On the other hand, I cracked open an STPS40L45 today: monolithic. One die, pretty well covering the D2PAK tab area. Die attach looked similar, didn't get a good look at the die top though (cracked, and still embedded in the plastic).
Wouldn't be surprised if they offer single devices of double the rating simply by bonding the two anodes together.
Tim
It turns out not to be true. The post-mortem analysis revealed that the cause of the failure was a high voltage spike caused by load dump: a quick-and-dirty Schottky diode bridge failed in a similar way when the load changed from 10A to 0A. A beefy TVS parallel to the secondary winding should solve the problem by providing an emergency current return path.
Best regards, Piotr
Reading your later posts it looks like you've solved the failure.
Back on the Schottky question, to get 40A safely from the VTB6045C you need to ensure one diode conducts at least 10A.
Reading the data sheets, the Vf curves say that's ensured if the two diodes' Vf matches better than ~100mV @ If=10A.
Cheers, James Arthur
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