[time-nuts] More on SiLabs 5340

jimlux jimlux at earthlink.net
Mon Jan 29 19:04:15 EST 2018


On 1/29/18 3:37 PM, Mark Goldberg wrote:
> Reference my earlier postings titled "SI532X Chips Close In Spurs (Somewhat
> Long)". There are many sets of register values that will get you the same
> output frequency and the clock builder may not give you an optimal set for
> phase noise and spurs. I created a spreadsheet to calculate other sets of
> values and chose one that worked the best. I just did it through trial and
> error of the different sets of values I came up with until I found one with
> low spurs.
> 


We've experienced that here with other PLL chips - For the ADF4108 
integer-N PLL, sometimes there's a big difference between R odd and R 
even (the R is the reference divisor in the fout = fin * (M*B+A)/R

So you wind up fooling around with various combinations of A, B, and R 
to get the spurs where you want them (or, more commonly, to move them 
from where you don't want them)



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