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Original question:

DRV8889-Q1: Capacitor on VCP pin

DRV8889-Q1: how to calculation charge pump capacitor value

HB ZHANG
Prodigy 50 points
Part Number: DRV8889-Q1

Hello team

        from datasheet, CPH-CPL capacitor  value suggestion that 22nF ,and C(VCP) =220nF;

could you explain to how to calculation the two capacitor value?   we want to know that what's effect by change the two cap  value.

an example: C(VCP)  is 220nF ,and CPH-CPL is 33nF.

Thank  you!

  • 0
    TI__Guru 55605 points

    Hello!

    There is no easy calculation.  

    Load transient behavior of CP voltage depends on the VCP-VM cap.  Load regulation depends on CPH-CPL fly cap.

    Up to 47nF can be considered for better load regulation.  22nF, 220nF are suggested in datasheet for decent performance for given size/cost of the caps. Going higher than 47x to like 68x starst affecting the charging times these fly cap & bulk cap take, so >47nF is NOT recommended.

    C(VCP)  is 220nF ,and CPH-CPL is 33nF.   <--  This combination would be OK!

    Regards,

    Ryan