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LMX2571: FSK_SPI Hold time issue

CAREY
Prodigy 140 points

Part Number: LMX2571

Hello Team,

we want to tramit data using FSK_SPI. for 2FSK

here is my RF spec

FSK rate: 28.8 kbps
Deviation: ±24 kHz
SPI: 6.75 MHz
Symbol period: 35 µs -- this is the holdingtime, adding as delay after R34 register Writing.

if we adding more delay like 1ms. am able to see the the two peaks between deviation in spectrum analyser.

but i cannot add more than 35us , where am not able to see the distinct peaks it is like below.
image.png



Regards

CJI

  • 0
    TI__Guru** 120130 points

    Hi There,

    I don't see any reason why the wait time needs to be >1ms. Programming of R34 only take 3.7µs, you have more than 30µs until programming the next R34. 

    For example, in below plot, the interval between programming R34 is 22.22µs. 

    This is my test setup.