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PMP9766: Question on large current condition

Satoshi
Guru 19685 points

Part Number: PMP9766
Other Parts Discussed in Thread: TPS552882, TPS25940

I considering backup solution on 5Vmain / 6A, 300ms backup time condition based on PMP9766.

(Buck-Boost IC will change TPS552882, VCF: 4.75V)

Please let me know about two points below for PMP9766 solution;

①I guess that  timing for change Vmain to buck boost Vout have a few delay and collision, design guide and zoomed image is below.

　・When collision time become long , is there any problem or careful points?

　　If problem, please let me know any measure. (Is disconnect FET add to TPS552882 Vout side (between R6 to C4), effective?)

　・How long assuming below Figure 6 timing?

　　　　

②When Vmain drop and change buck-boost output to Vsys, should TPS25940A set disable or not?

　If should to disable, I plan to set Vmain less than VCF = less than UVLO threshold by add voltage divider, is it correct?

Best regards,

Satoshi

  • 0
    Guru 19685 points

    Any update on this?

  • 0
    TI__Intellectual 1525 points

    Hello Satoshi,

    unless you don't need 6A supplied from Vmain, you need to change the eFuse as well, since the TPS25940 can't handle 6A.
    The maximuim current this IC can handle uinder worst case conditions is 4.78A.

    A suitable replacement for short bursts of high currents would be https://www.ti.com/product/TPS25947

    Regarding your first question:
    The backup converter is enabled all the time, therefore, as soon as Vmain drops below the output set point of this converter, the output voltage will not drop any further. This happens basically without delay. The only thing that may be delayed in this design is the switchover of the operation mode of the converter. The reverse blocking capability of the eFuse will ensure, that no current flows back to Vmain.

    This also answers your second question: due to the automatic reverse current protection, there is no need to disable the eFuse.

    I hope this answers your questions.

    Best regards,
    Björn