The UC1903 family of quad supply and line monitor integrated circuits will respond
to under- and over-voltage conditions on up to four continuously monitored
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 provide
early warning of line or other power source failures.
The fault window adjustment circuit on these devices provides easy programming
of under- and over-voltage thresholds. The thresholds, centered around
a precision 2.5-V reference, have an input hysteresis that scales with the window
width for precise, glitch-free operation. A reference output pin allows the
sense input fault windows to be scaled independently using simple resistive
The three open collector outputs on these devices sink in excess of 30 mA
of load current when active. The under- and over-voltage outputs respond after
separate, user defined, delays to respective fault conditions. The third output
is active during any fault condition including under- and over-voltage,
line/switcher faults, and input supply under-voltage. The off state of this output
indicates a "power OK" situation.
An additional, uncommitted, general purpose op-amp is also included. This
op-amp, capable of sourcing 20 mA of output current, can be used for a number
of auxiliary functions including the sensing and amplification of a feedback
error signal when the 2.5-V output is used as a system reference.
These parts operate over an 8-V to
40-V input supply range and require a typical stand-by current of only 7 mA.