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UC3843A: UC3843A

Luis Alvarez2
Prodigy 20 points
Part Number: UC3843A

Hello

Ive designed a mosfet driver using a UC3843A. Have ramp oscilations100kHz at pin 4 but no oscilations at output pin 6, can you help

  • 0
    TI__Expert 6080 points

    Hello,

    If the Turn-on threshold of 9V on Vcc is met. I cannot think of any other reason why there is no gate pulses at the output. IS the VREF pin coming up to 5V? It could be possible that the IC got damaged.

    It would be helpful to see the schematic, what are the Rt and Ct values that have set your frequency to 100kHz?

    Regards,

    Sonal

  • 0 in reply to Sonal Singh
    Prodigy 20 points

    Hi Sonal

    Vcc is 12V, VREF is 4.95V. May it be possible that IC gets damaged on startup?. Rt is 1k5 and Ct 6n4, I send you the Schematic.

    Regards

    Luis400V Boost Converter.rar

  • 0 in reply to Luis Alvarez2
    TI__Expert 6080 points

    Hi Luis,

    Please make sure that your schematic matches the typical application example in the datasheet of UC3843A. For example, the CVref is missing, CVdd cap of 100uF is pretty large: you may be better off using a smaller cap ideally it should be 10 times the gate capacitance of the main switching FET. I would strongly recommend comparing your schematic against the "Typical Applications" under section 8 of the datasheet.

    Regards,

    Sonal

  • 0 in reply to Sonal Singh
    TI__Expert 6080 points

    Hello Luis,

    Since I have not heard back from you, I am assuming that you were able to resolve the issue. I will proceed to close this thread now.

    Regards,

    Sonal