Using Sprite Atlas with Asset Bundle

Can someone, please, explain me how the sprite atlas works with asset bundles? I'm having a hard time to make it work.

If I put my sprite atlas in the bundle do I need to keep the original sprites in the bundle as well?

I've tried to build the asset bundle with just the atlas and the size of the bundle is bigger than the one without atlas (and just the original sprites) it's not logic to me.

Any guide of sprite atlas + asset bundles will be more than welcome