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BQ25798: CHG_STAT value in case of fault condition and other questions

Romaric MAILLARD
Prodigy 10 points
Part Number: BQ25798

Tool/software:

Hello TI community,

I have a few questions regarding the BQ25798 device. We are using this IC to charge a 2S custom-built battery pack for one of our new products.

Question 1:

p. 33 the of the BQ25798 datasheet (doc SLUSDV2B revised Jan. 2023) says :

“The host can monitor the ADC BAT pin voltage and TS fault register to determine when a valid battery is attached.”

We might have missed it but §9.5.1 (Resgister map) doesn’t mention such a register (REG20 and REG21 fault registers do not seem to have a “TS fault” field either). Could you please provide us with more details about this “TS fault” register ?

Question 2:

Assuming the BQ IC is charging the battery (i.e. CHG_STAT of REG1C is either 1h, 2h, 3h or 4h), what is the value of CHG_STAT (REG1C) when one of the charging timers (trickle, pre-charge, fast charge) expires? Does CHG_STAT roll back to 0h (not charging) ?

Question 3:

Assuming the BQ IC is charging the battery, when a VBUS over-voltage (VBUS_OVP), VBAT over-voltage or IBUS over-current (IBUS_OCP) condition occurs, which value does CHG_STAT (REG1C) take ?

Question  4:

When a VSYS over-voltage condition occurs, is VSYS supplied from the battery ? If the battery was charging, which is the new value of CHG_STAT once VSYS_OVP_STAT is set (indicating the over-voltage situation) ?

Question 5:

Assuming the battery is charging, what is the value of CHG_STAT when TS temperature goes higher than T5 (TS_HOT condition) or lower than T1 (TS_COLD condition) ? Can you please confirm that charging is suspended in those cases ?

Question 6:

When a TSHUT_STAT condition occurs, can you please confirm that battery charging is suspended ? In such a case, what is the value at VSYS ? If battery charging was ongoing, what is the value of CHG_STAT once TSHUT_STAT is set ?

Many thanks in advance for you support

Kind regards

Romaric

  • 0
    TI__Guru**** 165986 points

    Hi Romaric,

    Regarding 1, the TS fault register (s) refers to the TS hot, cold, warm and cool status and fault flags in REG0x1F and REG0x25 respectively.

    Regarding 2, when the pre-charge and fast charge timer expires, the charge status returns to the not charging.  When trickle charge timer expires, trickle charge auto restarts.

    Regarding 3, during VBUS_OVP, VBAT_OVP, IBUS_OCP, charge status is not charging.

    Regarding 4, during a VSYS_OVP, the converter turns off and VSYS is supplied solely by the battery.  Charge status is not charging.

    Regarding 5, charge is suspended and charge status reports not charging for TS hot and cold faults.

    Regarding 6, charge is suspended for TSHUT fault and charge status is not charging.

    Regards,

    Jeff

  • 0 in reply to Jeff F
    Prodigy 10 points

    Hello Jeff,

    Thank you so much for these answers.

    Regarding question 6, can you please tell us how VSYS is supplied when a TSHUT fault occurs : from battery? other (complete shutdown, ... ?

    Kind regards

    Romaric

  • 0 in reply to Romaric MAILLARD
    TI__Guru**** 165986 points

    Hi Romaric,

    Yes, SYS is provided by BAT during TSHUT.  

    Regards,

    Jeff

  • 0 in reply to Jeff F
    Prodigy 10 points

    Hello Jeff,

    Thanks for this answer. It is all clear now !

    Kind regards

    Romaric