UC3903

· Inputs for Monitoring up to Four Separate Supply Voltage Levels
· Internal Inverter for Sensing a Negative Supply Voltage
· Line/Switch Sense Input for Early Power Source Failure Warning
· Programmable Under- and Over-Voltage Fault Thresholds with Proportional Hysteresis
· A Precision 2.5V Reference
· General Purpose Op-Amp for Auxiliary Use
· Three High Current, >30mA, Open-Collector Outputs Indicate Over-Voltage, Under-Voltage and Power OK Conditions
· Input Supply Under-Voltage Sensing and Start-Latch Eliminate Erroneous Fault Alerts During Start-Up
· 8-40V Supply Operation with 7mA Stand-By Current

Supply Voltage (+V_IN). . . . . . . . . . . . . . . . . . . . . . . . . .. . . +40V
Open Collector Output Voltages. . . . . . . . . . . . . . . . . . .. . +40V
Open Collector Output Currents. . . . . . . . . . . . . . . . . . . . 50mA
Sense 1-4 Input Voltages . . . . . . . . . . . . . . . . . . -0.3V to +20V
Line/Switcher Sense Input Voltage . . . . . . . .  . .  -0.3V to +40V
Op-Amp and Inverter Input Voltages . . . . . . . .. . -0.3V to +40V
Op-Amp and Inverter Output Currents . . . . . . . . . . . . . . -40mA
Window Adjust Voltage. . . . . . . . . . . . . . . . . . . .. 0.0V to +10V
Delay Pin Voltages . . . . . . . . . . . . . . . . . . . . . . . . . 0.0V to +5V
Reference Output Current . . . . . . . . . . . . . . . . . . . .  . . . -40mA
Power Dissipation at T_A = 25°C (Note 1) . . . . . . . . . . .1000mW
Power Dissipation at T_C = 25°C (Note 1) . . . . . . . . . . 2000mW
Operating Junction Temperature . . . . . . . . . . . -5°C to +150°C
Storage Temperature . . . . . . . . . . . . . . . . . . .. -5°C to +150°C
Lead Temperature (Soldering, 10 Seconds) . . . . . . . . .  .300°C

The UC3903 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 of UC3903  is available to provide early warning of line or other power source failures.

The fault window adjustment circuit of UC3903 on these devices provides easy programming of under- and over-voltage thresholds. The thresholds, centered around a precision 2.5V reference, have an input hysteresis that scales with the window width for precise, glitch-free operation. A reference output pin of UC3903 allows the sense input fault windows to be scaled independently using simple resistive dividers.

The three open collector outputs of UC3903 on these devices will sink in excess of 30mA 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 UC3903 is also included. This op-amp, capable of sourcing 20mA of output current, can be used for a number of auxiliary functions including the sensing and amplification of a feedback error signal when the 2.5V output is used as a system reference.

In addition, these ICs UC3903 are equipped with a start-latch to prevent erroneous under- 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.