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TPD3S714-Q1: TPD3S714 Clamping Current

Robert Gruich
Prodigy 20 points

Part Number: TPD3S714-Q1
Other Parts Discussed in Thread: TS3USB221

Does the TPD3S714 have a maximum clamping current for I/O? 

In an open GND condition, I measure -0.6V at the I/O pins of the TPD3S714 with respect to its GND pin; which is beyond the Absolute Max Rating of -0.3V).  In this state, the leakage current is only 600uA.  The TPD3S714 worked fine after exposing the device to these conditions, but I'd like to confirm if it is OK for long-term reliability.

For reference TPD3S714 Abs Max Ratings:image.png

 

For reference, the type of parameter I'm looking does appear on TS3USB221 datasheet:

image.png

  • 0
    TI__Genius 15071 points

    Hi Robert,

    There's no i/o current clamp to my knowledge.  The -0.6V is likely the diode from the ESD cell.

    I'm a little confused by your measurement.  If you have open GND, what are you referencing the IO pin to?  How are you measuring this voltage?

    Thanks,
    Eric

  • 0 in reply to Eric Hartigan
    Prodigy 20 points

    Thanks Eric,

    Below is an illustration of my setup and measurement. 

    VBUS and data connections are made to the Host.  Host GND is disconnected from my board's GND.  My board floats up to the Host VBUS potential which brings my board's GND to a higher potential than Host GND.  This creates a leakage path (yellow) through the IC ESD protection structures and back to Host GND through the data line(s).

    I'm measuring my board's GND with respect to Host GND and measuring the D+ line with respect to Host GND.  The difference is the voltage seen at the IC's VD+ with respect to its GND.

    I'm hoping to understand if -0.6V on VD+ with respect to the IC's GND can be considered safe as long as the leakage current is kept low.

  • 0 in reply to Robert Gruich
    TI__Genius 15071 points

    Hi Robert,

    Thank you for clarifying.  I am still looking into this and should have feedback by the end of today.

    Regards,
    Eric

  • 0 in reply to Eric Hartigan
    TI__Genius 15071 points

    Hi Robert,

    The device was not designed to handle this loss-of-ground scenario.  While the ESD structure is there to protect against transient events, I can't guarantee -0.6V is acceptable for long term reliability.

    Regards,
    Eric

  • 0 in reply to Eric Hartigan
    Prodigy 20 points

    Thanks for this feedback, Eric.  Can you recommend any USB High Speed protection IC that is designed to handle the loss-of-ground and/or rated to reliably survive this level?

  • +1 in reply to Robert Gruich
    TI__Genius 15071 points

    Hi Robert,

    We don't have a device that specifically targets this use case.  The event of having the host IC losing its ground connection to the USB port on the other side of the cable is outside the scope of our protection parts.

    Regards,
    Eric