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BQ24610: BQ24610 damage components in battery pack

Mobydata - Tony Liu
Intellectual 265 points
Part Number: BQ24610

Hi,

we use the BQ24610 for battery charger base product,

but we find there is a strange behavior on the charger IC, please help check the test waveform in the attached file.

and we also find the large current from battery to charger IC during the battery insertionBQ24610 design.pdfBQ24610 design.pdf

  • 0
    Intellectual 265 points

    when battery is not connected with the charger IC circuit, find there is voltage drops on VBAT, if at this time, the battery is insert, the battery voltage is higher than charger IC output voltage, the large current shall happen

  • 0 in reply to Mobydata - Tony Liu
    TI__Mastermind 25800 points
    Hey Tony,

    To me this looks like inrush current into the capacitors of the charge controller's output LC tank. Based on your description, it seems like the worst of the inrush current is during the low period of battery detection as described in section 9.3.23 Battery Detection of the datasheet. The low point is shown in Figure 17 when the battery voltage causes VFB to fall below the VLOWV threshold.

    This is considered normal behavior during any plug in event.

    To see if the behavior is the same without the charger, try pre-biasing 30-uF of ceramic capacitance to 3V and then apply your battery and monitor the voltage and current.


    Regards,
    Joel H
  • 0 in reply to Joel Hernandez II
    Intellectual 265 points

    Hi Joel,

    what does "pre-biasing 30-uF of ceramic capacitance to 3V" mean?

     the 3V is FB pin?

    and there is another question:sometime, we find that the VBAT pin is about 0.8V when battery is not attached. you can check that in my test waveform.

    Note: in my 1st waveform, there is CH, name is VCORE, that actually is VBAT,

    BRS,

    TONY L

  • 0 in reply to Mobydata - Tony Liu
    TI__Mastermind 25800 points
    Hey Tony,

    My thought process was to have you measure the inrush current and consequently the voltage drop when apply your battery to some capacitors that already have 3V across them. By pre-biasing, I meant for you to apply 3V across some ceramic capacitors that are isolated/external to your system and board.

    As far as VBAT going down to 0.8V in your first waveform, to me this looks like a completely discharged capacitor being charged up.


    Regards,
    Joel
  • 0 in reply to Joel Hernandez II
    Intellectual 265 points

    Hi Joel,

         After Chinese Holiday, I will check the inrush current after the prebias added.

         To see if the behavior is the same without the charger, try hipre-biasing 30-uF of ceramic capacitance to 3V and then apply your battery and monitor the voltage and current

    >> we found that on some boards, the VBAT is 0.8V as battery is not attached, and after the battery is attached, the charging can't work well.

    BRS,

    TONY LIU

  • 0 in reply to Mobydata - Tony Liu
    TI__Mastermind 25800 points
    Hey Tony,

    Can you take a waveform showing the SRN voltage while the battery is disconnected? I imagine this is related to the battery detection algorithm but we can see it if the time scale is long enough (about 500ms/div to 1s/div).


    Regards,
    Joel H
  • 0 in reply to Joel Hernandez II
    Intellectual 265 points

    Hi Joel ,

       please check the below captured waveform(no prebias 3V added), we find that some time VBAT voltage is not so high. 

  • 0 in reply to Joel Hernandez II
    Intellectual 265 points

    Hi Joel ， 

    when the adapter is not attached, the test waveform can be found as below, the inrush current is so high. is there any soution suggested for so large inrush current? tks a lot in advance!

    we also test the inrush current on your EVM board without power adatper attached, please check the below:

    BRS,

    TONY LIU

  • 0 in reply to Mobydata - Tony Liu
    TI__Mastermind 25800 points
    Hey Tony,

    VSRN (VBAT) collapsing is due to the battery detection circuitry. It pulled current from SRN to discharge the node and pushes current into the SRN to charge the node. If the node moves, the charger detects that there is no battery present. This is why you see the voltage dip.

    As far as the inrush current, again I will say this is due to the capacitors on the board. You have 30uF of output capacitance. The EVM has double the capacitance (including the 40uF of capacitance on the input rail that the battery will always see). So you see double the current.


    Regards,
    Joel H
  • 0 in reply to Joel Hernandez II
    Intellectual 265 points

    Hi Joel,

     so this voltage dip 0.8V is reasonaable, correct?

     I add the LDO 3.3V voltage on the VBAT, after this work arroud is added, the inrush current can be reduced down. please help review the attached file. tks a lot!

     but we still don't know how to resolve the inrush issue as the adapter is not attached.

    Battery Inrush Current 2019-0212 - 副本.pptx

    BRS,

    TONY LIU

  • 0 in reply to Mobydata - Tony Liu
    TI__Mastermind 25800 points
    Hey Tony,

    The inrush current happens for two reasons. The main reason is the capacitance, and you will find this on any design you ever do.

    The second reason is because this charger has battery detection. With battery detection, the output capacitors are forced to charge and discharge. When the battery is plugged in when the capacitors are fully discharged, the inrush current will be fairly high.

    Your workaround seems okay to me as it forces the charger to see a fixed voltage (effectively battery always present). However, you may want to consider a current limiting switch such as load switch with a programmable current limit.


    Regards,
    Joel H
  • 0 in reply to Joel Hernandez II
    Intellectual 265 points

    Hi Joel,

    tks a lot for your support,

    I compare our shcematic with your EVM schematic, we find that there is a mistake, we don't add the 0.1uF capacotor on the SRP,

    is there any risk? will this missing capacitor cause malfunction on charging, or only impact the current  accuracy?

    BRS,

    TONY LIU

  • 0 in reply to Mobydata - Tony Liu
    TI__Mastermind 25800 points
    Hey Tony,

    We recommend that capacitor to provide common mode filtering in order to preserve signal integrity for the ICHG and VBATREG regulation.


    Regards,
    Joel H