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BQ40Z50: Turning on / off LED trigger

Cameron Perl
Expert 5305 points
Part Number: BQ40Z50

Hey team,

One of my customers had a slight design change request from their end customer and are looking for a way to disable the LEDs during a somewhat unique event. To give some more detail there are two use cases:

  1. Normal operation using a type-C cable. Chg/Dsg occurs normally and the user can see the SoC when a PB event occurs
  2. When the product is inserted into an device using the contacts on the top of the housing bypassing the type-C but using PD protocol. Whenever the product is inserted into a device, it will be discharging and powering that device – charging will never occur. When the product is seated in the device and a double tap/PB event occurs (more or less an on switch), the LEDs will light up and there will be light leakage. This is the issue. When the product is in the device, the PB event can still occur and illuminate the LEDs.

Their main ask is if there's a condition or setting that cane be changed within the BMS to disable the LEDs while it is connected to said device. The customer identified that it appears you can send the SMBus cmd to disable the PB but then there is no way to enable it once the product is disconnected from the device. 

Thanks and let me know if you need more info!

  • 0
    TI__Guru** 105590 points

    Hello Cameron,

    Can you share their .gg file so we can look at their LED config?

    What are the exact conditions for the pack that it would need to not enable the LEDs?

    Sincerely,

    Wyatt Keller

  • 0 in reply to Wyatt Keller
    TI__Expert 5305 points

    Hey Wyatt,

    Thanks for your patience here's the GG file. For exact conditions are you referring to voltage levels?

    One brief additional question: when you disconnect the device, does that count as a reset and hold the LEDs high for 2x LED Hold Time? Or is this time held governed by something else. (they current are on for 60s, end user wants 15s; first samples were delivered recently for feedback)

    STUB_03_09.gg.csv

  • 0 in reply to Cameron Perl
    TI__Guru** 105590 points

    Hello Cameron,

    I see the only setting in the LED config is LEDCHG (0x04) and the LED_EN bit is set for the DISP pin activation.

    For the button press I don't think there's a good way to disable it via settings unless manually controlled by the MCU, when the button is pressed it will turn the LEDs on with the config currently.

    The time you're seeing is the switching between modes (chg relax time) the gauge will stay in charge mode even after current has dropped off.

    It should be okay to reduce the time as long as they don't hover around any of the transition current zones long.

    Sincerely,

    Wyatt Keller

  • 0 in reply to Wyatt Keller
    TI__Expert 5305 points

    Hey Wyatt,

    Yeah we were thinking that it was unlikely to be able to account for this in the BQ's firmware, but wanted to double check. 

    I'll let them know about the Chg Relax Time - couldn't figure out exactly what it was in the datasheet!

    Appreciate the help as always.

    Cheers,

    Cameron