There are a number of ways to manage referential integrity.
You could disable the contraint:
But you wouldn't be able to re-enable it until the data was fixed.
You can configure cascading deletes. This means any record linked through a foreign key would also be deleted.
But this will change database behaviour and allow parent records to be deleted where you may want the presence of a child to create a blocking action.
So in short, no you can't truncate a table without dropping the constraint, but SQL does have mechanisms for helping with referential integrity.