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BQ40Z50: System_Present

Yuta Nishie
Genius 5015 points
Part Number: BQ40Z50
Other Parts Discussed in Thread: BQ24620, , BQ25820, BQ24773

Tool/software:

Hi,

Although it is a different part number, when I combined a TI charge IC on the charger side with a gas gauge IC from another company on the battery pack side, the charge IC's BAT_Present signal could not be processed and charging was not possible even when the charger and battery pack were connected. When the battery pack side is in sleep mode, both the charge/discharge FETs are OFF, the BAT_Present signal cannot be processed and charging does not occur.

I referred to the BQ24620 datasheet "8.3.21 Battery Detection" and the BQ40Z50 datasheet 9.2.2.2.3~9.2.2.2.4.

1. Is it possible to avoid the above condition when combining BQ24620 and BQ40Z50?

2. Also, have there been any cases where the above condition has occurred with these combinations?

3. Can the BQ40Z50 detect the System_Present detection signal even in sleep mode?

Best Regards,

Nishie

  • 0
    TI__Mastermind 27321 points

    Hello,

    Configure     the BQ40Z50 to keep the CHG FET on in sleep mode or optimize the wake function to respond to the BQ24620’s detection pulses. External wake circuits can be added if needed.

    Similar issues have been discussed on TI E2E forums, particularly with the BQ40Z50’s FETs off in sleep mode preventing charger detection. No exact match for BQ24620 + BQ40Z50, but the pattern suggests configuration adjustments can resolve it.

    The BQ40Z50 can detect the PRES signal in sleep mode, enabling wake-up when a system is connected, provided the PRES pin and wake function are correctly configured.

  • 0 in reply to Jose Couso
    Genius 5015 points

    Hi Jose-san,

    Thank you for your kind response.

    Could you please suggest a solution that can solve "the BQ40Z50's FETs off in sleep mode preventing charger detection"?

    Also, could I tell you the specifications of the battery and charger, and you could suggest me a solution that can solve the problem?

    If possible, I would like to communicate via private message to tell you the specifications.

    Best Regards,

    Nishie

  • 0 in reply to Yuta Nishie
    TI__Mastermind 27321 points

    Hello,

    My recommendations for BQ40z50 are:

    1- Enable the setting that keeps the charging switch (CHG FET) on during sleep mode. This allows the charger to see the battery’s voltage and start charging.
    Check FET Options register for this

    2- Modify the Sleep Current and Sleep Voltage settings to delay sleep mode entry, reducing the likelihood of the BQ40Z50 being in sleep mode when the charger is connected.

  • 0 in reply to Jose Couso
    Genius 5015 points

    Hi Jose-san,

    Thank you for letting me know about the countermeasure. Am I correct in understanding that by implementing this countermeasure, BQ40Z50 and BQ24620 will be integrity?

    I have also sent you a private message. I would appreciate it if you could check it.

    Best Regards,

    Nishie

  • +1 in reply to Yuta Nishie
    TI__Mastermind 27321 points

    Hello,

    Yes, you’re correct that implementing these countermeasures should ensure the BQ40Z50 and BQ24620 work together reliably, resolving the charger detection issue caused by FETs being off in sleep mode. The primary solution (keeping CHG FET on) is straightforward and effective.
  • 0 in reply to Jose Couso
    Genius 5015 points

    Hi Jose-san,

    Thank you for letting me know the solution.

    I have an additional question.

    Do you have any information on whether the same issue occurs with the combination of BQ40Z50 and BQ25820, or BQ40Z50 and BQ24773? In these cases, will keeping the CHG FET on solve the problem?

    Best Regards,

    Nishie

  • 0 in reply to Yuta Nishie
    TI__Mastermind 27405 points

    Hello Yuta,

    Jose is currently out of the office and will be return early next week.

    Thank you,
    Alan

  • 0 in reply to Yuta Nishie
    TI__Mastermind 27321 points

    Hello,

    I do not think it is a charger-gauge combination issue, but rather ensuring the gauge's FETs are ON when charger current is applied.  

  • 0 in reply to Jose Couso
    Genius 5015 points

    Hi Jose-san,

    1. Is my understanding correct that the way to check that the FET is on is to read the corresponding register with I2C? If so, which register should I read?

    2. Also, could you tell me how to turn the FET of the gauge on? I found the register "FORCE _BATFET_ OFF," but I did not know the register to turn it on.

    Best Regards,

    Nishie

  • +1 in reply to Yuta Nishie
    TI__Mastermind 27321 points

    Hello,

    To read from BQ40z50 register for CHG FET, please use OperationStatus() register.

    CHG/DSG bits indicate FETs are ON.
    XCHG/XDSG bits indicate FETs are off. 



    The snippet you attached looks for the charger device. Please use gauge TRM for this info.

    The gauge's firmware controls the FETs if FET_EN is ON.
    When FET_EN is OFF, the user can send the CHG FET TOGGLE command to toggle the FET. Note that this is only recommended for testing purposes (FET_EN = 0)