAEUT*†
MAX5902LBEUT*†
MAX5902LCEUT*
MAX5903NNEUT*†
MAX5903AAEUT*
MAX5903ABEUT*†
MAX5903ACEUT*†
MAX5903LAEUT*†
MAX5903LBEUT*†
MAX5903LCEUT*†
None
None
300mV
400mV
500mV
300mV
400mV
500mV
None
Active-Low
Active-Low
Active-Low
Active-Low
Active-Low
Active-Low
Active-Low
Active-High
Active-High
Active-High
Active-High
Active-High
Active-High
Active-High
Auto Retry
Auto Retry
Auto Retry
Latched
Latched
Latched
None
Auto Retry
Auto Retry
Auto Retry
Latched
Latched
Latched
300mV
400mV
500mV
300mV
400mV
500mV
AASJ
AASK
AASL
*Requires special solder temperature profile described in the Absolute Maximum Ratings section.
†Future products—contact factory for availability.
Typical Operating Circuits (continued)
50W ISOLATED
POWER SUPPLY
BACKPLANE CIRCUIT CARD
+48V
IRFR5410
HOT SWAP CONTROLLER
V+
1MΩ
MAX5903
MAX5003*
V
S
GATE
INDIV
ON/OFF
GND
DRAIN
39kΩ
PGOOD
GND
GND
*THE MAX5003 IS A 110V PWM CONTROLLER
10 ______________________________________________________________________________________
+72V SOT23 Simple Swapper Hot-Swap
Controllers
Package Information
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
© 2001 Maxim Integrated Products
Printed USA
is a registered trademark of Maxim Integrated Products.
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