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BQ24171: External schottky diode from SW node to ground question

Paul Yeh
Genius 14365 points
Part Number: BQ24171

Hi

why this part needs external schottky diode from SW node to ground? As I know we already had L/S MOSFET embedded.

Please advise.

can we remove it?

Thanks

  • 0
    TI__Genius 11790 points
    Dear Paul,

    Discussed with team, the schottky diode is to prevent the GND influenced by high current. At charging current>2A application, when the high side FET turn-off and ready to turn-on the low side FET, there would be a high current go through the low side FET and influence the GND level. And then it will cause the accuracy worse. You can refer to electrical table, current regulation portion. Accuracy is set with using the schottky diode.
    So if we remove it, it maybe influences the accuracy.

    Best regards,
    Ann Lien
  • 0 in reply to Ann_Lien
    TI__Genius 14365 points

    Dear Ann,

    Thanks

  • 0 in reply to Paul Yeh
    TI__Expert 6170 points
    Hi Ann,
    Any guideline to choose the Schottky diode?

    Regards,
    Allan
  • 0 in reply to Allan Fan
    TI__Genius 14365 points

    Hi Allan,

    I think you can use EVM board suggested part-B220A-13-F (Schottky diode-2A-20V) for design.

    In our EVM board specification, you can see we can support charge curent up to 4A.

    This schottky diode purpose is (1) To replace L/S MOSFET body diode condution (2) To reduce ground noise as well.

    So I think you just consider this diode's pulse current value is enough or not.

    BTw, below table is our EVM board recommended operation conditions.

    Paul

    Thanks