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SM72295: SM72295 with isolated signal and power supplies

user5987970
Prodigy 10 points
Part Number: SM72295

Hi there,

That's my first message on this forum.

I'm designing a motor control board based on the SM72295 gate driver.

My board is powered with two isolated supplies : dirty 50V supply for the motor, and a clean 12V for the embedded µC.
As the SM72295 requires 12V and 3.3V, my idea is to use the clean 12V power for that purpose, and use 50V for the power stage, but my grounds are isolated, and I'm not sure that I can keep them isolated (even if I don't need to have a high isolation level: 100V max).

Is that possible to design such board with isolated grounds based on a SM72295?

Regards,

Léo

  • 0
    TI__Mastermind 23215 points

    Hello Leo,

    Thank you for the interest in the SM72295 driver. For the SM72295 VDD and VCCA and VCCB, you can use an LDO to generate the 3.3V to 5V for VDD from the 12V you have available for VCCA and VCCB.

    Regarding the isolation from the 12V bias supply and the 50V power stage supply, the SM72295 is a dual half bridge driver which has the input ground reference and the low side driver ground reference the same. The easiest implementation would be to have a common ground for the 12V bias and the 50V power input voltage.

    Otherwise you could have separate grounds, but you would have to have all of the control input signals and output signals isolated with one of TI's available digital isolators. Also you would have to then provide the bias voltages for the SM72295 from the 50V ground referenced side,  from the 50V power input supply.

    Do you have the option of connecting the 12V supply ground and the 50V power train input ground together in your design?

    Please confirm if this answers your questions, or you can post additional questions on this thread.

    Regards,

    Richard Herring