Disconnected from multiplayer when switching applications (full screen)

When I play on Realms server and my Minecraft is on full screen mode, I use to listen to music on Spotify. When I try to change music while playing Minecraft, I use CTRL + TAB to switch to Spotify, but when I come back to Minecraft, the Realms server freeze for me for like 5 secs and after that it log me out with "Disconnected from server".

/Again, sorry for my English. I hope you understood me.