ADC'ing higher DC voltage dilemna

[tumbleweed]

I see a lot of references to using the internal clamp diodes of chips for a number of purposes.

Those interested may want to read the following Microchip documents:
TB3009 (http://ww1.microchip.com/downloads/e...tes/93009A.pdf)
TB3013 (http://ww1.microchip.com/downloads/e...tes/93013a.pdf)

And then see if they still want to recommend doing this.

[HenrikOlsson]

Hi,
That's an excellent read, thank you for the links!
As with most things the way you choose to do something may differ from time to time and recommendations changes. There are limitations to using the internal diodes, as described in those docs but, depending on the application it may still work fine.

However, passing current thru the internal diode kind of defeats the purpose (I didn't think it thru properly). The idea was to disconnect the voltage divider from ground to lower the current consumption but if we're passing current thru the pin diode (or external diode) into Vcc we haven't gained much....ooops.

Perhaps a second MOSFET or analog switch in series with the pin....

/Henrik.

[ardhuru]

Hank, take a look at http://www.electricstuff.co.uk/picav...tery%20voltage

Its precisely what you are looking for. And while there, do check out the other neat things on the home page!

Regards,

Anand

[HankMcSpank]

Hank, take a look at http://www.electricstuff.co.uk/picav...attery voltage

Its precisely what you are looking for. And while there, do check out the other neat things on the home page!

Regards,

Anand

Thanks Anand mate ....a clever low parts count solution - job done! (curious as to how long that tranny is switched on to allow an ADC sample of the potenetial divider junction voltage to take place though!)

(thanks Henrik & tumbleweed for the input too)

[ardhuru]

I'm glad it worked for you. Did you actually try it out yet?

Anand

[HankMcSpank]

No not yet....another 2-3 days before I get around to knocking up the associated circuit on breadboard - I'll report back.