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TPS62143: TPS6214x issues

Bruce Naylor
Prodigy 70 points
Part Number: TPS62143

Needing more mA'age than USB 2.0 VBUS can supply, I'm using a TPS62143 from a 12v mains supply (PVIN connected to AVIN).

If I tie EN to 12v then all is good.

If I tie EN to VBUS (ie 5v) so I get power only when USB connected, then all is good if the 12v supply is active.

If I connect VBUS before 12v then the part appears to briefly powerup, then permanently die. 

Can someone please point me to the section in the datasheet that explains why this is a bad design idea please 

Kind regards

Bruce.

  • 0
    TI__Mastermind 26740 points

    Hi Bruce,

    • To clarify, when VIN (12V) is available first and then you toggle EN high via VBUS (5V), the IC works fine. And when 12V VIN is not available first but EN is powered up via VBUS (5V), the part is damaged?  Is this correct?
    • Can you get the part to work again if VIN(12V) is made available before VBUS (5V)?

    This may have to do with EN max voltage rating (section 7.1 in datasheet) which is VIN+0.3V and powering up EN before VIN violates this. Can you please share a schematic so I can review? 

    Thanks,
    Amod

  • +1 in reply to Amod Vaze
    Prodigy 70 points

    Hi Amod,

    Q1. Correct.

    Q2. No, the device appears damaged at this point. 

    I think section 7.1 explains it well, and in hindsight it was a rookie error. It is unfortunate the issue did not show up on the prototypes or pre-production units, but only once we committed to the 1st production run.  An example in the datasheet with separate  EN would have been useful to highlight the potential dangers here.

    The design was lifted from WEBENCH with the exception of the EN modification.