MAX4272ESA Maxim Integrated Products, MAX4272ESA Datasheet - Page 21

• Manufacturer Part Number: MAX4272ESA
• Description: Hot Swap & Power Distribution
• Manufacturer: Maxim Integrated Products

Specifications of MAX4272ESA

• Lead Free Status / Rohs Status: Lead free / RoHS Compliant

is discharged immediately, but note that the MOSFET is
not completely off until V
power supply collapses below UVLO, the MAX4271/
MAX4272/MAX4273 will force the device to restart in
startup mode with a 150ms delay once the supply has
recovered. The main system power supply must be
able to deliver this fault current without excessive volt-
age drop.
The MOSFET is turned off in a very short time; there-
fore, the resulting dv/dt can be considerable. The back-
plane delivering the power to the external card must
have a fairly low inductance to limit the voltage tran-
sients caused by the removal of a fault. Bypassing the
input with a small capacitor alleviates false UVLO trips
due to these transients.
During normal operation, the MOSFET dissipates little
power, it is fully turned on, and its R
The power dissipated in normal operation is P
I
dissipated during the startup and turn-off transients.
The design must take into consideration the worst-case
scenario of a continuous short-circuit fault present on
the board. Two cases need to be considered:
1) The single turn-on with the device latched after a
2) The continuous automatic retry (when using the
Use the following equation to calculate the maximum
transient thermal resistance (in °C/W) required for an
output short to ground:
Figure 15. Adjustable Undervoltage Lockout and Output Voltage Reset Generator
with Autoretry, DualSpeed/BiLevel Fault Protection
LOAD
fault (when using MAX4271 or MAX4273 in latched
mode)
MAX4272 or MAX4273 in retry mode)
Z
2
3V to 12V Current-Limiting Hot-Swap Controllers
θJA
x R
(max) = (T
DS(ON)
MOSFET Thermal Considerations
. A considerable amount of power is
______________________________________________________________________________________
JMAX
GS
- T
< V
A
) / (V
TH
•
•
•
. If the main system
IN
DS(ON)
✕
•
•
•
I
FAST, SET
V
IN
is minimal.
ON
IN
)
D
MAX4273
=
SENSE
MOSFET manufacturers typically include curves for the
transient thermal resistance, Z
(Figure 17). Find the thermal impedance of the MOS-
FET by using t
choosing the single pulse curve for latched mode parts
or by choosing the duty cycle = 0.03 curve for the
MAX4272 (the duty cycle is fixed at 32:1). If the Z
required is less than that of the package, reduce
t
FET, or choose one with better thermal characteristics.
Figure 16. Using the MAX4271/MAX4272/MAX4273 on a
Backplane
START
V
IN
LLMON
GATE
OUTC
INC
, reduce I
IN
CTIM
MAX4271
MAX4272
MAX4273
START
SENSE
FAST,SET
GATE
ON
100k
as the pulse duration and by
RESET
, use a heatsink on the MOS-
μP
BACKPLANE
θJA
REMOVABLE CARD
WITH NO HOT-INSERTION
PROTECTION
, of the package
C
BOARD
V
OUT
θJA
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