• State TI Thinks Resolved
  • Locked Locked
  • Replies 4 replies
  • Answers 1 answer
  • Subscribers 64 subscribers
  • Views 2673 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

ISO5852S: Isolated Mosfet driver dsat connection for AC

VBKen
Intellectual 255 points
Part Number: ISO5852S

I am designing a circuit to control an AC load using back to back Mosfets as shown in the attached diagram. 

The circuit shows the connection of the DESAT pin in what would normally be a DC circuit.  This would only protect the Mosfets for half of the AC cycle.  I have sketched in a second resistor and diode (dotted lines) to look after the the other half of the AC waveform however this connects the DESAT below GND and may not work. 

Can anyone please suggest a way to connect the DSAT pin so that it will properly protect the Mosfets from short-circuits over both halves of the AC bus cycle?

Thanks, Ken

  • 0
    TI__Expert 4875 points

    Hi Ken,

    I'm not too familiar with this configuration. At first glance, you may need to implement a secondary form of SC protection in order to protect both FETs, such as a shunt resistor method. But I will do some looking into this and will get back to you with a recommendation. 

    Regards,

    Audrey

  • 0
    TI__Mastermind 23055 points

    Hello Ken,

    I have contacted the expert on this device and they will get back with you shortly.

    DSAT normally works with the expectation that the drain voltage transitions positive relative to the driver ground reference. In this case the lower side drain voltage would go negative to indicate a dsat fault. If that is the case, this connection may not work.

    I will let the engineer more familiar with the ISO5852S comment when she is back in the office.

    Regards,

  • 0 in reply to Richard Herring
    Intellectual 255 points

    Thanks Richard, I have not been able to figure this out yet, so any help would be appreciated.

    Best regards,

    Ken

  • 0 in reply to VBKen
    TI__Expert 4875 points

    Hi Ken,

    Please check out this application report and this TI Design which I believe will help you with your application. I have not seen the DESAT circuit used in this way, and typically have seen these types of bidirectional switch configurations controlled via two separate drivers.

    Regards,

    Audrey