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BQ40Z80: About the use of EMSHUT function of BQ40Z80

zhang jianhang
Prodigy 130 points
Part Number: BQ40Z80


Hi TI experts，

I used the 17Pin of BQ40Z80 as the function button of EMSHUT. For example, when I press the button, the battery turns off the output, and when I press the button again, the battery turns on the output, which is used as the battery on and off key repeatedly. At the same time, the EMSHUT-EXIT-VPACK register is turned on. After pressing the button to turn off the battery output, charging can reactivate the battery and turn on the charge and discharge MOS.


However, in the process of charging and discharging (charging current > discharging current), the customer found that if the button is pressed by mistake, the battery will briefly turn off the output (about 750ms). The electrical appliances are suspended, the experience is not good. So can the button action of the EMSHUT function be shielded during the charging process?It is required that the output of the battery is not turned off during charging.


Looking forward for your reply, thank u.

BQ40Z80-EMSHUT.gg.csv

  • +1
    TI__Genius 11770 points

    Hello Zhang,

    So if I understand correctly, you would like to disable the EMSHUT function during charging/discharging? One way could be to use the CHG/DSG bits; you could have the host scan for the CHG/DSG bits being high, and responding by setting EMSHUT = 0, and vice-versa. I'm not sure if there is an easier solution, given the EMSHUT button has very high priority as a HW detection. You may also be able to accomplish a similar result via HW (referencing the button to the CHG FET gate somehow which accomplishes what you desire). However, I would likely need a schematic and am not aware of any existing implementations, so there would be some risk as well as redesign. 

    Let me know if you have any thoughts on either of these ideas or any other ideas you would like check.

    thanks,

    Alex M.

  • 0 in reply to Alexander Mazany
    Prodigy 130 points

    Hi Alex,
    Thank you for your answer.
    Yes, I want to turn off the EMSHUT function during the charging process. Now it seems that setting EMSHUT=0 and the host scan to judge the charging and discharging status is the best solution.

  • 0 in reply to zhang jianhang
    Prodigy 130 points

    Sorry, my network is stuck.