ADM3251E power consumptin @ 3.3V

Hi, 

I'm not quite sure if the current consumtion while powering the ADM3251E at 3.3V is just = 2.5 + 12 + 6.2 =  20.7 mA like the datasheet seems to display. The concerns comes from comparing it to the consumption when it is powered up with 5V. I know the internal DC-DC is not enbled on the fist case but still, it's such a big difference in consumption comparing powering it up with 5V or with 3.3V.

Can some one please give me a hint? 

Thank you very much.