"to circle back with you" means to "follow-up with" or come back to something that was previously discussed. An example would be if you and I had talked about having lunch in the future but haven't made definite plans, I could say in a couple days: "hi kotokoto, I wanted to circle back with you to see if you still wanted to have lunch tomorrow".
I use this phrase more in business or professional situations when setting up meetings rather then with friends. Hope that helps!