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BQ24753: Ringing noise at battery charging circuit

Pradeep N52
Prodigy 190 points
Part Number: BQ24753

Dear,

We are using the below attached circuit in our design.The Ringing noise is observed at TP49 which is about 300mV(Battery charging voltage). after that we try to increase the rise time of the switching circuit so R559 and R568 resistor changed to 10E. The noise is reduced but still not up to the mark. Currently we are observing about 140-160 mV of noise at TP49 this should be reduced below 100mV. The circuit attached below please give all possible ways to reduce the noise further.. Is increasing the rise time by mounting higher resistance value helps to address this issue? We are worried increasing the rise time may affect the performance. Please let us know any modification would you like to recommend.

Regards,

Pradeep

  • 0
    TI__Guru*** 143950 points
    What is the frequency of the ringing? Is it the same as the buck switching converter? Is it sinusoidal or triangular?
  • 0 in reply to Jeff F
    Prodigy 190 points

    It's sinusoidal wave of frequency about 100 MHz during positive peak of switching. The waveform also attached. We try to increase the rise time by adding 10E resistor for R559 and R568 , Now the noise is about 160mV sinusoidal wave . we should reduce this to below 100mV.

    TP49 Battery_Pack+ with R568 and R559 with 0E Resistor

    Waveform measure at L1 switching side(Green) with TP49 Battery_Pack+(Yellow). R568 and R559 with 10E Resistor

  • 0 in reply to Pradeep N52
    TI__Guru*** 143950 points
    How are you measuring the ripple on BAT? Does the voltage probe have a long ground lead or are you using the a ground pigtail and measuring directly across the capacitor on BAT? How tight is the layout for the FETs and C132 and C403? Can you a small 0.1uF capacitor from drain of high side FET to ground of low side FET?