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TXS0108E: Excess Power Draw on Vcc

Part Number: TXS0108E
Other Parts Discussed in Thread: TXB0108,

Hello TI People,

I'm evaluating the TXS0108E and TXB0108 and when in a standby mode the TXB draws approximately 500uA more current than the TXS. Is this correct or do I have a broken chip?

Thanks

  • Hey Angela,

    This behaviour is actually to be expected from these devices. The TXS has two internal 10k pullups on it that will typically draw current when not translating. The TXB series of parts have buffers in them and as a result don't have these internal pull ups which makes them not need to draw that "standby" current as you call it. I have actually seen someone with this issue before and this forum post should help you out.

    If this answered your question please hit the green verification button so we know that we could lend a hand to solving your problem! If you have any additional questions just send them along and I'll work to get them answered for you.

    Best Regards,

    Nick

  • Is it TXS or TXB device which has higher current draw ?
    Please send out a schematic which we can look at.
  • Hey Nick,

    Thanks for the reply, it would appear that the situation I have is the one that you describe. Would the TXB work for my application if the TXS does?

    Thanks
  • Hey Angela,

    That really depends, I see from the other post I'm helping you with that you're trying to use I2C signals, which as mentioned are open drain. This makes the TXB a non-option for that role. If this is for another signal set you can use the TXB if you follow the datasheet specs since it is similar to the TXS. A main one to look out for is the drive needs. The TXB is only capable of approximately 20uA of drive and <70pF of capaciive loading. I hope this helps

    If this answered your question please verify the solution by hitting the green answer verification button below! If you have additional questions, feel free to send them along too.

    Best Regards,
    Nick
  • I see, what is the reason for this?

    Thanks
  • Angela,

    The reason for this is that the protocols the two chips were designed for are different and need to meet different needs. You can find more information about this in the documents that support the two architectures of TXB and TXS. These documents have everything that you'll want to know I'd suspect.

    If this answers your question please verify the solution below by hitting the green verification button below! If you have any additional questions on this topic feel free to send them my way. If they are about other topics please post them to a new thread for better organization of our data.

    Best Regards,

    Nick