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SN74CBTLV3245APWR question

Patrick Chen
Mastermind 8875 points

Other Parts Discussed in Thread: SN74CBTLV3245A, SN74LVCC3245A

Hello 

   Customer have a question about SN74CBTLV3245APWR. In their design. The VCC is 3.3V. And the OE_N is control by CPLD. Its power rail is 3.3V_AUX.

   So the OE  is driven HIGH before VCC. Will this cause the leakage path? Thank you. 

BR

Patrick

  • 0
    Guru 74080 points

    Hi Patrick!

    If an input voltage is +0.5V higher than the supply, the internal diodes will turn on. If you do not limit the current through the diode they might get damaged. The maximum current is 50mA. A current limiting resistor might do the job here. Inputs have very little capacitance, so the resistor can be quite large.

    Please see below.

    Dennis

  • 0 in reply to Dennis Eichmann
    TI__Guru 63280 points
    Hi Dennis ,

    Thanks for the contribution to the logic e2e community. I appreciate the support provided to all the members out there ; including me to respond in a timely manner.
    The datasheet of sn74CBtLv3245a indicates that the input voltage range(OE) doesn't have ESD connection to Vcc.
    The device also contains ioff circuitry which helps in preventing the current flowing back through to Vcc when inputs are powered up before Vcc . the ioff spec is provided in the datasheet electrical char.
  • 0 in reply to ShreyasRao
    Guru 74080 points

    Hi Patrick, hi ShreyasRao!

    I'm so sorry, I got my information from this table:

    As you can see I marked the part number in red. I looked at a wrong datasheet. I typed "SN74CBTLV3245" into Google and it suggested "SN74LVCC3245A" as one option and I clicked on that. But it is a different part. I did not notice it. Now when I clicked on the link for the part in your post, I was wondering about the different datasheet. But is it the same for this part? If so, I misunderstood the table, then double sorry!

    Sorry Patrick!

    Dennis