We've been testing brown-out recovery (lowering Vin below operating threshold) on a card with 3 TPS54626 supplies.
Results are:
TPS54626 3.3V 3A supply - always recovers.
TPS54626 4.2V 4A supply - always recovers.
TPS54626 5.0V 3A supply - consistently fails to recover.
- All supplies power up normally, but only 2 recover from brown-out.
- Failure is independent of load. Supply will fail to recover even with light load.
- Supply appears to be stuck in a periodic recovery attempt after initial Vout recovery attempt ("T"). See plot of Vout recovery failure below.
- Supply recovers after strobing enable input.
Schematics available for the asking. All 3 supplies were designed in Webench, and operate properly at nominal Vin (12V, 5A) from a normal power cycle.
Is it possible that one of the part's protection features is misbehaving as designed Vout approaches Vout(max) of 5.5V?
