Using diode breakdown voltage/similar to determine if voltage is over a given value

You could just buy a thing like this for $26 - http://search.digikey.com/us/en/products/CC10-0505SF-E/445-2431-ND/920391

4.5 - 9V in, 5V @ 2A out, $26.

Might help to give us an idea what you are trying to accomplish, there's probably much better ways of doing it. For instance, if you need a precision voltage reference for instrumentation, you would use a separate voltage reference - trying to get the reference off the power supply for the rest of the circuit is like trying to make a precise clock in your car by gearing it to the wheels and then trying to make the car run at a constant speed.


OlPhart - voltage subtractors aren't new, and if you have a -3.3V regulator that gives you 1.7V from a 5V source, it gives you 1.95V from a 5.25V source.

Howdy OlPhart!

Your suggested solution is very intriguing, and I love the outside the box thinking.

Howdy, Jamdan: appreciate the thought.... try it, It's impressively obvious. I stumbled onto it in conversation with a another designer, and we both laughed our butts off.... How simple yet elegant.

I think it's a great way to determine a battery level that's above your ADC input max. I use it on a project of a 24V battery sourced system (lawyers tell me to stop here...). Enjoy & L8R <<<)))

Duffy: never said new, just new to me....., But derived Not told to...

Hi Duffy,

Boy that one looks perfect (except for the price). All the numbers are where they need to be.

I am trying to find a solution to this for a relative of mine, and I don't know if he would want me to say more (even though it is fairly ordinary). He is a young guy (still in school) and would need several/many of these, so price is a consideration.

So far the TPS 63002 at $1.50 seems to be front runner. Everything on it is perfect except that the maximum incoming voltage is 5.5v, which would probably be fine 99% of the time. I have sent an email to TI to ask what happens if the incoming voltage is over 5.5v.

I see the TPS 63002 as a fine and economical choice. Early on it was I believe mentioned this would be driven by a computer 5 volt rail. I have never seen one exceed 5.25 volts which at 5% falls into the allowable tolerance. Other solutions like the one I pointed to aren't by any means cheap.

I am trying to find a solution to this for a relative of mine, and I don't know if he would want me to say more (even though it is fairly ordinary). He is a young guy (still in school) and would need several/many of these, so price is a consideration.

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Had I been aware of that I would not have suggested the more expensive solution.

Ron