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LP87702-Q1: Harmonics

Mitchell
Expert 4915 points
Part Number: LP87702-Q1
Other Parts Discussed in Thread: LP87702, AWR1843, AWR1843BOOST, MMWAVE-STUDIO

Hi Team,

My customer is seeing the harmonics of the LP87702 (4MHZ) causing some false positives to the AWR1843 radar data, so they are considering enabling spread spectrum to reduce the peak of this harmonics. Do we happen to have any spectrum analyzer data (with and without spread spectrum) that they could compare to?

They are going to capture some datapoints from the AWR1843BOOST EVM reference board as a baseline to debug this issue. However, they'd like to know if we fully characterized all the power supplies on these reference boards? If we have some data, can you please send them over? 

Thanks,
Mitchell

  • 0
    TI__Expert 8730 points

    Hi Mitchell,

    Switching frequency spur shows up on Radar FFT if noise filtering (2nd stage LC filter) is not sufficient or due to some layout related couplings. Increasing output capacitors also helps to reduce the ripple noise. If you can send me (email me) their schematics and layout, I am happy to review it and provide the feedback.

    Spread spectrum should also help to reduce the spurs to some extent. I am not very sure whether AWR1843BOOST board is directly setup to enable the internal spread spectrum of LP87702 through MMWAVE-STUDIO interface. They may have to hookup LP87702 EVM USB interface to the LP87702 device on AWR1843BOOST EVM and enable the spread spectrum through LP87702 GUI. May be it is faster to enable the spread spectrum on their board through their software. In general, AWR1843 board has been validated, but without spread spectrum enable.

    Regards,

    Murthy

  • 0 in reply to Krishnamurthy Hegde
    TI__Expert 8730 points

    Hi Mitchell,

    I see that you have contacted us through email and shall we close this E2E thread?

    Regards,

    Murthy