question on fractional N pll!

[kimiyang]

I am designing a delta sigma pll,how to change the integer N number?
for example :the divider ratio is 133.28 ,135.28,136.28,how to realize them?
what's the arithmetic?

 

[khouly]

the pulse swallow divider can do this , by using dual modules counter , and M , N counters

the pulse swallow divider will be able to get ur divide ratios


khouly

 

[kimiyang]

i have thought about it ,but i don't got it .
can you give me some advice? or papers on this?

 

[khouly]

u can begin with this appnote by TI

www.lebanon-guide.com/cgi-bin/cgt/nph-proxy.cgi/000111A/http/focus.ti.com/lit/an/swra029/swra029.pdf


khouly

 

[kimiyang]

thanks

 

[xwcwc1234]

What is the difference between fractional-N PLL and traditional fractional PLL ? Any examples on this two circuits?

 

[kimiyang]

there is no difference between the two .it 's the matter of definiens.

Added after 8 minutes:

to khouly!
I read this appnote yesterday.it's very useful.
Is there other way to implement the N/N+1 in sigma-delta pll?