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BQ40Z50: Exiting sleep mode via the !DISP pin

John Wright
Intellectual 330 points
Part Number: BQ40Z50
Other Parts Discussed in Thread: , BQ4050

We are evaluating a battery pack from a vendor that uses the BQ40Z50.

The existing configuration puts the pack in sleep mode if it is left idle for a time (a few days).

The pack exits sleep mode if a voltage is applied to +/- pins of the pack as verified by an external lab power supply.

But the concerning scenario is when the pack is charged, left long enough to enter sleep mode and then carried on an airliner and the customer/airport authorities want to check SOC.

The user would likely press the charge status indication with the pushbutton connected to the BQ40Z50 DISP pin, expecting the LEDs to indicate charge status.

But this doesn't indicate charge status as no LEDs light, making the pack appear discharged.

Putting the pack on a smart charger or applying an external voltage to +/- exits sleep and the charge status LEDs work again, but these methods might be unavailable to an airline passenger.

If pulling !DISP low would always exit sleep mode,  it would give the advantages of sleep mode while providing a local wakeup.

I do not see a way for this to be configured in the BQ40Z50.

An added advantage would be a customer who had a sleeping pack they wanted to use with a portable device that is solely powered by the pack, could wake up the pack and then plug it in.

Thanks,

John Wright

  • 0
    TI__Mastermind 24870 points

    Is this the bq40z50 or the bq40z50-R1?

  • 0 in reply to Kang Kang
    Intellectual 330 points
    the BQ40Z50.

    The supplier may be willing to go to the -r1 version if that provides some advantages.

    John Wright
  • 0 in reply to John Wright
    Expert 2475 points
    John
    Are you referring to Sleep mode or Shutdown mode? I would think that the LEDs could still work when in Sleep mode, because the gauge returns to normal mode when it reads the voltage and current. You may have to hold the DISP button down for several seconds as the polling sequence time has been increased. Applying voltage to P+ is not required to exit Sleep mode, where is it required to exit Shutdown mode. The device is completely disabled when in Shutdown and no features are available. Applying voltage to P+ is the only option to wake the gauge from Shutdown.
  • 0 in reply to TEC
    Intellectual 330 points

    I believe it is in sleep mode as it is nearly fully charged.

    Sleep mode is in the "DA Configuration"  address 0x4950, but as the pack is sealed, I can't read this information with the EV2300.

    My assumption that it is in sleep mode could be invalid.

    Per the bq40Z50 technical reference(SLUUA43A.pdf), sleep is exited under these conditions

    1. current > configuration sleep current

    2. wake comparator trips

    3. SafetyAlert() flag or PFAlert() flag is set

    4. SMBus connected

    5.... thers

    But I can find no indication that pressing in the Technical reference that pressing  the !DISP button will take the BQ4050 out of sleep.

    I also directed my question to the manufacturer of this prototype battery, but have not heard back.

  • 0 in reply to John Wright
    Expert 2475 points
    The DISP pin is not a Sleep wake-up criteria. You can check to see which mode the gauge is in if you have access to the thermistor. You should see it pulse every 250ms when in normal mode, every 5 to 20 seconds when in Sleep mode and no pulses at all when in Shutdown mode.
  • 0 in reply to TEC
    Intellectual 330 points
    I don't have access to the thermistor without cutting into the pack as it is both sealed from access via the EV2300 tool and physically sealed in the plastic case.

    I asked the vendor for information but they have not responded yet.

    Again, thanks for all the advice.