SG1543/SG2543/SG3543

11/91 Rev 1.1 2/94

Copyright

© 1994

11861 Western Avenue

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∞ Garden Grove, CA 92841

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(714) 898-8121

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∞ FAX: (714) 893-2570

POWER SUPPLY OUTPUT SUPERVISORY CIRCUIT

FEATURES

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

current sensing circuits all

included

••••• Reference voltage trimmed to 1%

accuracy

••••• SCR "Crowbar" drive of 300mA

••••• Programmable time delays

••••• Open-collector outputs and

remote activation capability

••••• Total standby current less than

10mA

HIGH RELIABILITY FEATURES

- SG1543

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♦ Available to MIL-STD-883 and

DESC SMD

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♦ LMI level "S" processing avail-

able

DESCRIPTION

This monolithic integrated circuit contains all the functions necessary to monitor and

control the output of a sophisticated power supply system. Over-voltage (O.V.) sensing

with provision to trigger an external SCR “crowbar” shutdown; an under-voltage (U.V.)

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

and a third op amp/comparator usable for current sensing (C.L.) are all included in this

IC, together with an independent, accurate reference generator.

Both over and under-voltage sensing circuits can be externally programmed for mini-

mum time duration of fault before triggering. All functions contain open collector outputs

which can be used independently or wire-ORed together; and although the SCR trigger

is directly connected only to the over-voltage sensing circuit, it may be optionally

activated by any of the other outputs, or from an external signal. The O.V. circuit also

includes an optional latch and external reset capability.

The current sense circuit may be used with external compensation as a linear amplifier

or as a high gain comparator. Although nominally set for zero input offset, a fixed

threshold may be added with an external resistor. Instead of current limiting, this circuit

may also be used as an additional voltage monitor.

The reference generator circuit is internally trimmed to eliminate the need for external

potentiometers and the entire circuit may be powered directly from either the output being

monitored or from a separate bias voltage.

BLOCK DIAGRAM