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bq24610 100% duty and refresh pulse

Nam, Dino
Expert 6305 points

Dear Expert,

After adding snubber circuit at switch node( 2.2nF and 2 ohm), 100%duty and refresh pulse waveform(absebse if battery) is changed. please let me know your opinion about below waveform.

Why this waveform is changed? Is there any side effect because below waveform? Please review below waveform

<before adding snubber circuit and absence battery>

 

<after adding snubber circuit and absence battery>

 

Please let me know if you need more information.

Thank you.

  • 0
    TI__Genius 11480 points

    Hi,

    If I am understanding this correctly, these are the waveforms of the switch node before and after adding a RC snubber at the switch node (not the output).

    If that is the case, it looks like there is quite a bit of ringing at your switch node. Adding your snubber slowed down the frequency of the oscillations (increasing the RC time constant), which we see in your second set of waveforms. Could I see your high drive, low drive,switch node, and if possible your inductor current waveforms before and after your snubber?

  • 0 in reply to David Wiest Jr
    TI__Genius 11480 points
    Hi,

    Looking into this a bit further, it looks like your inductor is operating in DCM for some reason during the battery detection scheme. Could I possibly see a schematic with component values? Also, waveforms of SRN, PH, and VCC would be helpful. Thanks!
  • 0 in reply to David Wiest Jr
    TI__Expert 6305 points
    Hi,

    Thank you for your support.
    The reason of adding snubber, there is EMC issue during charging battery, so we added snubber circuit. After Battery insertion, charging and other function is operated well. But we concern side effect because of different waveform from datasheet when battery is removed. Please let me knwo your opinion about side effect.

    - When battery is removed, waveform is different from datasheet. If battery is removed, we can show waveform of 100% duty and refresh pulse(datasheet 13page) is it right?

    After checking other waveform, I will update soon. but customer schematic is confidential. I can't update customer schematic because of external forum. so please let me know your mail address.

    Thank you.
  • 0 in reply to Nam, Dino
    TI__Genius 11480 points

    Hi,

    Those supporting waveforms will be helpful if figuring out if there are any harmful side effects. Have they tested to see if the circuit functions properly during precharge, constant current, and constant voltage? 

    The waveform worries me a little, but we can dig deeper. Do you know what was causing the EMC issues?

    You can reach me at d-wiest@ti.com

  • 0 in reply to David Wiest Jr
    TI__Expert 6305 points
    Hi,

    I sent waveform and schematic by e-mail. please review and let me know your opinion about side effect.

    Thank you.