• State
  • Locked Locked
  • Replies 1 reply
  • Subscribers 97 subscribers
  • Views 500 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

DM6446 and TVP5146 Spread Spectrum

MikeP12806
Intellectual 450 points
Other Parts Discussed in Thread: TVP5146

I'm working on a next generation of an existing design that had some EMI issues (eventually resolved) and am looking at the possibility of using a spread spectrum oscillator to drive the davinci clock and the video clock, but am a little wary about doing so and was looking for some feedback.

Could anyone give some feedback on how stable the DM6446 and/or TVP5146 would be with a spread spectrum clock, let's say 1% down spread to limit the max frequency.  The USB system explicity says int the manual it highly suggests using a 24 MHz crystal, so I'll stick to that, system clock seems the most likely candidate for the spread spectrum and I am warrry of putting it on a converter.

Please let me know your thoughts (Yes, I know I can reduce EMI concerns using other methods layout, shielding, etc..., but am more interested in a discussion on spread spectrum clocking on video systems).

 

Thanks,

Mike

  • 0
    TI__Mastermind 41665 points

    In general in the past the use of spread spectrum clocks has been not recommended, at least in older parts the SSC jitter was not well filtered out by the pll and could 'leak' into the on chip logic, however I have not seen much on this for more modern devices like DM6446 so it may be possible. In any case we do not do any extensive characterization regarding SSCs on the DM6446, so I would still not recommend it as there is certainly some risk that portions of the chip may be affected by the SSC, and we cannot guarantee it will work. I suppose it would not hurt to give it a try, though I would perform some extensive testing before using it in a production scenario.