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DRV8806: some questions about the DRV8806 CLAMP configuration

Frank Xiao
Genius 12055 points
Part Number: DRV8806

Hi team,

My customer wants to evaluate the DRV8806 in the system. The structure is below. The green side is the board. The Vm is powered by the board 24v. The inductor pull up side is connected to another 24v. The other side of the inductor connect to the OUT x . How to consider the CLAMP pin configuration,( for we cannot see the inductor pull up 24v on the board)? Whether we can connect to Vm? How to decide how many cap we need for the VM in case the Vm voltage goes up? Thanks. 

  • 0
    TI__Mastermind 37683 points

    Hi Frank,

    Thank you for posting to the motor drives forum.

    I have a question. Is the 24 supply on the board powering the driver and 24V supply connected to the inductive load outside the board the same? Are both supplies coming from one main power supply?

    Assuming both supplies are the same, you can configure the set-up as shown below where a bulk capacitor and 0.1µF capacitor is placed near the VM pin of the driver without adding another capacitor on VCLAMP pin. If my assumption is wrong please let me know.

  • 0 in reply to Pablo Armet
    TI__Genius 12055 points

    Hi Pablo,

    The two suppliers are not the same. Not from one main power supply. That's why i proposed to use the cap at Vclamp only. BTW: HOW TO decide the cap value? Thanks.

  • 0 in reply to Frank Xiao
    TI__Mastermind 37683 points

    Hi Frank,

    If that's the case then I suggest placing the cap on VCLAMP as well. In terms of the actual value, I suggest choosing 0.1µF for both the VM on the board and the external VM. The 0.1µF capacitor is the recommended value on the datasheet but you can change it. Typically, you want to choose a capacitor value that can suppress the transients and noise that is expected in your system. For example, if you expect very high frequency noise, you might want to choose a lower capacitance value. 0.1µF is a good starting point and you can always change if there is still noise in the system.

    A bulk capacitor should be placed in both VM lines to stabilize and clean up each VM signal. 

    I hope this answers your question.