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DRV8432 & 12V Supply Current

Penn Linder
Expert 1035 points
Other Parts Discussed in Thread: TPS7A4001

The datasheet of the DRV8432 seems to indicate that the 12V supply needs to provide IVDD of 12mA, and IGVDD_X 8mA typical.  This means the 12V supply requires at least 44mA (12mA + 4 x 8mA).

I would really like to use the TI TPS7A4001 voltage regulator to generate the 12V - it will keep my power supply simple and small.  I don't need 12V for anything else.  The datahseet for the TPS7A4001 specifies a maximum current of 50mA.  Will this regulator provide enough current for the DRV8432?

 

  • TI__Guru 55615 points

    Good question and I am glad you asked.

    The total supply current at 25C ambient temperature will be <50mA as you suggested and your regulator choice will be OK.  However, the current could increase significantly when the device junction  temperature goes too high (above 125C) for example under heavy load conditions.  This extra current will flow on the VDD pin due to substrate current collection by 12V guard rings. 

    So, it is recommended to design the 12V power supply with current capability at least 5-10% of your load current and no less than 100mA to assure stable device performance across temperature. 

  • in reply to Ryan Kehr
    Expert 1035 points

    I'll have to think it through some, but needing to supply 700mA (10% of 7A) at 12V is almost a design killer for me.

    The datasheet says that the "12-V supply should be from a low-noise, low-output-impedance voltage regulator".  Can you please put some meat on those bones for me?  What noise level and impedance level are low enough?

    It seems like a TI reference design that derives the 12V supply from the 48V supply would be of great benefit to your customers (at least to this customer!).

     

     

     

  • in reply to Penn Linder
    TI__Guru 55615 points

    Ivek,

    Please check out the DRV8412-C2-Kit reference circuit attached.  We use a 12V buck on the EVM now and that works just fine.  Not exactly low-noise. 

    10% is conservative and assuming 125C junction temperature.  If you have adequate heat sinking, you will never see these temperatures in your design.  You can target 5% and be OK.

    4152.DRV8412EVM_RevG-Schematic.pdf