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BQ25619: Battery Charger Read Status

Siburaj D S
Prodigy 105 points
Part Number: BQ25619

Hi TI Team,

I am facing issue while configuring the battery charger BQ25619(Part No: BQ25619RTWT) in host mode. In default mode I am getting the correct status outputs in Status pin. But while configuring in host mode I am getting below values from the Charger Status 0 register (Address - 0x08).

1. Without Battery Connected - Status register value changing. The register values showing are 0x34 and 0x3C(Varying periodically).

2. With Battery Connected in Charging state. The values showing is always same 0x34.

3. With Battery Connected in Fully Charger state. The value showing is always same 0x3C. 

I am getting expected values CHRG_STATUS[1] and CHRG_STATUS[0] only for 2nd and 3rd case.

Can you check and share the reason why the CHRG_STATUS[1] and CHRG_STATUS[0] is not showing as 00 when battery is not connected. ?

Regards,

Siburaj D.S.

  • 0
    TI__Mastermind 31260 points

    Hello Siburaj D.S.,

    The charge status register will not show 00 when no battery is connected because the charger views the output capacitor on BAT as a small battery. Please refer to the link below for a FAQ post with more details on why the charge status periodically changes from fast charge to charge termination when no battery is connected. 

    FAQ BQ25619 operation with no battery connected 

    CHRG_STATUS on REG08 will indicate 00 (not charging) when charging is disabled. 

    Regards,

    Garrett

  • 0 in reply to Garrett Kreger
    Prodigy 105 points

    Hi Garrett,

    Thanks for your reply. Can you share your responses for below queries also ?

    1. In host mode is it possible to identify battery connected or not with the charger ? If possible how can we check the status ?

    2. In host mode is it possible to detect the battery charging state, fully charged state state ? If possible how can we check status ?

    Expecting your immediate reply.

    Thanks & Regards,

    Siburaj D.S.

  • 0 in reply to Siburaj D S
    TI__Mastermind 31260 points

    Hi Siburaj D.S.,

    1) No, the charger IC does not have a way to detect the battery connection status. As the FAQ mentions when no battery is connected the device will attempt to charge the output capacitor as if it were a battery. 

    2) In host mode the status register you mention above CHRG_STAT (REG08 bits [3:4]) will detect the battery charging state unless there is no battery connected. 

    Regards,

    Garrett 

  • +1 in reply to Garrett Kreger
    Prodigy 105 points

    Hi Garett,

    1. If I remove the capacitor connected from the battery point(Pin 14/13) whether the battery charger will work properly. What is the purpose of this capacitor ?

    2. Whether it will read not charging status when capacitor is not connected 

    Thanks & Regards,

    Siburaj D.S.

  • 0 in reply to Siburaj D S
    TI__Mastermind 31260 points

    Hi Siburaj D.S., 

    1) The device will not work properly if the output capacitor is removed. The purpose of said capacitor at the BAT pin is to absorb output switching ripple voltage/current so the IC can provide constant current for fast charge and constant voltage for voltage regulation. 

    2) I do not believe removing the capacitor will result in a status read of not charging from REG08.  The description of "00 - Not Charging" on page 41 of the datasheet is potentially misleading. CHRG_STAT = 00 when charge is disabled (section 8.3.6.1 of D/S shown below) To prevent the device from going through the stages of charging, termination, discharge then repeat disable charging when the battery is removed. 

    Best Regards,

    Garrett