LT4254
Positive High Voltage
Hot Swap Controller
with Open-Circuit Detect
FEATURES
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DESCRIPTIO
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Allows Safe Board Insertion and Removal from a
Live Backplane
Controls Supply Voltage from 10.8V to 36V
Foldback Current Limiting
Open Circuit and Overcurrent Fault Detect
Drives an External N-Channel MOSFET
Automatic Retry or Latched Off Operation
After Overcurrent Fault
Programmable Supply Voltage Power-Up Rate
Undervoltage and Overvoltage Protection
Open MOSFET Detection
The LT
®
4254 is a high voltage Hot Swap controller that
allows a board to be safely inserted and removed from a
live backplane. An internal driver controls the high side
N-channel MOSFET gate for supply voltages ranging from
10.8V to 36V. The part features an open-circuit detect
(OPEN) output that indicates abnormally low load current
conditions.
The LT4254 features an adjustable analog foldback cur-
rent limit. If the supply remains in current limit for more
than a programmable time, the N-channel MOSFET shuts
off, the PWRGD output goes low and the LT4254 either
automatically restarts after a time-out delay or latches off
until the UV pin is cycled low. The RETRY pin sets whether
the part will automatically restart after an overcurrent fault
or if it will latch off until the UV pin is cycled low.
The PWRGD output indicates when the output voltage
rises above a programmed level. An external resistor
string from V
CC
provides programmable undervoltage and
overvoltage protection.
The LT4254 is available in a 16-lead SSOP package.
, LTC and LT are registered trademarks of Linear Technology Corporation.
Hot Swap is a trademark of Linear Technology Corporation.
APPLICATIO S
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Hot Board Insertion
Electronic Circuit Breaker/Power Bussing
Industrial High Side Switch/Circuit Breaker
24V Industrial/Alarm Systems
12V and 24V Distributed Power Systems
TYPICAL APPLICATIO
V
IN
24V
(SHORT PIN)
16
R1
324k
1
UV
LT4254
2
4
10
GND
C2
33nF
V
CC
15
SENSE
R5
0.025Ω
24V, 2A Hot Swap Controller
Q1
IRF530
D1
CMPZ5241B
11V
13
R6
10Ω
R7
100Ω
C1
10nF
R9
40.2k
PWRGD
UV = 20V
OV = 40V
PWRGD = 18V
4254 TA01
C
L
R8
140k
R4
27k
V
OUT
24V
1.5A
PWRGD
20V/DIV
GATE
V
CC
20V/DIV
C3
0.1µF
R2
40.2k
R3
40.2k
OV
OPEN
TIMER
FB
RETRY
PWRGD
GND
8
10
7
5
V
OUT
20V/DIV
GATE
20V/DIV
2.5ms/DIV
4245 TA02
U
TM
U
U
LT4254 Start-Up Behavior
CONTACT BOUNCE
4254f
1
LINER [ LINEAR TECHNOLOGY ]
