SN74HCS08-Q1: Slew Rate Affect

Dajon McGill

Part Number: SN74HCS08-Q1

Hey Team,

My customer has a question, shown below. Can you help to break down the affect of slew rate on the operation of the gate?

"We have a question on the slew rates of the SN74HCS08-Q1 part. Does the slew rate of the inputs to the logic gate affect the timing or functionality of the gate?"

Thank you!

Best,
Dajon McGill

over 3 years ago

0 Clemens Ladisch over 3 years ago

Guru 318050 points

The only effect the input slew rate has is on the time when the input voltage crosses the switching threshold. But once that has happened, the propagation delay to the output is always the same.

0 Dajon McGill over 3 years ago in reply to Clemens Ladisch

TI__Expert 7151 points

I think they were worried about some of the “ultra fast” logic gates going into an oscillation state that could cause a shorting affect. Have you seen/heard of this with any of the parts?

0 Clemens Ladisch over 3 years ago in reply to Dajon McGill

Guru 318050 points

This can happen with all CMOS devices that do not have Schmitt-trigger inputs; see [FAQ] How does a slow or floating input affect a CMOS device?

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SN74HCS08-Q1: Slew Rate Affect