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BQ78350-R1: BQ78350-R1 current LED output

Brian Zoro
Expert 3890 points
Part Number: BQ78350-R1

Hi to everyone,

I have a question regarding the BQ78350-R1. If configured all LED outputs they are limited to 3mA output current, expect the LED5 output that provides 20mA. 
Could this be an issue in the firmware, or is this behavior a hardware issue?
Thanks in advance!

Best regards,

Brian

  • 0
    TI__Guru* 81034 points
    Hi Brian,

    3mA is what should be observed for all pins. Are you seeing the same voltage on all 5 pins when not loading with a current? Do you have a 2nd device you can try to see if the same thing is observed?

    Thanks,
    Matt
  • 0 in reply to Matt Sunna
    TI__Expert 3890 points
    Hi Matt,

    yes they tried it on different devices. What I forgot to mention is that they use the output LED5 as GPIO with 3mA configuration.
    Meanwhile they have a "solution" for this problem. They have to configure the LED5 output as a LED and then turn it on and off. After that they can use it as GPIO and also the 3mA limit is active.

    Firmware error in the BQ78350-R1?

    Best Regards,
    Brian
  • 0 in reply to Brian Zoro
    TI__Guru* 81034 points
    Hi Brian,

    It's good to hear they have a work-around and thanks for letting us know about this observed behavior. I will need to investigate this to find whether this is caused by the hardware or the firmware. This will take a few days before I am able to dig into this, but I will let you know what I learn.

    Best regards,
    Matt
  • 0 in reply to Matt Sunna
    TI__Guru* 81034 points
    Hi Brian,

    I am not able to test this easily on an EVM since there are no test points for these pins and LEDs are connected. I did look into the firmware and cannot find anything that could explain this behavior.

    Can you let me know the exact sequence used to configure these pins? There are some steps outlined in the "Using the BQ78350-R1" app note (section 4.1). I'm not sure if it is anything they are not already doing: www.ti.com/.../slua924.pdf
    Some of the settings settings need to be set upon reset while others can be updated after the device is running.

    Best regards,
    Matt
  • 0 in reply to Matt Sunna
    TI__Expert 3890 points

    Hi Matt,

    Sorry for the late answer. So they looked through the initialization again and found nothing conspicuous. The sequence that they use to configure:

    •     GPIO configuration(0x449B) register to 0x20
    •     GPIO Output Enable(0x449C) register to 0x3E
    •     GPIO Default Output Enable(0x449D) register to 0x3E
    •     GPIO Type(0x449E) register to 0xC0
    However, there has been another problem:
    They activate the LED indicator while charging.
 If they now charge the battery pack and then unplug it, the LEDs continue to light until the value AverageCurrent () falls below the set QuitCurrent (up to 25s).
 Is that supposed to be so, or should it not be derived from the mean current (not average)?

    Thanks and best Regards,
    Brian
  • 0 in reply to Brian Zoro
    TI__Guru* 81034 points
    Hi Brian,

    CHARGE mode is exited and RELAX mode is entered when Current() goes below Quit Current for a period of Chg Relax Time. The default value of Chg Relax Time is 60s, but this can be modified. Do you think this is the delay they might be observing?

    Matt
  • 0 in reply to Matt Sunna
    TI__Expert 3890 points
    Hi Matt,
    Thanks! yes It´s the delay!
    do you maybe have some news regarding this GPIO Problem?

    Best regards,
    Brian
  • 0 in reply to Brian Zoro
    TI__Guru* 81034 points
    Glad to hear the delay fixed the issue.

    I haven't been able to find anything that explains the GPIO issue they are seeing. Do you know if they are doing a Reset after applying the settings to the GPIO data flash? Do they still need to toggle it off and on in this case?

    Thanks,
    Matt