SN74LVC2G34: regulating 5v to 3.3v and I see ringing

Robert Oujesky

Part Number: SN74LVC2G34
Other Parts Discussed in Thread: SN74LVC2G17

I am using the SN74LVC2G34 to regulate an encoder signal from 5v down to 3.3v. It does that but I am seeing 394 nanoseconds of ringing on the 3.3v output during the transition. below are 2 images of the same signal, one is just zoomed in a bit more. I checked this forum and this link and the encoder signal is no where near the 160mhz frequency of this FAQ:

https://e2e.ti.com/support/logic-group/logic/f/logic-forum/742805/faq-what-is-the-maximum-data-rate-or-operating-frequency-for-a-logic-gate-or-buffer

I would like to remove this ringing. Any suggestions?

thanks!

over 2 years ago

0 Albert Xu1 over 2 years ago

TI__Mastermind 25635 points

Hi Robert,

Are you able to send a circuit schematic so we can get some more information on your design?

0 Clemens Ladisch over 2 years ago

Guru 280490 points

This might be caused by slow input edges that violate the Δt/Δv limit; see [FAQ] How does a slow or floating input affect a CMOS device? If that is the case, use Schmitt-trigger buffers like the SN74LVC2G17.

0 Robert Oujesky over 2 years ago

Prodigy 10 points

This is somewhat embarrassing as the chip works fine, but my scope is lying to me :( The images in my post are from my Rigol. Much as I did not want to, I hooked up a Tektronix scope just to see.... below is the tektronix image of the same readings. Cyan is the 5v in and yelllow is 3.3v out. NO RINGING.... I like the Rigol because of the big screen, but the Tektronix is a lot faster... anyway, sorry to waste folk's time

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SN74LVC2G34: regulating 5v to 3.3v and I see ringing