LT4256-1_15 Datasheet, PDF (1/16 Pages) Linear Technology – Positive High Voltage Hot Swap Controllers

LT4256-1/LT4256-2
Positive High Voltage
Hot Swap Controllers
FEATURES
■ _{Allows Safe Board Insertion and Removal from a}
Live Backplane
■ _{Controls Supply Voltage from 10.8V to 80V}
■ _{Foldback Current Limiting}
■ _{Overcurrent Fault Detection}
■ _{Drives an External N-Channel MOSFET}
■ _{Programmable Supply Voltage Power-Up Rate}
■ _{Undervoltage Protection}
■ _{Latch Off Operation Mode (LT4256-1)}
■ _{Automatic Retry (LT4256-2)}
■ _{Available in an 8-Pin SO Package}
U
APPLICATIO S
■ _{Hot Board Insertion}
■ _{Electronic Circuit Breaker/Power Bussing}
■ _{Industrial High Side Switch/Circuit Breaker}
■ _{24V/48V Industrial/Alarm Systems}
■ _{Ideally Suited for 12V, 24V and 48V Distributed}
Power Systems
■ _{48V Telecom Systems}
DESCRIPTIO
The LT^®4256-1/LT4256-2 are high voltage Hot Swap^TM
controllers that allow a board to be safely inserted and
removed from a live backplane. An internal driver drives an
external N-channel MOSFET switch to control supply
voltages ranging from 10.8V to 80V.
The LT4256-1/LT4256-2 features an adjustable analog
foldback current limit. If the supply remains in current limit
for more than a programmable time, the N-channel
MOSFET shuts off and the PWRGD output asserts low. The
LT4256-2 automatically restarts after a time-out delay.
The LT4256-1 latches 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
protection.
The LT4256 can be used as an upgrade to LT1641 designs.
See Table 1 on page 14 for upgraded specifications.
The LT4256-1 and LT4256-2 are available in an 8-pin SO
package that is pin compatible with the LT1641.
, 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
48V, 2A Hot Swap Controller
V_IN
0.02Ω
IRF530
48V
SMAT70A
CMPZ5241B
(SHORT PIN)
11V
8
7
64.9k
V_CC
1
UV
SENSE ^10Ω
6
GATE
10nF
100Ω
36.5k
0.1µF
8.06k
LT4256-1/
LT4256-2
2
FB
4.02k
V_OUT
48V
C_L ^2A
27k
V_IN
50V/DIV
V_OUT
50V/DIV
INRUSH
CURRENT
500mA/DIV
LT4256 Start-Up Behavior
5
TIMER
3
PWRGD
UV = 36V
PWRGD
4256 TA01
PWRGD _{CL = 225µF}
50V/DIV
2.5ms/DIV
4256 TA02
GND
33nF
GND
PWRGD = 40V
4
425612fa
1