1

LTC1921

1921i

Dual –48V Supply

and Fuse Monitor

May 2002

The LTC

including their fuses, and drives up to three optoisolators

to indicate status, in accordance with standard backplane

specifications. Requiring only three noncritical resistors

and optoisolators, the LTC1921 replaces multiple voltage

comparators, a voltage reference and several precision

resistors.

The monitor features dual supply overvoltage and under-

voltage detection circuits. The preset trip thresholds in-

clude overvoltage, undervoltage and undervoltage recovery

that are guaranteed over temperature and meet or exceed

common backplane specifications. Additional built-in cir-

cuitry detects the condition of supply fuses. Overvoltage

and undervoltage detectors ignore fast supply transients,

eliminating false detection. The LTC1921 operates from

–10V to –80V with a typical power dissipation of less than

10mW.

The LTC1921 is available in an 8-pin MSOP package.

s

Independently Monitors Two –48V Supplies for

– Undervoltage Faults: –38.5V

– Overvoltage Faults: –70V

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Accurately Detects Undervoltage Fault Recovery:

–43V

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Monitors Two External Fuses

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Operates from –10V to –80V

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Tolerates DC Faults to –100V

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Tolerates Accidental Supply Reversal to 100V

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Withstands Transient Voltages Up to 200V/–200V

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Small Footprint: 8-Lead MSOP Package

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Requires No Precision External Components

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Specified from – 40

°C to 85°C

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Telecom Backplanes or Switch Cards

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Networking Backplanes or Switch Cards

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High Voltage Fuse Monitoring

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

Information furnished by Linear Technology Corporation is believed to be accurate and reliable.

However, no responsibility is assumed for its use. Linear Technology Corporation makes no represen-

tation that the interconnection of its circuits as described herein will not infringe on existing patent rights.

FUSE GOOD

SUPPLY A GOOD

MOC207

MOC207

MOC207

1921 TA01

SUPERVISOR

µP

LOGIC

SUPPLY

LOGIC

COMMON

47k

47k

47k

R3

47k

1/4W

SUPPLY B GOOD

OUT F

3

4

5

7

2

8

1

6

FUSE A

RTN

LTC1921

FUSE B

OUT A

OUT B

D1 MURS320

F1

SUPPLY A

–48V

SUPPLY B

–48V

F2

D2 MURS320

R1

100k

– 48V

RETURN

R2

100k

–48V LOAD

Final Electrical Specifications

FEATURES

DESCRIPTIO

APPLICATIO S

TYPICAL APPLICATIO