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Single PWM Logic Level Shifter
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Please be positive and constructive with your questions and comments.

Single PWM Logic Level Shifter

by madmacs on Fri Jun 14, 2019 12:32 pm

I'm looking for a small PWM friendly logic level shifter.
Specifically, I'm connecting a Neopixel to an ESP32, but I have an RPi application as well. (I'm using a YF08E on one project right now, don't forget the Enable pin!)
I see a lot of multichannel level shifters in use cases, but don't see any single channel ones.

I also have applications where I am level shifting I2C currently using the BSS138 in a SOT-23-3 package and I am also using a PCA 9306 on another project.
If the BSS 138 would work that would be great. I'm assuming I can omit the PU resistors in this application.

Thanks!

If anyone found any similar items in the forum please feel free to link them here. I did a little searching but didn't find a specific answer in my search.

madmacs
 
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Re: Single PWM Logic Level Shifter

by adafruit_support_bill on Fri Jun 14, 2019 12:39 pm

For driving Neopixels powered at 5v from a 3.3v processor - we recommend the 74AHCT125. https://www.adafruit.com/product/1787
No level shifting is required if you power the pixels from 4.8v or less.

i2c requires something like the BSS138 https://www.adafruit.com/product/757

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Re: Single PWM Logic Level Shifter

by madmacs on Fri Jun 14, 2019 12:53 pm

I saw the 74AHCT125 as a recommendation in the PWM tutorial. It's a big chip and I'm looking for a surface mount.

Would it be fair to assume another SN74AHCT would also work?
I found this one that seems to be a single channel variant.
SN74AHCT1G125

Thanks!

madmacs
 
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Re: Single PWM Logic Level Shifter

by adafruit_support_bill on Fri Jun 14, 2019 1:03 pm

That should do it. Paul Stoffregan of PJRC did some extensive testing a while back and determined that the AHCT variant of the 74125 had the best characteristics for driving the Neopixels. We just have the quad DIP packages in the store. But other configurations should work just as well.

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Re: Single PWM Logic Level Shifter

by madmacs on Fri Jun 14, 2019 1:36 pm

Fantastic! Thanks!

madmacs
 
Posts: 15
Joined: Wed Dec 27, 2017 5:36 pm

Please be positive and constructive with your questions and comments.