What are SD/SS, delay, and flag pins on LM2596?
It seems that TI updated a number of its LM25XX datasheets in May, and they made several goofups in and between them. The pins you ask about are found in the LM2593HV and LM2599 devices, but not in the LM2596. The previous revision of the datasheet (revision C, document SNVS124C) does not contain the unusual additions.