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Microcontroller Supervisory IC Application Note

Technical Notes

Voltage Detector & Watchdog Timer

When connecting a resistor (R1) to an input of this device, the input voltage decreases by [Device’s Consumption Current] x [Resistance Value] only. And, the cross conduction current*1, which occurs when changing from the detecting state to the release state, is decreased the input voltage by [Cross Conduction Current] x [Resistance Value] only. And then, this device will enter the re-detecting state if the input voltage reduction is larger than the difference between the detector voltage and the released voltage.
When the input resistance value is large and the VDD is gone up at mildly in the vicinity of the released voltage, repeating the above operation may result in the occurrence of output.

As shown in Figure A/B, set R1 to become 100kΩ or less as a guide, and connect CIN of 0.1µF and more to between the input pin and GND. Besides, make evaluations including temperature properties under the actual usage condition, with using the evaluation board like this way. As result, make sure that the cross conduction current has no problem.


  • *1) In the CMOS output type, a charging current for OUT pin is included.
  • *2) Note the bias dependence of capacitors.

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