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UCC21520EVM-286: OUTA and OUTB Too Slow

TI-CSC
Genius 12835 points
Part Number: UCC21520EVM-286

Tool/software:

Hello E2E Experts,

Good day.

We have acquired the UCC21520EVM-286 driver, and upon using it, we have not been able to achieve the results shown in its user guide. The pulses are being activated; however, the rise time is too slow. I have attached an oscilloscope image to illustrate this.

The delay between the input pulse and the MOSFET activation is as expected, but the rise time of OUTA or OUTB is too slow—approximately 50 ns—which is significantly higher than what's indicated in the user guide.

I would like to know if there is any configuration we might be missing or if this could be an issue with the evaluation board.

Regards,

TICSC

  • 0
    TI__Expert 8686 points

    Hi,

    Thanks for reaching out with this question.

    The longer rise and fall times on the EVM are due to the 10ohm external gate resistors connected to the outputs of the gate driver.

    The datasheet specifications for rise and fall times are measured with 0ohm external gate resistors.

    With these resistors shorted, the measurements should better match the datasheet.

    Regards,

    Hiroki

  • 0 in reply to Hiroki Honda
    TI__Genius 12835 points

    Hello Hiroki,

    The gate output resistor was replaced; however, the rise time still seems high. I'm attaching an image with the results of this test. The test was also performed with a MOSFET connected to the gate, a test that I also attach below.

    I hope you can help me, as the rise time is noticeably longer than what your tests indicate.

    Regards,

    TICSC

  • 0 in reply to TI-CSC
    TI__Expert 8686 points

    With a MOSFET load connected, it would be expected for the output rise/fall times to be slower due to the MOSFET's input capacitance and intrinsic gate resistance as well as the VDD voltage value which would affect the expected peak current values.

    With this all considered, if the setup is identical to the EVM and datasheet test conditions, the rise/fall times of the gate driver output should match the datasheet specifications.

    Hope this helps.

    Regards,

    Hiroki