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SN74LVC162244A: whether it has no risks when the input slew rate is lower than 10ns/V?

Frank Xiao
Genius 12055 points
Part Number: SN74LVC162244A
Other Parts Discussed in Thread: SN74LV8151, SN74LVC2G17, SN74LVC1G17, SN74LVC3G17

Hi team,

My customer is using the SN74LVC162244A now. We want to check whether it has no risks when the input slew rate is lower than 10ns/V. Could you please provide the details? Thanks,

  • 0
    TI__Guru* 96681 points

    Hi Frank,

    These two signals are not just a little slower than the rated spec (10ns/V) -- one is non-monotonic, the other is very noisy, and both are literally thousands of times slower than the spec (~2750000ns/V for the first one, and ~14000ns/V)... yes, this introduces huge risks for the system (oscillation and undesired triggers) and the device (excessive current will reduce lifetime and possibly damage the device).

    Slow inputs are bad for CMOS devices. There's an FAQ that goes into details as to why:

    The only good solution would be to add a Schmitt-trigger buffer to prevent the excessive current and multiple triggers from those signals.

  • 0 in reply to Emrys Maier
    TI__Genius 12055 points

    hi Emrys,

    could you please recommend a buffer part number here? So the buffer is behind the 2244a or before the 2244a? Thanks.

  • 0 in reply to Frank Xiao
    TI__Guru* 96681 points

    Hi Frank,

    In order to improve the input signal's edge rate, the Schmitt-trigger buffer must be placed before the SN74LVC162244A in the signal path.

    The largest array of Schmitt-trigger buffers that we have available is 10 channels in the SN74LV8151.

    If this issue is only on some channels, then they could go with a lower bit-count device such as SN74LVC1G17 (single), SN74LVC2G17 (dual), or SN74LVC3G17 (triple) to just clean up the channels that are having issues.