Best Way To Generate 2 Clocks - 33 MHz & 64 MHz

[swb1]

Hi,

Instead of using 2 separate oscillators, is there a way to generate both 33MHz and 64Mhz with 1 device?? The values don't divide evenly. Please let me know.

Thanks,

swb1

 

[melone]

PLL

 

[swb1]

Do you have a part that you can suggest?? The PLLs that I have saw have even divides like 2, 4, 6, 8, 12.

Thanks,

swb1

 

[VEBill]

2 separate oscillators would probably be simpler. A PLL circuit will inevitably involve more components (since oscillators are often just one).

The PLL approach would be to divide the 64 MHz by two repeatedly (2^6) to make 1 MHz as the reference. The PLL oscillator would oscillate at 33 MHz, and a sample of that would be divided by 33 (a tiny bit tricky) and phase locked to the reference. Since it is a fixed frequency (?), the loop parameters should be simple to work out.

Sometimes designers will aim for twice the desired frequency and divided by two as the last step to precisely even-up the duty-cycle.

 

[VEBill]

Hmmm... Another option would be to generate 2112 (the LCM, not the Rush album) MHz and divide down. Probably too high to be practical.

 

[oldfieldguy]

Generate 11 MHz and pass filter the second and third harmonic.

old field guy

 

[VEBill]

What's the 22MHz for?

 

[swb1]

Cypress makes a programmable clock generator (CY22381) that will seem to work.

swb1