LMX2592EVM: Spur on all channels on EVM.

Jonathan Kolbrak

Part Number: LMX2582EVM
Other Parts Discussed in Thread: USB2ANY, LMX2592EVM

I'm running an LMX2582EVM around 5.2 GHz and seeing a 4.2 MHz spur on all channels despite the charge pump setting, external power supplies, even if the Num/Div dividers are set to an integer channel, disconnecting the USB2ANY the spur is there. The modified loop filter components are a passive second order with C1=3.3nF, C2=100nF, R2=680ohms. I can send the register dump in an email about this setup. Anyone have any other ideas what is causing this or seen this spur?

over 7 years ago

0 Jonathan Kolbrak over 7 years ago

Intellectual 470 points

The title should say LMX2582EVM not LMX2592EVM

0 Brian Wang over 7 years ago in reply to Jonathan Kolbrak

TI__Expert 7935 points

Hi John,

I tried this out, same settings. You have a clean integer mode settings, and that spur has nothing to do with Fpd. I tried with a clean siggen, no spurs, and then a pulse generator which I get 300kHz offset spurs at around -70dBc. Try changing your input reference source to see if we can isolate the source. You can also use the on-board XO which is 100MHz, but can be a good comparison check.

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LMX2592EVM: Spur on all channels on EVM.