Hello Charly,
no, I do not need to know it. It is just that the datasheet should give that information.
Noone can ensure to provide exactly 1.3V. Therefore min. and max. values should be stated
in the datasheet. Lowering the value until the part stops is in my opinion not a practicable way to find
something out that is concealed by the datasheet.
Best regards,
Reinhard