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TXS Level Converter Powerdown Question

Chris Read
Genius 3345 points
Other Parts Discussed in Thread: TXS0104E, TXS0108E

We are using TXS level converters (TSX0104E, TSX0108E) in our system to translate from 1.8V (VccA) to 3.3V (VccB).  We have situations where we are turning the power supplies off to both sides (VccA and VccB both off) and driving OE low.  However, the supplies for VccA and VccB don't drop all the way to 0V.  VccA drops from 1.8V to about 0.7V and VccB drops from 3.3V to about 1.5V.  Some of the signals on either side of the TXS parts are still active and asserted high.  Is it possible that current is leaking through to the supply voltages through the TSX parts, even though OE is low?

Thanks,

Chris

  • 0
    TI__Genius 9085 points

    For the TXS0104E,  if one side is powered off the other side IS disabled, but it doesn't have IOFF feature, so there is the possibility of leakage current. IOFF feature ensures that there is no leakage current. 

    However, it was my impression the TXS0108E DOES have IOFF. Are you seeing this behavior in both devices?

     

  • 0 in reply to Hattie
    Genius 3345 points

    Thanks for your response, Hattie.

    The 1.8V supplies of both are tied together.  The 3.3V supplies of both are tied together.  So it's not easy to tell if the TXS0108E is exhibiting the problem or not.

    Are you saying, though, that with OE low, and VccA and VccB switched off, that asserted-high voltage levels on the A & B inputs could reasonably raise the voltages on VccA and VccB to the neighborhood of 0.7V for VccA and 1.5V for VccB?

    Thanks again,

    Chris

  • 0 in reply to Chris Read
    TI__Genius 9085 points

    I'm not sure what voltages would be seen, but these do seem like reasonable values to me, if there are active signals on the line.