LMX2592: Clock & timing forum

singam vamshi krishna

Part Number: LMX2592

Hi team. With the help of Pllatinum sim tool I can predict the output phase noise with respect to loop bandwidth. But I am interested in knowing the effect of reference phase noise on output RF signal phase noise.

I would like to see the effect of reference phase noise on output.

As per theoretical calculations I consider Output phase noise = Phase Noise (Ref) + 20log(Fout/Fref), but I want it through simulation. However I have entered the value of reference frequency phase noise at different offsets in Pllatinum sim tool but there is no change in output phase noise PLL.

over 3 years ago

0 Ajeet Pal over 3 years ago

TI__Genius 12560 points

Hi Singam,

You can include the reference (source) phase noise response in PLLatinum sim tool and it will show the source effect on the LMX2592 output.

Thanks!

Regards,

Ajeet Pal

0 singam vamshi krishna over 3 years ago in reply to Ajeet Pal

Intellectual 775 points

I agree, But that doesn't has any effect on output phase noise. I have entered worst phase noise knowingly but there is no change in output phase noise. for -130dBc/Hz it has same output and for -70dBc/Hz also the same. Could you please show me the variation.

Thank you for your patience time.

0 Ajeet Pal over 3 years ago in reply to singam vamshi krishna

TI__Genius 12560 points

Hi Singam,

You could try to change on all field or can load the data also with the PN at multiple points of reference input signal.

Here, I am attaching the example of Pllatinum sim file FYR, where you can play with changing PN of REF @10kHz and see the response.

https://e2e.ti.com/cfs-file/__key/communityserver-discussions-components-files/48/LMX2592_5F00_sim.sim

Below are the plots for 2 PN points of REF at 10kHz offset and see the variation.

Hope, it clarifies your queries.

Thanks!

Regards,

Ajeet Pal

0 singam vamshi krishna over 3 years ago in reply to Ajeet Pal

Intellectual 775 points

Thanks for that. But I can't see any significant change in output frequency phase noise even if I increase the reference frequency phase noise drastically from -140dBc/Hz to -80dBc/Hz

0 Ajeet Pal over 3 years ago in reply to singam vamshi krishna

TI__Genius 12560 points

After changing the PN, you need to press on "Update OSC Matrics" to see the effect.

Regards,

Ajeet Pal