Rev 1.1a 3.19.2005

Microsemi Inc.

Copyright

© 1994

11861 Western Avenue

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∞

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∞ Garden Grove, CA 92841

1

(714) 898-8121

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∞ FAX: (714) 893-2570

LOW-VOLTAGE SUPERVISORY CIRCUIT

FEATURES

••••• Uncommitted comparator inputs for

wide input flexibility

••••• Common-Mode range from zero to near

supply voltage

••••• Reference voltage trimmed to 1%

accuracy

••••• Over-voltage, under-voltage, and current

sensing circuits all included

••••• SCR "Crowbar" drive of 300mA

••••• Programmable time delays

••••• Open-collector outputs and remote

activation capability

••••• Total standby current less than 10mA

HIGH RELIABILITY FEATURES

- SG1544

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♦ Available to MIL-STD-883 and DESC

SMD

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♦ LMI level "S" processing available

DESCRIPTION

This device was designed to provide all the operational features of the SG1543/

2543/3543 devices but with the added advantage of uncommitted inputs to the

voltage sensing comparators. This allows monitoring of voltage levels less than

2.5 volts by dividing down the internal reference supply.

In all other respects, the SG1544 series is identical to the SG1543 series. These

monolithic devices contain all the functions necessary to monitor and control the

output of a sophisticated power supply system.

Over-voltage sensing with

provision to trigger an external SCR “crowbar” shutdown; an under-voltage circuit

which can be used to monitor either the output or sample the input line voltage;

and a third op amp/comparator usable for current sensing are all included in this

IC, together with an independent, accurate reference generator.

The voltage-sensing input comparators are identical and can be used with

threshold levels from zero volts to (V

Each has approximately 25mv of

hysteresis which is offset so the switching differential threshold is zero on the non-

inverting input for rising levels and zero on the inverting input for falling signals.

All other operating characteristics are as described in the SG1543 data sheet and

application note.

BLOCK DIAGRAM

SG1544/SG2544/SG3544