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LMX2571EVM: LMX2571- PLL SETTLING TIME

CAREY
Prodigy 150 points

Part Number: LMX2571EVM
Other Parts Discussed in Thread: LMX2571

Hello Team,

We been using FSK_SPI mode.  2FSK and we are sending 0xAA.

if we add bit duration of 200us (means we are sending bit every 200us) we are able to see the two deviation peaks in spectrum analyser.

if bit duration is less than 50, through carrier is locked, but FSK modulation is not visible properly in spectrum analyser. another peaks coming between desired two peaks . seem not to be like 2fsk 

do LMX2571 need some PLL settling time to move to that deviated frequency ?

Regards,

CJI

  • 0
    TI__Guru** 122190 points

    Hi There,

    It could be a measurement issue. Try changing the RBW, VBW and sweep time, etc in the spectrum analyzer.

    Also make sure the PLL loop bandwidth is wide enough to accept higher modulation frequency.