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DRV8432 pin connections question

Gehan Manuel
Prodigy 195 points

Hi,

I have a coule of questions regarding the pin connections of the above chip.

1. Is it possible to set the Roc_adj value by the use of two TPL0501-100 connected in rheostat mode like shown in the figure ?

2. Is it possible using a R2R connection (figure below) to convert the FAULT and OTW signals to an analog value and read it using a microcontroller ADC ? 

3. Is it possible to use electrolytics as bootstrap capacitors and if so to which pins should I connect the positive and negative leads?

4. The voltage rating for the bootstrap capacitors are mentioned as 100V. Can I use a lower value and if so is there some way of assuming the voltage rating ?

5. How much current does the IC need in the 12V rail (to power the GVDD and VDD). Is it possible to use a 7812 chip?

Best regards 

  • 0
    TI__Mastermind 26065 points

    Hi Gehan

    Please refer to my comments below.

    1. Digital pot should be fine. Any particular reason that you want a full scale variable OC adjustment range?

    2. I know your propose but nOTW and nfault are OD pins. You need pull up the pins and have some modification on your current structure.

    3. Non-polar Cap is recommended. Since the value needed is small, why you want electrolytic one?

    4. 100v is to meet the MAX PVDD needs and give proper margin which is important for motor driver application. If your PVDD is lower, the cap rating can be lowered too. but I guess there are not too much options here as the cap usually have 100v, 65v, and 65v is too low maybe.

    5. Our EVM has a 1.5A regulator. 7812 has a lot of current rating types. Please use ones have the abillity to ~1.5A.

    Thanks.

    Wilson

    Motor Application Team 

  • 0 in reply to Wilson Zuo
    Prodigy 195 points

    Hi Wilson thank you for your reply.

    I want to use digital pots so the current limits can be set in software.

    The electrolytics are because I am finding it a little hard to obtain 100V ceramic SMD caps. 

    I will use a 7812 with the appropriate ratings.

    Best regards

  • 0 in reply to Gehan Manuel
    TI__Guru 55615 points

    Gehan,

    One correction to the previous post.

    On your question regarding bootstrap, it is OK to use 25V.  Basically, you will only see the GVDD voltage (12V nominal) across this cap.  16V cap is a little tight, so that is why I recommend 25V as the next standard and readily available ceramic capacitor.

     

  • 0 in reply to Ryan Kehr
    Prodigy 195 points

    Hi Ryan Kehr,


    Thank you very much for your reply. It was very helpful and brought much relief to me. I can do better because I have 50V ceramic caps.


    I have another question, I will be connecting the ground pin of the  TPL0501-100 to the GND_X of the DRV8432. Will this be a problem as one of the digital pot's pins is  already connected to AGND ? 


    Best regards.