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BQ24171:Behavior when USB2.0 (500mA) is connected when ISET is set to 2A.

okashita.ikki
Prodigy 100 points
Part Number: BQ24171

Tool/software:

If a user accidentally connects a USB 2.0 (500mA) device while the ISET is set to 2A for USB 3.0 (3A), what are the possible effects?

USB2.0 side: voltage drop? Or will it be destroyed?
BQ24171 side: charging time will slow down, but the charging operation itself will continue?

  • +1
    TI__Guru**** 166916 points

    Hi Okashita,

    The charger will attempt to pull the full 2A.  5V USB2.0 output will droop below the charger's UVLO of 3.6V typical  but likely not be destroyed.   If the voltage droops below UVLO, the charger turns off.  There will likely be an oscillation of power up, droop, powerup, etc.  Just curious why you are using BQ24171 in a USB 1S application when we have other 1S chargers with D+/D- pins and VINDPM that would not have this issue?

    Regards,

    Jeff

  • 0 in reply to Jeff F
    Prodigy 100 points

    Thank you for your response.
    We are using BQ24171 due to limitations imposed by the specification.

    Best regards,

    Okashita