LMK04828: Clock Configuration File

Hi Nireeksha,

Based on clocking block diagram architecture, both 245.76MHz and 156.25MHz clocks out are not possible. Both frequencies least common multiplication factor is 3840GHz, which is way beyond the internal VCO frequency range. 

Also can you confirm on the external VCXO frequency, is it 122.8MHz or 122.88MHz?

If you have 156.25MHz CLKin0 input frequency and VCXO frequency is 122.88MHz, attached is the updated config file for 245.76MHz DCLK and 7.68MHz SYSREF frequencies FYR.

LMK04828_156.25MCLKin0_122.88MVCXO_245.76MDCLK_7.68MSYSREF.tcs

Thanks!

Regards,

Ajeet Pal

Hi Nireeksha,

Here, again the additional frequencies 100MHz, 27MHz, 52MHz  and 125MHz can't be possible with 245.76MHz clock generation. You need to adjust the other frequencies, which could generates with the same VCO frequency (2457.6MHz) and integer divider values. Also the odd clocks out can have SYSREF out frequency or same as device clock. e.g. CLKout8 and CLKout9 can have only same frequencies or CLKout9 can have SYSREF outputs.

Thanks!

Regards,

Ajeet Pal

Hi Nireeksha,

The other frequencies can be generated with the integer VCO frequency, which is not possible with the 122.88MHz VCXO frequency. 

To have these, you need to change the VCXO frequency to integer value (100M / 50M etc..), with that internal VCO frequency can be integer and can generate all required frequencies except 245.76MHz and it can be changed to 250MHz or so.

You can play with TICS Pro tool for your required frequencies and change the VCXO frequency.

Thanks!

Regards,

Ajeet Pal

Hi Nireeksha,

Ok. Least common multiplication factor of the 100M, 27M, 54M & 125M frequencies is 13.5GHz, which is not covering with the internal VCO frequency. You need to have output frequencies which can be generated with the common VCO frequency and integer division. say 100M, 25M, 50M and 125M.

LMK04828 doesn't support DCLK divider value above 32, so the minimum output frequency would be ~74M (VCO0 min freq - 2370M, div - 32; 2370/32=~74M), except SYSREF frequency. Hence, I would be suggesting LMK04832, which is pin compatible of LMK04828 and have higher channel divider value. LMK04832 configuration file attached here FYR.

 LMK04832_DualPLL_100MCLKin0_100MVCXO_2500MVCO.tcs

Thanks!

Regards,

Ajeet Pal

Hi Nireeksha,

I am afraid to say, you can't be having all above required frequencies from single selected VCO frequency with integer dividers.

You need to change the few frequencies, those can be generate from same VCO frequency.

Thanks!

Regards,

Ajeet Pal