A Sprint is a time-boxed period when a Scrum Team works to complete a set amount of work that delivers value to the customer1. A Sprint concludes when the time-box expires, regardless of whether all the tasks, Product Backlog items, or Definition of Done are completed or not23. The Product Owner has the authority to cancel a Sprint if they determine that the Sprint Goal is obsolete or the work done is no longer valuable1.
Therefore, the Product Owner decides when enough has been delivered to meet the Sprint Goal, and the Sprint ends accordingly.