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

[duffy]

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.

 

[Jamdan]

Howdy OlPhart!

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

 

[OlPhart]

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...

 

[Jamdan]

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.

 

[Reloadron]

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.

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

Ron