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design advice: capacitors on G_VDD pin on DRV8412

lemarchand olivier
Intellectual 270 points
Other Parts Discussed in Thread: DRV8412

Hi,

 

I need to implement 5 DRV8412 in a layout, I would like some advice on capacitor to use on G_Vdd pin.

is one 100µF enough on 12V for all modules or do I need to put one capacitor for each module and what value is needed?

 

thanks for your help,

Olivier 

  • TI__Mastermind 21805 points

    Olivier,

    I suggest a 1uF cap near all four of the GVDD pins for each device, also have a 1uF and 47uF cap near the pin of VDD. 

    Using a single device, the suggested application uses one 330uF capacitor on GVDD, so I do not think 100uF would be enough for all five. Depending on how you route PVDD on your layout, you should probably just have one 330uF cap per device.

    Thanks,

    Matt

  • in reply to Matt Hein
    TI__Guru 55655 points

    Olivier,

    As Matt mentions, 1uF capacitors on all GVDD pins and 47uF on EACH VDD is good. 

    In terms of current requirements, the TOTAL (GVDD+VDD) current from 12V for each IC is low at room temperature (~50mA).  However, under heavy loads and higher temperatures, the current into the VDD pin can increase quite significantly due to substrate collection by the 12V guard rings in the device. 

    For this reason, we recommend designing the 12V power supply with curent capability at least 5-10% your rated load current and no less than 100mA.  This is PER device.  So, in your case you would multiply by 5. 

    Please make sure to take this into account in your design.

     

  • in reply to Ryan Kehr
    Prodigy 30 points

    Thanks Ryan and Matt,

    I'm working with Olivier on the same project.

    To be more precise, all GVDD pins are connected to 12V and all VDD pins to 3V3.

    All GVDD pins are decoupled by 1µF and more by one 330µF per device.


    First question, is-it possible to decrease from 330µF down to 100µF per device (knowing that the devices side by side)?


    Next, all VDD pins are decoupled by 100nF and 47µF per device.

    Second question, is-it possible to decrease from the 47µF down to 10µF per device (knowing that the devices side by side, too)?


    thanks a lot for your help,

    Arnaud

  • in reply to Arnaud SIMON
    TI__Guru 55655 points

    Arnaud,

    There must be some confusion. 

    VDD = GVDD = 12V.  VDD should NOT be connected to anything other than 12V.  Or to be more specific, the recommended range is 10.8V - 13.2V.

    I would recommend keeping the large decoupling, 100uF, close to the VDD pin and 1uF capacitors on EACH GVDD pin.  VDD should also have a small 0.1uF or 1uF capacitor as well. 

    Please see figure 13 in the datasheet.

     

  • in reply to Ryan Kehr
    Prodigy 30 points

    Ryan,

    In the rush, we have not corrected all of our previous electronic board.
    Thanks to you, we will avoid an error of copper.

    Now we are less in the fog.

    big thank you,

    Arnaud