Product details

Number of supplies monitored 1 Threshold voltage 1 (Typ) (V) 2.5 Features Overcurrent sense, Overvoltage sense Reset threshold accuracy (%) 1 Output driver type/reset output Active-low, Open-drain Time delay (ms) Programmable Rating Catalog Watchdog timer WDI (sec) None Operating temperature range (C) -40 to 85
Number of supplies monitored 1 Threshold voltage 1 (Typ) (V) 2.5 Features Overcurrent sense, Overvoltage sense Reset threshold accuracy (%) 1 Output driver type/reset output Active-low, Open-drain Time delay (ms) Programmable Rating Catalog Watchdog timer WDI (sec) None Operating temperature range (C) -40 to 85
SOIC (DW) 16 77 mm² 10.3 x 7.5
  • Includes Over-Voltage, Under-Voltage, and Current Sensing Circuits
  • Internal 1% Accurate Reference
  • Programmable Time Delays
  • SCR "Crowbar" Drive of 300 mA
  • Remote Activation Capability
  • Optional Over-Voltage Latch
  • Uncommitted Comparator Inputs for Low Voltage Sensing (UC1544 Series Only)

  • Includes Over-Voltage, Under-Voltage, and Current Sensing Circuits
  • Internal 1% Accurate Reference
  • Programmable Time Delays
  • SCR "Crowbar" Drive of 300 mA
  • Remote Activation Capability
  • Optional Over-Voltage Latch
  • Uncommitted Comparator Inputs for Low Voltage Sensing (UC1544 Series Only)

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 undervoltage (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 device, together with an independent, accurate reference generator.

Both over- and under-voltage sensing circuits can be externally programmed for minimum time duration of fault before triggering. All functions contain open collector 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.

The UC1544/2544/3544 devices have the added versatility of completely uncommitted inputs to the voltage sensing comparators so that levels less than 2.5 V 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 highgain 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.

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 undervoltage (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 device, together with an independent, accurate reference generator.

Both over- and under-voltage sensing circuits can be externally programmed for minimum time duration of fault before triggering. All functions contain open collector 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.

The UC1544/2544/3544 devices have the added versatility of completely uncommitted inputs to the voltage sensing comparators so that levels less than 2.5 V 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 highgain 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.

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Type Title Date
* Data sheet Power Supply Supervisory Circuit datasheet (Rev. A) 08 Feb 2007
Technical article 3 quiescent-current (Iq) specifications you need to understand 12 Nov 2021
Application note Optimizing Resistor Dividers at a Comparator (Rev. B) 30 Apr 2021
Technical article Monitoring 12-V automotive battery systems: Load-dump, cold-crank and false-reset management 24 Mar 2021
E-book Voltage Supervisor and Reset ICs: Tips, Tricks and Basics 28 Jun 2019
Application note Choosing an Appropriate Pull-up/Pull-down Resistor for Open Drain Outputs 19 Sep 2011

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