SN74LV244A: spiking on output rising edge

Fred Cheng

Expert 5660 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:

over 1 year ago

0 Clemens Ladisch over 1 year ago

Guru 316400 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 Fred Cheng over 1 year ago in reply to Clemens Ladisch

TI__Expert 5660 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 Clemens Ladisch over 1 year ago in reply to Fred Cheng

Guru 316400 points

The output driver simply connects the pin to either V_CC 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.

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SN74LV244A: spiking on output rising edge