UC1543 UC1544
UC2543 UC2544
UC3543 UC3544
Power Supply Supervisory Circuit
FEATURES
DESCRIPTION
•
Includes Over-voltage,
The monolithic integrated circuits contain 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.
Under-voltage, And Current
Sensing Circuits
•
Internal 1% Accurate
Reference
•
•
Programmable Time Delays
SCR “Crowbar” Drive Of
300mA
Both over- and under-voltage sensing circuits can be externally programmed for
minimum time duration of fault before triggering. All functions contain open collec-
tor outputs which can be used independently or wire-or’ed 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.
•
•
•
Remote Activation Capability
Optional Over-voltage Latch
Uncommitted Comparator
Inputs For Low Voltage
Sensing (UC1544 Series
Only)
The UC1544/2544/3544 devices have the added versatility of completely uncom-
mitted inputs to the voltage sensing comparators so that levels less than 2.5V may
be monitored by dividing down the internal reference voltage. 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 ex-
ternal potentiometers and the entire circuit may be powered directly from either the
output being monitored or from a separate bias voltage.
BLOCK DIAGRAM
Note: For each terminal, first number refers to 1543 series, second to 1544 series.
* On 1543 series, this function is internally connected to VREF.
4/97
Powered by ICminer.com Electronic-Library Service CopyRight 2003