LMX2571: why phase noise is unstable?

Harry Ma

Intellectual 1970 points

Part Number: LMX2571

Hi Team

As following video shows, the phase noise looks unstable when it output 150MHz.Fosc=19.8M, Fpd=4.8M. Could you tell the possible reasons why this happen?

over 1 year ago

0 Noel Fung over 1 year ago

TI__Guru* 90560 points

Hi Harry,

Could you provide your PLL configuration?

0 user4852208 over 1 year ago

Prodigy 140 points

Hi Harry,

This measurement is misconfigured.

The instrument range is 250M-7GHz.

+1 Noel Fung over 1 year ago in reply to user4852208

TI__Guru* 90560 points

Hi Harry,

OK, can we close this post?

0 Harry Ma over 1 year ago in reply to Noel Fung

TI__Intellectual 1970 points

Hi Noel

we adjust the measurement. but it is still unstable. the following is the configuration.

Can you help to check why this happen?

0 Noel Fung over 1 year ago in reply to Harry Ma

TI__Guru* 90560 points

Hi Harry,

Are you using internal or external VCO?

0 Harry Ma over 1 year ago in reply to Noel Fung

TI__Intellectual 1970 points

EXTERNAL VCO

0 Noel Fung over 1 year ago in reply to Harry Ma

TI__Guru* 90560 points

Hi Harry,

Try below configuration.

externalvco.tcs

Clock & timing

Clock & timing forum

LMX2571: why phase noise is unstable?