External clock level translation 3.3V to 5V

Go To Last Post
6 posts / 0 new
Author
Message
#1
  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

My master clock is being generated by a device running on a 3.3V supply. I need this signal to clock an AVR running at 5V. Can I connect it directly or will some level translation be needed? What level translators will work at 20MHz? Suggestions please. :? And before you ask, I can't do it the other way round; the master clock is ultra low jitter type, supposedly better than the AVR crystal oscillator (I think).

If you think education is expensive, try ignorance.

  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

20MHz is no problem for most buffers, even the ones designed for translating between voltages. Take a look at TI's 74LVC1Gxxx single gate parts, for a nice small solution.

Writing code is like having sex.... make one little mistake, and you're supporting it for life.

  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

TYVM. :D I have other signal lines that I was level shifting using other means (voltage dividers), so if I have to add an IC for this I'll move those too to a proper level translator chip.

http://focus.ti.com/paramsearch/...

If you think education is expensive, try ignorance.

  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

http://focus.ti.com/docs/prod/fo...

I'm leaning towards this one. Can handle 60 MHz. Not very expensive either. :D Has anyone used this IC and can give me his/her comments and/or recommendations? TIA.

If you think education is expensive, try ignorance.

  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

Wont a simple HCT be fast enough or a AHCT

Those have a Vil of 2v as any other TTL device.

/Bingo

  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

Even an HC will do in a pinch for the clock. But it will only work in one direction (per IC). :(

Quote:

I have other signal lines that I was level shifting using other means (voltage dividers), so if I have to add an IC for this I'll move those too to a proper level translator chip.

If you think education is expensive, try ignorance.