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TPS5450: Ringing noise issues

Pradeep N52
Prodigy 190 points
Part Number: TPS5450

We are using TPS5450 in our design due to Ringing noise issues we added snubber and also 10E resistor in series with bootstrap capacitor to increase the rise time. After adding snubber we got better results but still it's not enough as recommended in other question we added 10E resistor in series with bootstrap capacitor. The high frequency harmonics reduced but low frequency noise is increasing attached captured graphs for reference. Is increasing the rise time affects inductor charging/discharging characters?? attached ckt also for reference.

  • 0
    TI__Mastermind 23845 points
    Hi,

    Yes a slight increase rise time will not change the overall operation of the device. There might be a slight reduction in the efficiency.
    I would recommend start with 3.3 ohm, 4.7 ohm and work your way up to 10ohm.

    Thanks
  • 0 in reply to Arief Hernadi
    Prodigy 190 points
    HI,
    thanks for your reply ... I have another small query why the low frequency sine component generated after adding 10E series resistor?? if you observe last graph instead of steady line ringing it generated low frequency component at 10MHz rang. Is this because of inductor charging and discharging wasn't proper or Resistor limiting the current or Power rating of resistor or too much increase in the rise time affect in any other way?/..... I want to know the reason ...
    Waiting for your valuable reply...
    Thanks & Regards,
    Pradeep
  • 0 in reply to Pradeep N52
    TI__Guru 73585 points
    It is difficult to say exactly the cause of the 10MHz ring. It could be parasitics on the components or the layout.
    It could also be an artifact of the probing technique.
  • 0 in reply to Frank De Stasi
    Prodigy 190 points

    Hi,
    I though inductor charging discharging may be affecting this.. So i can ignore the point that inductor is causing this problem right??

    Also another small query, Is radiation depends on Electric field intensity??

    also at particular frequency range say 100MHz, if we have 10 cycles of ringing noise(sine wave) and after tuning it becomes less that is let's say 4 cycles.and amplitude remains same for both waveforms.... 2nd one giving better response in frequency domain for me. i want confirmation that i am tuning in proper way to reduce the noise before proceeding further ..... Please help on this

    attached some waveforms for your reference.Please analyze the graphs and let me know your inputs.

    Regards,

    Pradeep

  • 0 in reply to Pradeep N52
    TI__Guru 73585 points
    I think that the parasitics of the inductor may contribute to ringing.
    I you are able to tune your design to minimize the EMI you are interested in then I think you are on the right track.
  • 0 in reply to Frank De Stasi
    Prodigy 190 points
    Is there any possible way to completely reduce the noise ... ???We are getting small ringing about 100mV wrt to overshoot and undershoot of switching waveforms. Output ripple is 50mV.. Can we reduce the ringing fully so that out is uniform with maximum 50mV ripple... Please give us all possible option with respect to above regulator to suppress the noise... Mention any extra components if needed...we need clean output...
    will share the layout also if you want
    Regards,
    Pradeep
  • 0 in reply to Pradeep N52
    TI__Mastermind 23845 points
    Hi,

    Could you also try to use a ferrite bead with a high impedance at 100MHz?
    Here is some information about reducing the output voltage ripple
    www.ti.com/.../slyt740.pdf

    Thanks