1

4251b12f

LTC4251B/LTC4251B-1/

LTC4251B-2

+

LTC4251B

UV/OV

TIMER

GATE

SENSE

LOAD

–48RTN

–48RTN

(SHORT PIN)

†

DDZ13B**

R1

402k

1%

10Ω

0.02Ω

R2

32.4k

1%

–48V

150nF

C1

10nF

18nF

1μF

100μF

10k

500mW

Q1

IRF530S

4251b12 TA01a

4

3

2

1

*TWO 0.25W RESISTORS IN SERIES FOR

**DIODES, INC.

†RECOMMENDED FOR HARSH ENVIRONMENTS

GATE

5V/DIV

SENSE

2.5A/DIV

20V/DIV

4251b12 TA01b

1ms/DIV

TYPICAL APPLICATION

FEATURES

DESCRIPTION

Negative Voltage

Hot Swap Controllers in SOT-23

APPLICATIONS

L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks and

Hot Swap and ThinSOT are trademarks of Linear Technology Corporation. All other trademarks

are the property of their respective owners.

Live –48V Backplane

Operation

Breaker Timer

Hot Swap™ controllers allow a board to be safely inserted

and removed from a live backplane. Output current is con-

trolled by three stages of current limiting: a timed circuit

breaker, active current limiting and a fast feedforward path

that limits peak current under worst-case catastrophic

fault conditions.

Programmable undervoltage and overvoltage detectors

disconnect the load whenever the input supply exceeds

the desired operating range. The supply input is shunt

regulated, allowing safe operation with very high supply

voltages. A multifunction timer delays initial start-up and

controls the circuit breaker’s response time.

The LTC4251B UV/OV thresholds are designed to match

the standard telecom operating range of – 43V to –75V. The

LTC4251B-1 UV/OV thresholds extend the operating range

to encompass –36V to –72V. The LTC4251B-2 implements

a UV threshold of –43V only. The LTC4251B improves the

ruggedness of the LTC4251 shunt regulator.

–48V, 2.5A Hot Swap Controller

Start-Up Behavior