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TIDA-00447: Decoupling capacitors C16, C17, C18

John Pan
Intellectual 990 points
Part Number: TIDA-00447

Hi, I have a question on decoupling capacitors' connection. In TIDA-00447 design reference Figure 4, decoupling capacitors C16, C17, and C18 were connected from VM to M1-SL. I am wondering why these decoupling capacitors are not connected from VM to GND directly. I believe direct connecting these capacitors to GND will decouple better. Could you please explain why they were connected to M1-SL instead of GND?

Thanks,

John

  • 0
    TI__Prodigy 420 points

    Hi John,

    I agree with you, but right now I cannot get the comments from the original designer of this reference design.

    I think the possible reasons should be:

    1) For such low-voltage and high-current application, normally the shunt resistors are very small (both R and L), there is no obvious difference between these two connections.

    2) In some cases, the shunt resistors are far away from the low-side MOS, it is hard to place the decoupling capacitor across the VM and GND.

    Above is just my understanding, for your reference.

    Felix