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How to isolate the MCU properly?

Kash Olia
Genius 3215 points
Other Parts Discussed in Thread: SN74LVC2G07

Hi,

It might be a very general question, but what's the best isolator IC to isolate the MCU from motor driver circuit. I would like to have some sort of isolation between the PWM signals and motor drive circuit. Does SN74LVC2G07 isolator fast enough to transfer PWM signals? any other suggestions?

Thanks,

  • 0
    TI__Mastermind 24485 points
    Hello,

    Are you simply trying to isolate the digital supply from the analog supply?
    SN74LVC2G07 would work on a very simple level since its just an open drain output FET, but I would have some concerns.

    What supply you are putting on the output as the pullup?
    How much current does this supply need to source during motor drive operation?
    What kind of motor are you driving? We have other devices which may be much more suitable for your application and accept digital inputs to protect the MCU from inductive kickback

    Best,
    Michael
  • 0 in reply to Michael J Schultis
    Genius 3215 points

    Michael,

    I'm going to control two PN half H-Bridges (BTS7960B):

    Although the datasheet says BTS7960B can be connected directly to MCU, but I prefer to use isolator between. 

    It's not supposed to draw current on PWM pins since it only drives the MOSFET.

    I need to control two PWM signals, two ENABLE signals and read two ADC signals so I want to make sure that I have a proper isolation between BTS7960B and the MCU.

    Thanks,

  • 0 in reply to Kash Olia
    TI__Mastermind 24485 points
    Hello Kash,

    If you are concerned about the MCU direct connection to the half bridges and want an added layer of buffering, the SN74LVC2G07 would work fine since its driving high impedance input pins anyway, just make sure to not exceed the output voltage rating of the device.
    Not sure what frequencies you are working at, but this device can do 10s of MHz which I am sure is way more than what you need for this application.

    Best,
    Michael