LMX2615-SP: The method to remove spurious

EUNSUK KWAK

Part Number: LMX2615-SP
Other Parts Discussed in Thread: LMX2582

I'm using LMX2615-SP IC for 2GHz output.

Our frequency is 2228.20, 2228.25 MHz. But these frequency has spurious near an operation frequency.

I tried to several method using TICS Pro bool to get better result. But I got similar results.

I think my setting values for resistors have some problem. Please let me know the proper setting values to solve the problem.

I want to remove them.

I got the result waveform and setting value as below.

Thank you,

Best regards

over 5 years ago

0 Noel Fung over 5 years ago

TI__Guru* 93670 points

Hi Eunsuk,

Looks like 16.384MHz is not a very good choice, with this reference clock frequency, I expect spurs at 156kHz, 4kHz, 2kHz and 26kHz. Some of these spurs are crosstalk spurs and the rest are fractional spurs.

Crosstalk spurs is related to the reference clock frequency, so these spurs can be eliminated with a different reference clock frequency, for example, 17MHz.

2kHz and 4kHz fractional spurs can be eliminated if we change fractional DEN to, say, 1000001.

0 EUNSUK KWAK over 5 years ago in reply to Noel Fung

Prodigy 50 points

Hi Noel Fung,

Thank you for your respond.

I agree with your opinion that we need to change the reference frequency.

How do you expect spurs frequency??? Do you have a calculation for spurious frequency???

Maybe output frequency can be changed, not fixed.

Thank you,

Best regards

Kwak

0 Noel Fung over 5 years ago in reply to EUNSUK KWAK

TI__Guru* 93670 points

Hi Eunsuk,

Yes, crosstalk spurs and fractional spurs frequencies can be figured out. Please read LMX2582 datasheet, section 8 for details.

0 EUNSUK KWAK over 5 years ago in reply to Noel Fung

Prodigy 50 points

Thank you for your help.

It was a big help.

Clock & timing

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LMX2615-SP: The method to remove spurious