TOPIC: Project Charter not being a controlled document

The exam simulator and prepcast documents say project charter is not a controlled document. Though the PMBOK guide does not list out which project document is controlled or not.

Why is project charter not a controlled document?

The project charter is an approved document that is signed by the project sponsor and authorizes the PM to commit the PM too begin the project and assign org resources. Based on the fact is a signed/approved/authorized document, should it not qualify as a controlled document? I understand the Charter is not baselined, but still approved nonetheless

Is there a PMBOK definition for what is a controlled document?

Vikram,
As I understand compare controlled as version control so for a single phase project project charter is created once and approved. For multiple phase project it may be modified in later phase but remains same in that phase.