fractional frequency divider... divide-by-4.5

[jlee]

fractional divider

Hi,

Can anyone please give me references about fractional frequency divider? I want to implement a divider-by-4.5 frequency divider.

Thanks.

 

[eternal_nan]

fractional frequency divider

Hi,

Usually fractional dividers are implemented using an integer divider and then switching its "divide-by" setting between two adjacent settings in a systematic manner. For example, to get 4.5, you would keep the divider programmed to 4 for 50% of the time and to 5 the other 50%. For other fractions, you use other percentage of the two adjacent settings. A better way of doing this (while preserving the same idea) is to use a sigma-delta modulator to toggle between the two settings (you can search for this on the web, lots of material is available). There are other ways to do fractional division, but the above is the best performing/most commong I am aware of.

 

[wkong_zhu]

fractional clock divider

Use sigma delta modulator as divider controler. a 2nd order cascade sigma-delta is most popular, just use adder to implement.

 

[steven852]

clock dividers made easy mohit arora

I am interested in these appraches. Can you provide some examples? Google returns too broad results.

Thanks

 

[Davood Amerion]

divide by 4.5

first double input frequency then divide it by 9
for more detail see this topic:


regards,
davood amerion

 

[AlexWan]

fractional divider sigma delta

Please ref the paper of SNUG 2002 Boston.
"Clock Dividers Made Easy" by Mohit Arora - ST Microelectronics Ltd.

 

[ls000rhb]

clock divider by 4.5

to:eternal_nan
can you give some papers about sigma-delta modulator using in fractional frequency dividers?i want to know how to specify the sigma-delta modulators' structure,parameters.