LT4256-1/LT4256-2

1

425612f

APPLICATIO S

FEATURES

TYPICAL APPLICATIO

DESCRIPTIO

The LT

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

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.

s

Hot Board Insertion

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Electronic Circuit Breaker/Power Bussing

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Industrial High Side Switch/Circuit Breaker

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24V/48V Industrial/Alarm Systems

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Ideally Suited for 12V, 24V and 48V Distributed

Power Systems

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48V Telecom Systems

, LTC and LT are registered trademarks of Linear Technology Corporation.

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Allows Safe Board Insertion and Removal from a

Live Backplane

s

Controls Supply Voltage from 10.8V to 80V

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Foldback Current Limiting

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Overcurrent Fault Detection

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Drives an External N-Channel MOSFET

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Programmable Supply Voltage Power-Up Rate

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Undervoltage Protection

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Latch Off Operation Mode (LT4256-1)

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Automatic Retry (LT4256-2)

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Available in an 8-Pin SO Package

Positive High Voltage

Hot Swap Controllers

Hot Swap is a trademark of Linear Technology Corporation.

4256 TA01

0.02

Ω

LT4256-1/

LT4256-2

SENSE

6

2

3

4

87

1

5

GATE

FB

PWRGD

UV

TIMER

GND

48V

GND

(SHORT PIN)

IRF530

CMPZ5241B

11V

8.06k

64.9k

100

Ω

4.02k

10

Ω

36.5k

PWRGD

48V

2A

27k

33nF

0.1

µF

10nF

SMAT70A

UV = 36V

PWRGD = 40V

48V, 2A Hot Swap Controller

PWRGD

50V/DIV

50V/DIV

INRUSH

CURRENT

500mA/DIV

50V/DIV

2.5ms/DIV

4256 TA02

LT4256 Start-Up Behavior