Square will be going into his eighth season in the league and seventh with the Chargers. He has appeared in every game the past three seasons, including 15 starts.
The 6-foot-2, 293-pound nose tackle had a career-high 56 tackles last season, including 11 against the Chicago Bears on Oct. 27.
Square has appeared in 75 career games with 23 starts. He has 100 tackles, 10 tackles for loss and 5.5 sacks.