SN74LVC1G3157: question about "Δt/Δv Input transition rise or fall rate"

Ben Kuo

Expert 6715 points

Part Number: SN74LVC1G3157
Other Parts Discussed in Thread: SN74LVC1G17-Q1

Dear team,

If rise/fall time of input signal are over datasheet "Δt/Δv Input transition rise or fall rate" spec.

Is that possible to damage device?

I found E2E post about Δt/Δv limit .

The Δt/Δv limit applies only to the digital control input S. If the S signal actually is too slow, you have to add a buffer with a Schmitt-trigger input (e.g., SN74LVC1G17-Q1) in front of it.

If S signal too slow, we need to add buffer.

What if S signal too fast? any risk about this?

Regards,

Ben

over 2 years ago

0 Clemens Ladisch over 2 years ago

Guru 243820 points

The S signal cannot be too fast.

When the S signal is too slow, the device might indeed get damaged over time. See [FAQ] How does a slow or floating input affect a CMOS device? and the application report Implications of Slow or Floating CMOS Inputs.

0 Parker Dodson over 2 years ago

TI__Mastermind 43436 points

Hi Ben,

As Clemens indicated too fast isn't really an issue - there is some capacitance on this pin but it is low at 2.7pF. However if the signal speed is too slow one of the largest issues is that when the S pin's voltage is between VIL(max) and VIH(min) the switch is in an undefined state and excessive current can possibly be shunted from VCC to GND. The FAQ Clemens posted is a good resource as is this application note we have on the subject: Implications of Slow or Floating CMOS Inputs.

But yes adding a Schmidt Trigger Buffer is work around if the S signal is too slow.

If you have any other questions please let me know!

Best,

Parker Dodson

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SN74LVC1G3157: question about "Δt/Δv Input transition rise or fall rate"