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SN74LV244A: spiking on output rising edge

Fred Cheng
Expert 5340 points
Part Number: SN74LV244A

Hi team,

customer use this buffer to drive the signal from scalar to multiple LED drivers.

but they found the output of our buffer has spiking at rising and falling edge,

they try to add a series resistor 50ohm at output but it didn't work.

please guide us on next step, thanks

input:

output:

  • 0
    Guru 290770 points

    This is likely to be a measurement artifact; to minimize the length of the ground loop, ensure that the oscilloscope probe does not use a ground clip but a ground spring.

    LV-A outputs have an impedance of roughly 30 Ω; you can keep the series resistor.

  • 0 in reply to Clemens Ladisch
    TI__Expert 5340 points

    Hi Ladisch,

    they already used barrel and tips and measure directly between the output pin and the ground pin of the IC, that’s why I found it strange and post this forum.

    is there any other suggestion?

    thanks

  • 0 in reply to Fred Cheng
    Guru 290770 points

    The output driver simply connects the pin to either VCC or GND; the spikes are a result of all the capacitances and inductances in the board.

    Ensure that the '244 has a decoupling capacitor, as near the supply pins as possible.

    Measure after the source termination resistor.