Newly designed from the bottom or ground up...

from scratch is correct, to be sure. But it sounds slightly like how one makes a cake as opposed to using a box mix.. you "scratch" and "scrounge" around for ingredients.. It can sound a bit like chickens scratching around in a coop for food..
For something that's meant to sound highly technical, such as electronics.. the word "scratch" here sounds slightly like a hausfrau in the kitchen.. For high tech ad copy for men.. it might be slightly better to avoid it.. just a slight advertising consideration..

From scratch is ok in BE - to my BE ears, it doesn't have the connotations mikestorer mentions.

See the example sentences here:
http://www.oxforddictionaries.com/definition/...
From the very beginning, especially without making use of or relying on any previous work for assistance:
he built his own computer company from scratch
It is a direct reversal of the previous policy where SAS would build its own tools from scratch.
Erase everything on the computer's hard drive and start over from scratch.
This would give it a cheaper entry to the market, although it would have to start from scratch in building a customer base.