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TXB0104: Possibility of damage at VCCA > VCCB with OE pin pulled up to VCCA

S.Satoshi
Guru 21685 points
Part Number: TXB0104

Hi,

Please give your comment if there is possibility of damage to VCCA, VCCB and OE pin under following condition.

  • OE pin is pulled up to VCCA
  • VCCA=OE=1.8V and VCCB=0V (VCCA>VCCB)

Best Regards,

Satoshi / Japan Disty

  • 0
    TI__Guru 62240 points

    Hi Satoshi san,

    Please refer to the app note "Biasing requirements for TXS, TXB and LSF" for information regarding your query.

    When Vcca>Vccb, there will be current flowing through the fwd biasing diode which can affect the reliability of the device. I would not suggest doing this under normal operation, but except for during power ramp up/down.

    please let me know if you have anything else.

  • 0 in reply to ShreyasRao
    Guru 21685 points

    Hi ShreyasRao,

    Thank you for your comment. From this app note, I understand that the Vcca>Vccb condition can not be recommended. However the test condition of ICCA and ICCB in electrical characteristic show Vcca>Vccb condition as below. The customer may understand that you allow to use this condition. But is your answer still that Vcca>Vccb condition can not be recommended?

    Best Regards,

    Satoshi

  • 0 in reply to S.Satoshi
    Guru 21685 points

    Hi ShreyasRao,

    Here is the Fig 6 from app note "Biasing requirements for TXS, TXB and LSF". This shows that ICCA goes up > 1000uA at VCCA=3.5V and VCCB=2.5V. However the electrical characteristic in datasheet show that the maximum ICCA is 2uA at VCCA=3.6V and VCCB=0V. Please let me know the reason of this difference.

    Best Regards,

    Satoshi

  • 0 in reply to S.Satoshi
    Guru 21685 points
    Hi ShreyasRao,

    Or do you mean that VCCA>VCCB condition is acceptable at OE pin is pulled low?

    Best Regards,
    Satoshi
  • 0 in reply to S.Satoshi
    TI__Guru 62240 points
    Hi Satoshi-san,

    Definitely, the normal operation will not be recommended.
    Vccb at 0V, will put all the IOs are in hi-Z. According to the datasheet, the Iccx current will be limited. I will do some more research on this and get back to you. I will see if there are any char data available in this regard.
  • 0 in reply to ShreyasRao
    TI__Guru 62240 points
    Satoshi-san,

    on the datasheet section 10, for power supply recommendations, it mentions that the same statement regarding the outputs in Hi-Z during OE being low or either of the supply Vccx low(0V). It does not mention anything more about Icc except for the electrical char.
  • 0 in reply to ShreyasRao
    TI__Guru 62240 points
    Hi Satoshi-san,

    I researched more into this and you can do it at Vccb at 0V and Vcca > 0V without negatively affecting (increasing ) the current consumption.
  • 0 in reply to ShreyasRao
    Guru 21685 points

    Hi ShreyasRao,

    I really appreciate for your support. I clearly understood.

    Best Regards,

    Satoshi