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DRV8811 Charge pump flying capacitor

Walter Rota
Prodigy 20 points

Hi,

my question is about choosing capacitor between CP1 and CP2.  I'm wondering if 220nf is mandatory or not. In the latter, how do i choose it?

Operating condition are +24V supply, 600mA / winding, full step, no acceleration.

I've tried different values e.g 100nf and even 10nf without a noticeable reduction in the performance

Looking forward to hearing from you

Regards

  • 0
    TI__Intellectual 1100 points

    This is a little bit difficult to answer, since all of our testing and characterization has been done using the 220nF capacitor.  So we cannot guarantee proper operation with smaller capacitors.

    That said, I am not surprised that the part functions correctly with smaller capacitors.  Many of our other parts which have a similar architecture use a 10nF flying capacitor.

    If you are willing to do enough testing to satisfy yourself that all is well, you may be able to use a smaller capacitor.  I would suggest measuring the voltage on the VCP pin during all phases of operation, temperature, load, and supply voltage.  The VCP voltage should not drop below VM + 10V.