LT8361 has provision for feeding in an external clock (MODE/SYNC pin), and also a pin to set a fixed frequency clock with a set resistor (RT pin). I would like to feed in a spread spectrum clock to the MODE/SYNC pin to try to spread noise out over a greater frequency range and I would like to know what should be done with the RT pin in this case as I cannot tell from the datasheet (see http://www.analog.com/media/en/technical-documentation/data-sheets/lt8361.pdf )
Same question for LT8364 (http://www.analog.com/media/en/technical-documentation/data-sheets/8364f.pdf )
I know that should be possible for LT8650S (http://www.analog.com/media/en/technical-documentation/data-sheets/lt8650s.pdf); see page 23. "A synchronizing signal that incorporates spread spectrum may reduce EMI."
I want to use LTC6909 to create various clocks with different phases but with spread spectrum (http://www.analog.com/media/en/technical-documentation/data-sheets/6909fa.pdf )
Please advise in this regard, or if I have missed something in the datasheet please let me know.
Both, the LT8361 and LT8364 have Spread Spectrum Frequency Modulation SSFM, as one of their features, and precisely for the purpose of helping with EMI.
There is a paragraph on page 11, Synchronization and Mode Selection, which discusses this topic (external synchronization) in some detail.
thanks for your answer.
My question is about the possibility to use an external clock that is already SSFM ("A synchronizing signal that incorporates spread spectrum").
I know already that is possible to use Spread Spectrum XOR external clock, but there is not a single line that say that they could be used togheter. This line ( "A synchronizing signal that incorporates spread spectrum may reduce EMI") exist for LT8650S, does not exist for LT8361 and LT8364.
At page 11 of LT8361 datasheet, I am not able to find any line similar to "A synchronizing signal that incorporates spread spectrum may reduce EMI".
I understand your question, and you are correct, we do not address that issue on the datasheet, and that is because we have not tested for that.
What we have tested is whether the included SSFM feature helps with EMI when enabled, and it does.
I will use the "local" Spread Spectrum clock instead of an external one.