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SN74LVTH244A: Two batches SN74LVTH244A have different performance

Frank Xiao
Genius 12055 points
Part Number: SN74LVTH244A

Hi team,

My customer is the SN74LVTH244A now. The input is the I/O of MCU without pull up or down resistor. When use the first batch SN74LVTH244A, the output thinks it's lower voltage and show the low at the output. When use the second batch device test, the outuput has high output and low outptut. The frist batch mark is 47AG3P1X4, the second batch mark is72KG4CNL6.

In my opinion, the input has high input resistence, so it's normal.Could you please help me double check? 

Thank you.

BR

Frank

  • 0
    Guru 243820 points
    What is the voltage that the MCU is driving at the pin?
  • 0 in reply to Clemens Ladisch
    TI__Genius 12055 points
    Hi Clemens,

    The voltage is 3.3v. We want to check the default condition. Thanks.

    BR
    Frank
  • 0 in reply to Frank Xiao
    TI__Guru* 96591 points

    Hi Frank,

    If you are looking for the power-on state of the bus-hold latches for the SN74LVTH244A, I'm afraid there is not one.  Each input pin has a weak latch on it, and because of how latches work, there is no way to know which state it will start in.

    There are two ways I know of to force a starting condition.  One would be to add an external capacitor from the input to ground.  While this is likely to work, it also will make it more difficult for the line to be driven, so I would prefer to go with the second option.

    The second option is to place a large pull-up or pull-down resistor (≥ 100kΩ) at the input.