Oops! I saw the date stamp and took that as the post number.
No. Speed of decline is not important, only that the comparator threshold is crossed thereby causing the comparator output to change state and generate the interrupt.
That is provided that you include a diode in your circuit.
Edit:
So, assuming that you have a battery powered project, with a switch at the VIN pin of a 3.3v Arduino, like the pro mini...
You could have the switch, diode, capacitor, and divider positioned like this, which would mean that you would have a a much more "instant" detection of power failure when the switch is turned off. If you don't have the diode, then the response time is slower.
Well, sounds like you've already made your decisions, so why ask the question you did? Strange, indeed.
You are being negative for no reason. First of all, I have not made any decision, I merely said what I was thinking about. I am currently not making a design which needs a cut-off detection at this time. This thread right here, I call it "doing research". Sometimes I google things, sometimes I ask people things...
Besides that.... I specifically asked how long an arduino nano or uno would stay active if you cut the power on the Vin pin. Because they have on-board capacitors. But the very first reply already recommended to use external capacitor to be on the safe side. That direction was where this conversation was going to.
And I must say that I am very content with the many answers. That I may or may not use a voltage monitoring chip in my next design does not mean I do not find them interesting or that I don't want to learn more about it. And who knows, if I have need for a cutoff detection in my next design. I may be taking a look at this thread again.
Anyways, the designs and anwsers are clear to me.
Regards,
Bas
EDIT: Original equation was wrong. I've hopefully fixed it now.
This depends on your chosen input voltage into the linear regulator (Vin), the output voltage of the linear regulator (Vout) ,the dropout voltage of the linear regulator (dropout), the current of at the output (Iout), and the capacitance in farads at VIN (farads).
Once you have found these values, you can calculate the total energy you have available (joules)
Then you solve for the time, in seconds
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