Re: Low voltage shutdown


Apr 16, 2003

 


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#910 Apr 16, 2003

I amdoing an AD measurement and I need to display it correctly.  For that tohappen, I think I need a constant voltage.  For example, if I am using Vrefas the 5 V Vdd, and Vdd drops, then my measurement will be wrong.  Thevoltage I am measuring is coming from an off-board sensor. I haveadded a voltage regulator so that I have a constant 5 volts, and will run it onbatteries of more than 5 volts.  But I would like to shutdown completelyrather than display wrong results.  I could measure the regulated volts,but since that would be referenced to Vdd, it wouldn't help. Doesanyone have a suggestion on how to do this? Bruce Partridgewww.rebreather.caVancouver, Canada

 



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#912 Apr 16, 2003

There are a ton of precision voltage reference devices available.

Maybe if you picked one the held +2.5V you could check to see if the

A/D got the right answer.



Among many other places, check www.maxim-ic.com/References.cfm. Note

that there is also an application guide on using precision references.



Good luck!

--- In piclist@yahoogroups.com, Bruce Partridge bgpartri@c...> wrote:

> I am doing an AD measurement and I need to display it correctly.

For that

> to happen, I think I need a constant voltage. For example, if I am

using

> Vref as the 5 V Vdd, and Vdd drops, then my measurement will be

wrong. The

> voltage I am measuring is coming from an off-board sensor.

>

> I have added a voltage regulator so that I have a constant 5 volts,

and will

> run it on batteries of more than 5 volts. But I would like to

shutdown

> completely rather than display wrong results. I could measure the

regulated

> volts, but since that would be referenced to Vdd, it wouldn't help.

>

> Does anyone have a suggestion on how to do this?

>

> Bruce Partridge

> www.rebreather.ca

> Vancouver, Canada

>

>

>

> ---

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