If you view some blogs that have sticky ads on them, like Ogbongeblog on mobile devices, you will see the ad that sticks to the top of the blog.
You can’t call that ad an adsense ad unit. It is an ad unit generated from my Sulvo account. Sulvo offers Sticky mobile ad units that show on mobile devices, either at the top or bottom.
So, if you want to add such ad to the top of your Blogger blog, you should sign up at sulvo.com.
If approved, sign in to your Sulvo publisher account and click on the “Inventory” tab. Thereafter, click “New Ad Unit” button, select, sticky mobile option, select “top” as placement, click “create” and add the Sulvo ad codes into your blog html. The ad should display at the top of your blog after some few minutes. Not instantly though.