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TPS40428: Current Accuracy with CSD95378BQ5M

John Fedak
Expert 6715 points
Part Number: TPS40428
Other Parts Discussed in Thread: CSD95378BQ5M

Hi Team,

My customer is looking at implementing the TPS40428 for a 60A 1V design.

They have tested out the TPS40428 EVM with the CSD95378BQ5M and are seeing that the current calibration is not very accurate (going through TI Fusion GUI). For instance, they are seeing at the bottom range a current of 1.5A going through the system, when 0A is reported.

I do see an Iout cal offset in the Fusion GUI, is this recommended to use? Do we have any collateral on best practices for this?

At the top range, (over 30A) - would accuracy be in the range of +/- 3%?

Thank you!

Regards,

~John

  • 0
    TI__Mastermind 24075 points

    Hi John,

    The current readout error is mainly caused by input offset of current sense amplifiler. This input offset does not change much when load current increase.

    On TPS40428 datasheet page 8 spec table, when Iout (per phase) is larger than 20A, the maximum current readout error is +/-640mA.

    There may be additional error from power stage (CSD95378B) side, but with 30A per phase current, the total +/-3% error is a reasonable estimate.

    Thanks

    Qian

  • 0 in reply to Qian Chen
    TI__Expert 6715 points
    Hi Qian,

    Great to hear on the +/-3%.

    Thank you for the feedback, is the best way to deal with this input offset error with the Iout offset in the Fusion GUI?
    Would you expect that offset to vary across devices? (In other words, would this need to be calibrated for every board?)

    Regards,
    ~John
  • 0 in reply to John Fedak
    TI__Mastermind 24075 points
    Hi John,

    Yes, the Iout offset in PMBus (Fusion GUI) can be used to deal with the input offset error.
    Due to process vairation, the offset varies part to part, so it needs to be calibrated for every board.

    Thanks
    Qian