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SN74LVTH125PWR transient specification

Bertram Brummer
Intellectual 1906 points

Hi,

my customer is using the SN74LVTH125PWR in a  backplane architecture and  the datasheet is tellign as a recommended operating condition ot have a max. input transient rise and fall time of 10 ns/V.   When they meaasured their application pulling the driving board out they see than transients in the range of 360 - 120 ns/V and therefore violate this spec.

They fear that this could cause some high current thru the two transistors at the input and therefore cause some reliability or a reduced lifetime.

Can somebody tell me whether this is the case or if there is not issue to the device at all ? (Note the transient comes from a diode and 3k3 resistor pull to 3.3 Volt)

Thanks and best regards

  • 0
    TI__Guru* 97046 points

    Hi Bertram.

    The situation you describe here is a 'slow CMOS input' which is described in detail in the app report "Implications of Slow or Floating CMOS Inputs."

    The short answer is, yes - this can cause serious issues for the lifetime and operation of the device.  The solution is to use a Schmitt-trigger input device.  I'm afraid the picture above didn't come through for me, so I can't comment on the schematic.  I don't know of a direct replacement for the LVTH125 that has Schmitt-trigger inputs, but I can do some digging if you like.

  • 0 in reply to Emrys Maier
    TI__Guru 62270 points
    Bertram ,

    if you want to post schematics and or hyperlinks use the " Use rich formatting " .
    And as Emrys pointed out , the slow inputs cause the CMOS turn on off intermittently causing outputs to oscillate (device operation problem ) while also drawing currents which can be damaging to the device over long periods . This would be a reliability problem for the device .