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PMP31202: The reason for shunt current sensing prepared on circuit

Guru 19605 points
Part Number: PMP31202
Other Parts Discussed in Thread: PMP31210

PMP31202 is high power board and need even a little reduce power consumption.

I think that current sense is better to set only inductor DCR sensing to reduce power consumption. 

Please let me know about the background for shunt current sensing prepared on reference design: PMP31202. 

And, what is the advantage to use shunt current sensing more than inductor DCR sensing?

Best regards,

Satoshi

  • Hello Satoshi-san,

    if you look at my schematics you could see that the circuit and my PCB is prepared for both options, shunt sensing or DCR sensing.
    But windings tolerances result in impact on power sharing of the four phases.
    Pure resistive sensing results in best power sharing in between the power stages !

    So I accepted some minor additional mW losses in such a 800W+ design, still achieving effcy 98%;
    please check temperature measurement and see the sharing, pics are better than all my words...

    But you can get selected inductors from magnetic vendors, DCR tolerance 5% only - by accepting some additional cost.

    fyi, PMP31210 is my modification to input voltage range 18V to 58V, best regards, Bernd

  • Hi Bernd

    Thank you for reply,

    I understood the mean of current sensing that you designed.

    By the way, is spread spectrum have any impact for performance of power sharing?

    I concern that PMP31202 and PMP31210 are setting DITH connect to AVDD, spread spectrum disabled. 

    I guess that no spread spectrum become the best power sharing in between the power stages.

    Best regards,

    Satoshi

  • Hello Satoshi-san,

    spread spectrum does not impact the power sharing, it's peak current mode control.
    I don't need spread spectrum because I try to make a reasonable layout, and,
    so I avoid AF modulation of the output voltage.

    Hope this helps & best regards, Bernd