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TPS2546: TPS2546 charge current to Apple iPad device

Randy Chen
Intellectual 2295 points
Part Number: TPS2546

Hi,
Customer needs a explanation for the TPS2546 charging Apple iPad device behavior. Why the charge current get higher when Vbus voltage raise up from 4.87V to 5.13V? Is this behavior tying with Apple iPad device such as iPad measured the Vbus voltage and determined the charge current?

  • 0
    TI__Expert 3075 points
    Randy,
    That is quite possible, even likely. Charging algorithms are considered sensitive IP by mobile device makers since it directly relates to battery life and, therefore, customer satisfaction. A typical algorithm will consider Battery voltage, % charge, temp., age, number of times drain to 0V, number of times overcharged, and the supply voltage.
    A simple test would be to set VIN to 4.87 V and then measure (VIN-VOUT) across the 2546 using a DVM. Divide that result by the measured current and the answer should be 70 - 100 mOhms. If it is, then we know the 2546 is fully on and the battery charger just isn't pulling the current.
  • 0
    TI__Intellectual 1920 points
    Hi Randy,

    I believe it may be the IPad's charging algorithm but as Jim said we do not know for sure. Another quick check you could do is connecting a different device to the port and changing VBus from 4.87V to 5.13V to make sure it's the IPad and not the board itself. Could you send waveforms of VBus, D+, D-, and the current through VBus?

    Thanks,
    Donovan
  • 0 in reply to Donovan Porter
    TI__Genius 10370 points
    Hi Randy,

    Thanks again for using our parts. I'm going to close this thread since it's been a couple of weeks without any activity. But feel free to re-open this thread if you're still having issues with this part. And you can always start a new thread if you encounter other issues. Thanks for using TI parts in your design.