LMX2572LP: Spurious with MASH

David Park

Expert 6890 points

Part Number: LMX2572LP

Tool/software:

Hi,

The setting is as below.

spur is as below.

In the graph, Fout%Fosc is 12MHz offset. is it correct? not 26.4MHz?

Thanks.

over 1 year ago

+1 Dean Banerjee over 1 year ago

TI__Mastermind 28031 points

Yes, you are correct. This should be the distance to the closest integer boundary. We could claim that this 410.4 MHz is 26.4 MHz away from a multiple of 38.4 MHz, but it is also 12 MHz from an integer multiple. So it should choose the 12 MHz.

I'm updating the PLLatinum Sim to include oscillators, so I'll fix this, but likely this will go out in December.

0 David Park over 1 year ago in reply to Dean Banerjee

TI__Expert 6890 points

Hi Dean,

Thanks for your answer.

In the graph, 12MHz is highest.

I confused if 12MHz spur is highest or 26.4MHz spur is highest.

Which is highest among Fout%Fosc and integer multiple?

Thanks.

0 Noel Fung over 1 year ago in reply to David Park

TI__Guru** 112000 points

Hi David,

The simulation predict 12Mhz spurs is -130dBm, which is super small. At 26.4MHz, it is expected that the level will be even smaller.

Actual measurement does not see any spurs at 26.4MHz offset.

Clock & timing

Clock & timing forum

LMX2572LP: Spurious with MASH