Thank you marco for that reply .
If you look at the icl7660 data sheet you will see in the example of
the positive voltage doubling example requires two diodes in the output so you get 2 Vf diode drops , and then you'd get another two Vf drops if your cascading them again I think .
The maxim chip and the one you linked to don't seem to need diodes on their output in order to double voltage . That's why I asked ,because of this difference in the way the caps and diodes are connected on the icl76660 chip , I don't think
that the trick of using one device to triple voltage will work . ?