Re: [avr-chat] AVR on 1 AA bat with just 1 L and 1 C

[Graham Davies]

address@hidden wrote:

 

> I think e.g. ATtiny15 could be operated from just one 1.5V battery
> using just one coil and one capacitor and mis-using the AVR chip to
> act as a switched power supply for itself. Look:
>
>                     ....................
>          coil       :       AVR        :
>     -------uuuuu----:port           vcc:----
>    |                :pin    gnd        :    |
>   ---               :..................:   --- cap
>    =  bat                    |             ---
>    |                         |              |
>     -------------------------+--------------
>
> Strange, is not it? Yes, battery goes to port pin only. Yes, on vcc,
> there's just the cap and nothing else. But wait, I think it could work:
>
> 1) AVR grounds 'port pin', current flows via coil
>
> 2) AVR leaves 'port pin' floating, current still flows via coil and now it

> charges the cap via internal over-voltage protective diode on the pin
>
> Did I miss something?

As other people seem to be taking this seriously, I have to point out that you have missed the need to control the generated supply voltage.  Without control, VCC will just increase until it blows up the AVR or some arbitrary limiting factor comes into play.  Perhaps you think that you have a voltage doubler here.  This is not so.  A boost converter requires feedback from the generated voltage to control the switching mark/space ratio in order to produce the desired output.

 

Thank you for this suggestion.  I think it is an interesting puzzle.  May I have your permission to use it in interview situations?

 

Graham.