UC1903
UC2903
UC3903
Quad Supply and Line Monitor
FEATURES
DESCRIPTION
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Inputs for Monitoring up to Four
Separate Supply Voltage Levels
The UC1903 family of quad supply and line monitor integrated circuits will re-
spond to under- and over-voltage conditions on up to four continuously moni-
tored voltage levels. An internal op-amp inverter allows at least one of these
levels to be negative. A separate line/switcher sense input is available to pro-
vide early warning of line or other power source failures.
Internal Inverter for Sensing a
Negative Supply Voltage
Line/Switch Sense Input for Early
Power Source Failure Warning
The fault window adjustment circuit on these devices provides easy program-
ming of under- and over-voltage thresholds. The thresholds, centered around
a precision 2.5V reference, have an input hysteresis that scales with the win-
dow width for precise, glitch-free operation. A reference output pin allows the
sense input fault windows to be scaled independently using simple resistive
dividers.
Programmable Under- and
Over-Voltage Fault Thresholds
with Proportional Hysteresis
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A Precision 2.5V Reference
The three open collector outputs on these devices will sink in excess of 30mA
of load current when active. The under- and over-voltage outputs respond af-
ter separate, user defined, delays to respective fault conditions. The third out-
put is active during any fault condition including under- and over-voltage,
line/switcher faults, and input supply under-voltage. The off state of this out-
put indicates a "power OK" situation.
General Purpose Op-Amp for
Auxiliary Use
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Three High Current, >30mA,
Open-Collector Outputs Indicate
Over-Voltage, Under-Voltage
and Power OK Conditions
An additional, uncommitted, general purpose op-amp is also included. This
op-amp, capable of sourcing 20mA of output current, can be used for a num-
ber of auxiliary functions including the sensing and amplification of a feed-
back error signal when the 2.5V output is used as a system reference.
Input Supply Under-Voltage
Sensing and Start-Latch
Eliminate Erroneous Fault Alerts
During Start-Up
In addition, these ICs are equipped with a start-latch to prevent erroneous un-
der-voltage indications during start-up. These parts operate over an 8V to
40V input supply range and require a typical stand-by current of only 7mA.
8-40V Supply Operation with
7mA Stand-By Current
BLOCK DIAGRAM
Note: Pin numbers refer to J, N and DW packages.
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