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TPS92691: Schematic Check

Victor Chen_HK
Expert 5130 points
Part Number: TPS92691

Hello,

Could you please help to check my customer's schematic using TPS92691 as a buck-boost LED driver?

  • Input voltage 9.5V to 30V from battery
  • LED voltage 24V
  • LED current 2.1A

The inductor in actual circuit is 100uH. IC switching frequency is around 84Khz.

Thanks and best regards,

Victor

  • 0
    TI__Mastermind 28655 points
    Hello Victor,

    Looks like the LED current sense resistors will give 2.095A
    The peak current sense looks to be at 35A which seems high, .525V/(0.06 ohm/4)
    Css, C63, is 1000 pF might be too small
    Fsw appears to be around 84 KHz with 100 Kohm
    Inductor ripple current seems reasonable

    Regards,
  • 0 in reply to Irwin Nederbragt
    TI__Expert 5130 points

    Hi Irwin,

    Thanks for your suggestions.

    With the above schematic, the actual switching frequency is around 37kHz and the overshoot voltage is more than 20V. See waveform below.

     However, after they changed the inductor to 22uH, the switching frequency and voltage spike are back to normal. But for this thread, I think we can take it as resolved.

    Thanks and best regards,

    Victor