• State Resolved
  • Locked Locked
  • Replies 7 replies
  • Answers 2 answers
  • Subscribers 63 subscribers
  • Views 564 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

BQ25886: CAN YOU PLEASE VERIFY THIS DESIGN

SYED ALI NAJEEM
Prodigy 130 points
Part Number: BQ25886
Other Parts Discussed in Thread: BQ25798

Hi,

Can you please verify this 2S battery charging design?

I am using this device along with BQ296100. Thus the SYS pin gets affected by this IC?

  • 0
    TI__Guru**** 167196 points

    HI Syed,

    I don't see any obvious issues on the schematic.  I couldn't read the resistor values.  This device is very sensitive to input line inductance.  I recommend increasing VBUS capacitance to 4.7uF and PMID capacitance to 22uF.

    Regards,

    Jeff

  • 0 in reply to Jeff F
    Prodigy 130 points

    Hi,

    Thanks for the reply. I have modified those changes.

    Here are a few questions:

    I have shorted the D+ and D- with a 100-ohm resistor. Is it okay or do I need to short directly?

    I have connected the load to SYS pin (The load avg current is 2.5A and max current is 4A). Is it okay? does BQ296100 affects the functionality of SYS pin?

  • 0 in reply to SYED ALI NAJEEM
    TI__Guru**** 167196 points

    Hi Syed,

    BQ296100 is a pack protector and so should not load SYS.  It is okay to use a 100 ohm resistor to short D+/D-.

    The BQ25886 max battery (and therefore SYS) output current is only 2.2A. It will not be able to provide the 2.5A avg and 4A max without supplementing from the battery.  This means the battery will likely never charge.  I recommend changing to BQ25798.

    Regards,

    Jeff

  • 0 in reply to Jeff F
    Prodigy 130 points

    Hi,

    We don't want any communication interface. That's why we chose this IC. 

    Is it okay to leave the SYS floating and connect the battery directly to the load?

  • 0 in reply to SYED ALI NAJEEM
    TI__Guru**** 167196 points

    Hi Syed,

    It is not recommended to do that but again, the max output current is 2.2A and your system needs 2.5A avg and 4.5A max so I don't think the battery will ever charge.

    Regards,

    Jeff

  • 0 in reply to Jeff F
    Prodigy 130 points

    Hi,

    Thanks again. 

    Here are few follow up questions:

    1. What if we don’t need the power path? Can we just connect the load to the battery? Also, the device will be completely off while charging so load current consumption will be in milliamps  

    2. If no, then is there any other way to charge 2S battery with 5V USB Supply?

  • +1 in reply to SYED ALI NAJEEM
    TI__Guru**** 167196 points

    Hi Syed,

    Regarding 1, not recommended but since there is no load while charging, I see no issue with tying the load to BAT or to SYS.

    Regarding 2, BQ2588x is TI's only 5V to 2S LiIon charger.

    Regards,

    Jeff