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Original question:

BQ24780S: BQ24780S charger IC

BQ24780S: Charge current of BQ24780S

Lumina Gui
Expert 2635 points
Part Number: BQ24780S

Hi Sir,

Our notebook project using BQ24780S for battery charging. From the datasheet we know that the maximum charging current can up to 8A. 

However, when we setting the charge current to 5A, the actual charge current is only 4.1A.We also tried to set the charging current to 6A but the actual charging current is still to 4.1A. So we want to know the reason of this problem and how to set up the charging current to 6A or more.

Thanks,

Best Regards

  • 0
    TI__Genius 11385 points

    Hi Lumina,

    Thanks for reaching out.

    1. How are you adjusting the charge current? The charge current setting is the lower of ChargeCurrent() register setting and ILIM pin setting on bq24780S. Please check the ILIM pin setting as well.

    2. If number 1 doesn't work, can you share your input voltage, battery voltage, and load current?

    3. Can you share your register values as well?

    Thanks and I hope this helps,

    Peng

    *Please press "This Resolved My Issue" on the thread if my answer is satisfactory

  • 0 in reply to Pengzhao Zhu
    Expert 2635 points

    Hi Peng,

    The answer for your question is as follows:

    1) How are you adjusting the charge current? The charge current setting is the lower of ChargeCurrent() register setting and ILIM pin setting on bq24780S. Please check the ILIM pin setting as well.

           RE: battery charge current= 5000MA, charger voltage = 8.7V

    2) If number 1 doesn't work, can you share your input voltage, battery voltage, and load current?

            RE: adapter input current= 3200MA, input voltage = 19V

    3)  Can you share your register values as well?

            RE: CHGR_ChargerOption(0x12) = 0x8108; 

                   CHGR_ChargeOption1(0x3b) = 0xCE00;

                   CHGR_ChargeOption2(0x38) = 0x0384;

                   CHGR_ChargeOption3(0x37) = 0x9C40;

                   CHGR_ChargeProchotOption0(0x3C) = 0x4A70;

                   CHGR_ChargeProchotOption1(0x3D) = 0x5900; 

    Thanks,

    Best Regards

  • 0 in reply to Lumina Gui
    TI__Genius 11385 points

    Hi Lumina,

    Have they check if the ILIM pin is limiting the charge current? Try changing 0x38 register to 0x0304 which should change the settings so that the charge/discharge current limit is set by the registers only.



    By the way, the registers you gave me doesn't have the full register map.

    We also have the EVM for them to compare the difference between their system and a working design.

    https://www.ti.com/tool/BQ24780SEVM-583 

    Thanks and I hope this helps,

    Peng

    *Please press "This Resolved My Issue" on the thread if my answer is satisfactory

  • 0 in reply to Pengzhao Zhu
    TI__Genius 11385 points

    Hi Lumina,

    It has been a week since the last response. There were not any replies from you so I assumed this problem is resolved.

    If you have more questions, feel free to start a new thread and reach back to us on the TI E2E forum.

    Thanks and I hope this helps,

    Peng

    *Please press "This Resolved My Issue" on the thread if my answer is satisfactory