I actually think you will need to clear immigration as CDG will be your entry point from outside the Schengen area. The CDG-TXL flight will basically be the equivalent of a domestic flight.

All that said, even clearing immigrations and security, 1:40 should be plenty at CDG. Although there are no guarantees on a split ticket, if your arrival from ATL is delayed such that you miss your onward flight, there is a reasonable chance that AF will still place you on the evening flight to TXL. Things like that are one of the actual strong parts of the DL/AF/KL partnerships in general (can't say the same for rest of SkyTeam).