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LMG1020: Nanosecond pulse generation problem in LMG1020

Hungli33
Prodigy 60 points
Part Number: LMG1020

Dear Sir / Madam,

I need to generate a short pulse for LMG1020 and I use the recommendation method from data sheet to use IN+ and IN- for the nanosecond pulse generation (see the following)

but I test in my prototype and found trigger pulse happened in both rising and falling edge (see the following)

Is there any suggestion on this problem?

  • 0
    TI__Expert 4070 points

    Hi Hungli,

    Thanks for reaching out!  

    You may need to increase your IN- signal on-time (duty cycle) to ensure that it is staying on longer than the IN+ signal.  If this does not help, could you please provide an oscilloscope capture that is zoomed in to the input signals to see the overlap better?

    You could also do the opposite and decrease the on time (duty cycle) of the IN+ signal.

    You could also shift the IN- signal more to the right (more of a delay shift); but this will increase your output on-time.

    I hope this helps and answers your question.  If so, please press the green button, otherwise feel free to follow up!

    Thanks!

    Aaron Grgurich

  • 0 in reply to Aaron Grgurich
    Prodigy 60 points

    Aaron,

    Thanks for your reply, 

    I share you the zoom in picture in 2 edges (Yellow trace is IN+, Blue trace is IN-, Green trace is output of LMG1020 and purple trace is Voltage across GaN FET.

     

  • +1 in reply to Hungli33
    TI__Expert 4070 points

    Hi Hungli,

    This is what I was thinking would be the case.  The blue trace, IN- goes low too soon, therefore turning the output on.

    To fix this, you will need to increase the Duty Cycle of the IN- signal, or in other words, have it stay on longer.

    Referencing this truth table from the datasheet may help too:

    This should fix your issue.  If so, please press the green button, otherwise please feel free to follow up!

    Thanks,

    Aaron Grgurich