• State
  • Locked Locked
  • Replies 7 replies
  • Subscribers 63 subscribers
  • Views 1851 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.

BQ24133: Switching between BATDRV mode and normal mode

Brian Wengreen
Prodigy 70 points
Part Number: BQ24133

Hello TI,

We have used the BQ24133 in previous designs and it has worked well.  However, we are bringing up a new PCB design and are encountering some unknown issues.  Here is our problem:

Application:

15V AC adapter -> BQ24133 -> 16V Boost regulator -> Smart Home Speaker (with large in-rush current during power up)

Battery pack: 12V, 3S1P

When the smart home speaker is connected to our circuit, the in-rush current is very large so the BATDRV pin automatically connects the battery to the input of the 16V boost (i.e. the speaker) to provide additional power.  After the power up event, the additional current is no longer needed so the BQ24133 goes back into charging mode.  

In our mass production design (that works) you can see the scope shot below that shows the BATDRV pin (blue) and the input to the 16V boost regulator (yellow) in the moment that the boost regulator is gated on through a power FET and the smart speaker starts to power on.

In this image, you can see the BATDRV pin (yellow) and the BQ24133 SW pin (blue) in a zoomed out time scale.  When we gate on the 16V boost regulator and power up the speaker, you can see that the charger stops switching and then restarts.  We seen the BQ24133 STAT LED go off and then back on, seemingly in sync with the SW pin.  We don't know why the STAT pin is going off or why the charger starts to switch again.  However, the application works fine this way.

In our new PCB design, that is a very similar schematic, we see the BATDRV pin engage, the SW pin stop, but then the SW pin never restarts.  The STAT LED just continues to blink until we power cycle the input.  This a show stopper in our application.  When the speaker is turned on, we need the BQ24133 to continue charging, not get stuck in a fault mode.

This image is the same setup as the one above, but uses our new PCB design (yellow = BATDRV, blue = SW)

We are looking for some help with the following questions:

1) Do you have any idea why the BQ24133 is entering into the fault mode and not exiting?

2) Why in the first design does the STAT pin blink once but then the SW restarts?  

3) Do you have another other ideas of what could be causing this?

Please see both schematics attached.Updated Design with BQ24133.pdf

Original bq24133 Design.pdf

  • 0
    TI__Genius 14430 points

    Hi Brian,

    Thanks for your question. But I couldn't see the waveform on it. Could you kindly post it again?

    About your question,

    According to this table shown below, 

    There are 4 faults will cause STAT BLINK but it will be back to normal when the fault is clear.

    We can discuss more detail on the waveform after you post it again, thank you so much!

    Best regards,

    Ann Lien

  • 0 in reply to Ann_Lien
    Prodigy 70 points

    Hi Ann,

    Thanks for taking a look a this issue.  Here are the waveforms:

    In our mass production design (that works) you can see the scope shot below that shows the BATDRV pin (blue) and the input to the 16V boost regulator (yellow) in the moment that the boost regulator is gated on through a power FET and the smart speaker starts to power on.

    In this image, you can see the BATDRV pin (yellow) and the BQ24133 SW pin (blue) in a zoomed out time scale.  When we gate on the 16V boost regulator and power up the speaker, you can see that the charger stops switching and then restarts.  We seen the BQ24133 STAT LED go off and then back on, seemingly in sync with the SW pin.  We don't know why the STAT pin is going off or why the charger starts to switch again.  However, the application works fine this way.

    In our new PCB design, that is a very similar schematic, we see the BATDRV pin engage (yellow), the SW pin (blue) stop, but then the SW pin never restarts.  The STAT LED just continues to blink until we power cycle the input.  This a show stopper in our application.  When the speaker is turned on, we need the BQ24133 to continue charging, not get stuck in a fault mode.

    Let us know if there are other scope shots that might be helpful.  

    Thanks,

    Brian

  • 0 in reply to Brian Wengreen
    TI__Genius 14430 points

    Hi Brian,

    Thanks for your waveform.

    From your schematic, what is the reason reverse Q2B drain-source direction?

    For your question and waveform,

    Only MOSFET and inductor short fault will cause charger latch-off, but the in-rush current is from VSYS.

    Did you plug-in adapter or smart speaker in below waveform? Since the SW didn't switch at the beginning. Did you plug smart speaker on the white circle timing?

    About the in-rush current, could you please add Cgs on Q2B to do the soft start to see if the latch-off issue is still there?

    Could you please take Iin, Vin, SW waveform at this condition? I want to check if there is any IDPM or input voltage abnormal behavior occurred. Thank you!

    Best regards,

    Ann Lien

  • 0 in reply to Ann_Lien
    TI__Genius 14430 points
    Hi Brian,

    Another thing need to be confirmed. You mentioned that when the loading current grows, battery will provide additional power to system. But bq24133 won't let battery and adapter power system simultaneously. When system reach input current limit, charger will decrease charging current gradually until charging current decreases to zero.

    Best regards,
    Ann Lien
  • 0 in reply to Ann_Lien
    Prodigy 70 points
    Hi Ann,

    I really appreciate your advice. We added the Cgd capacitance to Q2B as you recommended and it fixed the problem. So the issue was actually not related to the BQ24133 at all, but instead just our external circuit.

    We are very happy with the BQ24133 and we plan to use again for many future products.

    All the best,

    Brian
  • 0 in reply to Brian Wengreen
    TI__Genius 14430 points
    Hi Brian,

    Awesome!!! Thanks for your support on testing and We're happy to figure out this issue. Hope our device could be the best choice on future product.

    Best regards,
    Ann Lien