automatic VDD regulation

Is there an approach to have a PIC like a 16F688 self regulate it's supply voltage?

Since it operates on 2 thru 5.5V, if I have a 7VDc incoming through an RC delay couldn't the PIC PWM a (weak pull up) pass FET based on it's comparator being referenced to a precision reference?

Once the PWM frequency is hi enough a small RC filter can smooth the power.

Anyone care to ring in on this pls? Nigel, Eric, Mike(s), Colin(always got a hack) etc?

Have you considered using one of the "HV" devices which have a built-in shunt regulator?

Yes...That's a possibility. But I was hoping to use the Oshonsoft Basic to do this. It doesn't yet support those PICs.

Check this out **broken link removed** and the rest of the story **broken link removed**

And this page is better **broken link removed**

It shows the same circuit as the first but has some more cool stuff.

Thx burt!

It's an interesting idea but is it really worth all that complexity?

If you have 7v input and need 5v the efficiency of a SMPS buck may be equal or even less than a good linear regulator. So you don't get any gains.

Instead of all the external parts and things to go wrong with a buck regulator, you could just use a low quiescent current low dropout 5v regulator, a simple 3pin device, and many are internally protected for overcurrent, overheat and even reverse battery connection.