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LAUNCHXL-F28377S + TIDM-DC-DC-BUCK SFRA Results

David Kirakosyan
Prodigy 10 points
Other Parts Discussed in Thread: BOOSTXL-BUCKCONV, TIDM-DC-DC-BUCK, SFRA

Hi,

We are working with the TI F28377S Launchpad (LAUNCHXL-F28377S) connected to the C2000 DPS BoosterPack (BOOSTXL-BUCKCONV):

https://www.ti.com/tool/BOOSTXL-BUCKCONV#3

 According to the  Reference Designs: TIDM-DC-DC-BUCK manual on p.29, in “Lab 1: Open-Loop Check for VMC”  Magnitude of Plant (LC filter supposed) > 0dB, in range of frequencies much lower than resonant point (100-1000kHz).

https://www.ti.com/lit/ug/spruhz5a/spruhz5a.pdf?ts=1602847109672&ref_url=https%253A%252F%252Fwww.google.com%252F

 

So, we discovered information about C2000_DPSWorkshop by following link: https://processors.wiki.ti.com/index.php/C2000_DPSWorkshop

In comparison with C2000 DPS Workshop EVM in  User's Guide about C200 SFRA in “Figure 25. Plant Frequency Response Plot” on p.43 Magnitude of Plant < 0dB.

https://www.ti.com/lit/ug/spruhz5a/spruhz5a.pdf?ts=1602847109672&ref_url=https%253A%252F%252Fwww.google.com%252F

We understand negative value of gain on low frequencies because of LC filter, Rds, current sensing and other active loads in manual for C2000 DPS Workshop EVM board, but in our case, working with C2000 DPS BoosterPack we have gain 1.78dB, what is over 0. How you can explain this effect?

 

Best Regards,

David

  • 0
    TI__Guru 62975 points

    David,

    The inputs to SFRA are typically in the form of Per-Unit (PU) values, which are normally bounded between 0 and 1.  The absolute values that are represented by the PU values will scale with the gain of the sense circuits from the plant.  The differences in component values between the Workshop hardware and BoosterPack hardware may explain the difference.

    -Tommy