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Original question:

BQ25895: Device Revision

BQ25895M: PMID boost mode efficiency with PFM

Steve Fenwick1
Prodigy 250 points
Part Number: BQ25895M
Other Parts Discussed in Thread: BQ25895

One of the features of the BQ25895M over the BQ25895 is PFM mode for the boost converter, to improve low-load efficiency.

However, I don't see any reflection of this in the BQ25895M data sheet; the boost mode efficiency plots for the two parts look identical.

Please comment.

Best,

Steve

  • 0
    TI__Mastermind 21575 points

    Hi Steve, 

    The reason the boost efficiency plot does not change is because PFM mode for boost converter operation is included on both the BQ25895 and BQ25895M. The new feature on the M version is that PFM for boost mode can be enabled/disabled via REG0A. On the original BQ25895 PFM mode for boost converter cannot be disabled. 

    Therefore there is no boost mode efficiency improvement on the BQ25895M compared to the BQ25895 only the option to turn off PFM, which would reduce the efficiency at light loads. 

    I hope my comments clear up the confusion.

    Best Regards,

    Garrett 

  • 0 in reply to Garrett Kreger
    Prodigy 250 points

    So the plots shown already reflect use of the PFM mode at light loads? In that case, I would have expected the -M version to have a plot showing efficiency with PFM disabled.

    Thanks!

    Steve

  • 0 in reply to Steve Fenwick1
    TI__Mastermind 21575 points

    Hi Steve, 

    Correct, the plots shown already reflect PFM mode being enabled at light loads.

    Steve Fenwick1 said:
    I would have expected the -M version to have a plot showing efficiency with PFM disabled.

    Thank you for the feedback. Unfortunately we do not have such a plot available at this time. You can expect the efficiency to roughly follow the trend I have drawn in the image below. 

    I am also happy to perform efficiency testing on the BQ25895MEVM with PFM disabled at a specific load current and battery voltage you are interested in operating at.  Just let me know.

    Best Regards,

    Garrett