Oh - now that I'm at a piano I see what you are doing.

This is a fairly common ending cadence if the melody ends on the root. I use it in Darn That Dream - key of G. Last cadence: Am7 D7 Gmaj7. Melody note G. Sub Ebmaj7 - if you want to resolve to the home key Ebmaj7 Abmaj7 Gmaj7.