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BQ4050: Method to wakeup a companion MCU

Part Number: BQ4050
Other Parts Discussed in Thread: BQ40Z50

Hi,

We are working on a battery product which will have the BQ4050 as its BMS.

The product shall also have a companion MCU which is to monitor the battery whenever it is in charge or discharge state.

I understand that I can use the LED signals to wake up the MCU when it is in charge state.

However I can find no information on how I can wake up the MCU when the battery is being discharged without repeatedly polling the BMS through communications.

Therefore is there a method/signal which can be used to wakeup the MCU from a sleep signal if the BMS is discharging current?

Similarly does the BQ4050 have a signal to indicate that the BQ4050 is in shutdown mode? Can the BTP_INT signal be used for this purpose?

Thanks and regards,

Andre Cilia

  • Hello Andre,

    I assume you are using the LEDCHG feature to act similar to an interrupt for charging. There is no corresponding feature for the BQ4050, you would need to one of the most recent BQ40Z50 firmware releases in order to have GPIO configurability where you can set an interrupt based on a register bit.

    Once the gauge is in shutdown everything will be off, there is no way for the gauge to send an interrupt.

    Sincerely,

    Wyatt Keller

  • Hi Wyatt,

    Thanks for your reply.

    With regards to the shudown, GPIO pins would be low? If yes, can a GPIO pin be set to default high whenever the gauge is not in shutdown mode?

    Thanks and regards,

    Andre Cilia

  • Hello Andre,

    GPIO pins will be high impedance in shutdown. You will be able to see pulses on PRES for removable pack, not sure if this is something you could use since it's a pulse.

    Sincerely,

    Wyatt Keller

  • Having the GPIOs in high impedance mode shouldn't be an issue since a pulldown resistor should be able to pull it low when in shutdown mode.

    I have not yet understood exactly the function of the PRES pin however. Is this used for battery packs where the cells are removed entirely from the BMS?

  • Hello Andre,

    Yes you could do that, it would require external logic.

    Yes, the PRES pin is used to determine if the battery pack is inserted into the system. It pulses every 250ms for a short duration.

    Sincerely,

    Wyatt Keller