Although the title is blunt it is unfortunately exactly what is occurring, the chip is ending up shorting the input. It's now a real worry as I have it ready for two upcoming products. For one prototype I have 5 of these chips, the 3rd blew yesterday, I replaced with a 4th which instantly blew and I'm now on the 5th, which so far is working. Once blown the input measures 0.04ohm, so a direct short. At a guess an internal FET has failed.
Situation
The TPS61022 is currently boosting voltage from a current restricted supply of just 50mA (this blew the 4th). The input voltage ends up around 3V while the EN pin ends up at either equal to the output or about +0.4v above the input as part of the bootstrap operation. This is best shown with a schematic.
AC2 is presently a 6.5v DC 50mA supply. There is no load (or about 10mA max so basically nothing on the output of the TPS). The Vdd voltage is "var". The EN pin is attached to "Awake". The output of the TPS "5V" latches the EN pin. Once the voltage drops are factored in it's about 3.5V at the TPS Vdd.
As the 5551 has a voltage drop of about 1.2V and the 1n4448 is about 1v the EN pin can be slightly higher than the input voltage upon startup. There is nothing in the datasheet to say this isn't allowed but it is the only thing I can think of and is worth confirming.
The circuit itself is working fine, boosting to 5.25V. I haven't tried with any real load as my primary agenda is to find out why the chip keeps destroying itself.
