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SC4250

Negative Voltage

Hot Swap Controller

POWER MANAGEMENT

Revision: April 6, 2005

Programmable slew of the inrush current when

used for hot insertion in the negative 24V and 48V

backplane

Closed loop operation limits the maximum current

even in short circuit condition

Built in timer prevents false shutdown when the

closed loop operation limits the current

Sensing the drain voltage allows for immediate

shutdown in short circuit conditions where current

spikes and noise are ignored

Power good signal

Input UVLO and OVLO sensing

Circuit breaker and retry

SO-8 package

Central office switching

-48V Distributed power systems

Power supply hotswap & inrush control

Description

Features

Applications

Typical Application Circuit

The SC4250 is a negative voltage hotswap controller

that allows the insertion of line cards into a live backplane.

The inrush current is programmable, and the closed loop

operation limits the maximum current even under short

circuit conditions. A built-in timing circuit prevents false

shutdown. The signal from the drain voltage is fed to the

timer, providing safety for the MOSFET when in linear

mode. The SC4250 latches off under abnormal condi-

tions The power has to be recycled in order to resume

operation.

The device comes in two options, PWRGD (SC4250H)

and PWRGD (SC4250L). These high or low signals can

be directly used to enable power modules.

Figure 1

Q1

C3

0.33

C5

150

GND

-- 48V

R5

10

R1

562k

R3

10.2k

R4

0.01

R6

18k

R2

9.31k

C4

3.3nF

DRAIN

7

UV

3

VEE

4

GATE

6

PWRGD

1

SENSE

5

VCC

8

OV

2

U1

SC4250

GND(remote)

C2

0.001

C1

0.1

Vee

PWRGD/PWRGD

/PWRGD

VEE