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SN74LVT16244B: about the input of SN74LVT16244

Vera Mao
Expert 5065 points
Part Number: SN74LVT16244B
Other Parts Discussed in Thread: SN74LVTH16244A

Hi dear supporting team,

is there any pull up or pull down circuit at SN74LVT16244 input? tks a lot!

  • 0
    TI__Guru* 97046 points
    Hi Vera,
    The SN74LVT16244(B) does not have any internal pull-up or pull-down resistors.

    We do have the SN74LVTH16244A that contains bus-hold circuitry on the inputs to avoid floating inputs, but I don't know of a similar device with pull-down resistors.
  • 0 in reply to Emrys Maier
    TI__Expert 5065 points

    hi Maier,

    thank you for the reply!

    customer is using the chip in below scenario,  the 3 chips A,B,C are in different brd with common GND and share different power supply sources. 

    they are wondering whether below cases will destroy the chip or not. From the absolut rating, I think it will not,  am I right?  tks a lot!


  • 0 in reply to Vera Mao
    TI__Guru* 97046 points
    Assuming the worst case scenario, if 244 (A) is driving the line to 3.6V and 244 (B) is driving the line to 0V, then the current sinking into 244 (B) would be: 3.6/200 = 18mA.

    The Absolute Maximum Ratings table lists the maximum input into any channel in the low state as 128mA, so 18mA is no problem.

    Can I ask why they want this setup? It's generally a bad idea to have bus contention - even though the parts A and B won't break, the 244 (C) will have an unknown and possibly oscillating input (actually, very likely oscillating due to the forced Vcc/2 voltage at the input during bus contention). It will also likely have excessive current draw due to the Vcc/2 input.