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TMS320F28031: TMS320F28031 cannot pass GB18655 test

Part Number: TMS320F28031

Recently, when we tested the EMC of a 28031PAQG product, we found that in GB18655 conducted disturbance current test item, 55Mhz and 72Mhz frequency points exceeded the standard. When positioning, only the DSP is powered on, but the signals of these two frequency points are still high. The subsequent use of the spectrometer to directly scan and confirm that they are sent from the DSP, and the data of the spectrometer is consistent with the data frequency points of the current method. And in the state of DSP reset, the over standard frequency points still exist, although the radiation intensity and bandwidth are reduced. See the figure below for the strongest position of the over standard frequency point and the data of the spectrometer,

We would like to know if there are any modules in the DSP whose working frequency is related to these two frequency points (similar to or divisible), or if the corresponding frequency can be changed or other means can be avoided, so as to help our rectification.

  • Are you able to provide more details on exactly how this test is done? You could share any photos/videos with me privately. 

    By “Spectrometer” , I presume you are referring to a near-field probe connected to a Spectrum Analyzer. Please try this experiment: Power-down the flash and run some code from RAM and repeat the measurement.