LT4254_15 Datasheet, PDF (1/16 Pages) Linear Technology – Positive High Voltage Hot Swap Controller with Open-Circuit Detect

FEATURES
■ _{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}
■ _{Available in 16-Lead SSOP Package}
U
APPLICATIO S
■ _{Hot Board Insertion}
■ _{Electronic Circuit Breaker/Power Bussing}
■ _{Industrial High Side Switch/Circuit Breaker}
■ _{24V Industrial/Alarm Systems}
■ _{12V and 24V Distributed Power Systems}
LT4254
Positive High Voltage
Hot Swap Controller
with Open-Circuit Detect
DESCRIPTIO
The LT^®4254 is a high voltage Hot Swap^TM 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.
, LTC and LT are registered trademarks of Linear Technology Corporation.
Hot Swap is a trademark of Linear Technology Corporation.
All other trademarks are the property of their respective owners.
TYPICAL APPLICATIO
24V, 2A Hot Swap Controller
V_IN
24V
(SHORT PIN)
R1
324k
C3
0.1µF
R2
40.2k
R3
40.2k
R5
0.025Ω
V_CC SENSE
UV
GATE
LT4254
OV
OPEN
FB
RETRY
Q1
IRF530
R6
10Ω
D1
CMPZ5241B
11V
R8
140k
V_OUT
24V
C_L ^1.5A
R7
R4
100Ω
27k
C1
10nF
R9
40.2k
TIMER PWRGD
PWRGD
GND
C2
GND
33nF
UV = 20V
4254 TA01
OV = 40V
PWRGD = 18V
LT4254 Start-Up Behavior
V_IN
20V/DIV
V_OUT
20V/DIV
CONTACT BOUNCE
INRUSH
CURRENT
500mA/DIV
PWRGD
20V/DIV
C_L = 168µF
2.5ms/DIV
4245 TA02
4254fb
1