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Design >> Mixed-Signal Design >> PLL divider ratio
https://designers-guide.org/forum/YaBB.pl?num=1177232433

Message started by chase.ng on Apr 22^nd, 2007, 2:00am

Title: PLL divider ratio
Post by chase.ng on Apr 22^nd, 2007, 2:00am

Hi all,

I notice that most motherboards are having 14.318 MHz, anyone has idea what is the divider ratio to generate the system clock at 133 MHz/200 MHz?

thanks and regards,
chase

Title: Re: PLL divider ratio
Post by mg777 on Apr 22^nd, 2007, 12:16pm

The 14.318181... MHz is some multiple of the color subcarrier in TV's, and dates to when early computers used TV's as monitors.

To answer your question, 100 = 14.31818181... * 440/63

In practice there will be a ppm spec on the crystal, and a steady-state error in the PLL.

Title: Re: PLL divider ratio
Post by adesign on Apr 25^th, 2007, 9:47pm

It also depends on the maximum divider settings allowed on motherboard.