OK, now I see how this works. Sorry I did not gave the proper attention to the AN1072.

It works in reverse. It does supply a 0,6 volts to the ADC input and the refererence is read from the Vdd supply.

Unfortunately this is NOT what Roger wants. He has a stable Vdd from his LDO regulator so his ADRES result will always be the same, no matter the battery condition.

Clever technique but not the one needed here...

Ioannis