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LM22677 Noise

HUNGH WABER
Prodigy 20 points
Other Parts Discussed in Thread: LM22677

I used your company's LM22677 as the first level of voltage processing (5V output), but I found that when it starts, it will cause my image to have oblique ripples

The I observed that when the LM22677 was started, the power output was Ripple instead of horizontal, and the amplitude was about 450mV, and there was a phenomenon of ground bounce.
What should I do?

  • 0
    TI__Mastermind 40040 points
    Hello Hungh,

    How are you measuring the ripple? You should make sure you have a short ground lead. Use a spring clip across around the Gnd portion of the scope probe barrel and measure directly across C37. Also you may want to consider using a decoupling capacitor by your load. Use 100nF and a 10nF very close to your load and re measure directly across the 10nF as described above.

    Hope this helps?

    David.
  • 0 in reply to David Baba
    Prodigy 20 points

    Hi David

    Yes,I have a short ground lead,and my load (TDA2EG) have many decoupling capacitor,but the problem still exists.

  • 0 in reply to HUNGH WABER
    TI__Mastermind 40040 points

    Hello Hungh,

    Are you using a spring clip and measuring across a 10nF cap or smaller? Also would be good to measure the noise with the Switch waveform to make sure that the Switch node is the source of the issues?

    If so, you may want to look at the self resonance of the inductor you are using?  You should make sure that this very low inter winding capacitance.

    Hope this helps?

    David.