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TPS54020 RT/CLK Clock input requirement

Frank L
Prodigy 190 points
Other Parts Discussed in Thread: TPS54020

Hello,

I would like to use a spread spectrum clock.

Does the TPS54020 accept it? Which constraints do I have to consider?

The data sheet (8.4.6) contains a duty cycle range 20%-80%, and frequency range 200kHz to 1200kHz. Is anything else required?

Regards - Frank

  • 0
    TI__Guru**** 191445 points
    I have never tried it with TPS54020, but I have done some informal testing with a similar device. I used plain linear FM modulation of the clock signal. Up to 5 kHz frequency spread, the internal PLL kept phase and frequency lock. Between about 5 kHz and 10 kHz variation, the frequncy lock was maintained, but phase integrity degrades as frequency increases. Above 10 kHz, it could not frequency or phase lock.
  • 0 in reply to JohnTucker
    Prodigy 190 points
    Thank you John,
    I want to improve EMC test results, so the goal is e.g. 900kHz to 1100kHz (random modulating waveform).
    With this information, it seems impossible.
    Has however anyone "positive" experience with exactly this part TPS54020?
    Best Regards
    Frank
  • 0 in reply to Frank L
    TI__Guru**** 191445 points
    I only tested one device. It was maybe 10 years ago, so I do not remember any more details.