• State Resolved
  • Locked Locked
  • Replies 9 replies
  • Answers 1 answer
  • Subscribers 63 subscribers
  • Views 987 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

BQ24296: Not switching to Fast Charging mode

FabrizioP
Intellectual 380 points
Part Number: BQ24296
Dear Sir/Madam,
 
I have been debugging our battery charging schematic that uses the BQ24296 IC, however I have not been able to get the system to reach ‘Fast Charge’ mode.
No matter what settings I change, the system always remains in pre-charge mode, with no fault, and REG08[0] is 1 when read (VSYSMIN regulation).
 
Please see the schematic and snapshot of the register values (below) taken during debugging (bq2429x_g_reg[0:10] in the image follows the same order as REG[00:0A]).
 
More info:
- Measurements on the PCB show that the USB_VBUS voltage is 5V, and the V_SYS voltage is 3.97V.
- The board is connected to a power adapter throught a USB C - USB 2 cable.
- The power adapter can provide up to 2.1A.
- CEn pin is low  during the charging phase
- OTG pin is low  during the charging phase
- PSEL pin is low  during the charging phase
 
Please could you help with the following:
- What is the meaning of REG08[0] (VSYS_STAT)? It says that this bit is 1 when BAT < VSYSmin, however our VBAT is 3.97V and our VSYSmin is 3V (REG01[3:1]), and yet this bit is 1.
- What is supposed to be the value of EN_HIZ bit (REG00[7])? I have found out that if it is set to 1 the chip charges (even if it does not switch to Fast Mode), otherwise it does not.
I would appreciate if you could please help with this issue,
Best regards
Fabrizio
  • 0
    TI__Guru 57651 points

    Fabrizio,

    What are VBUS, VSYS, VBAT voltages measured at the corresponding pins of BQ24296? And what is the actual charging current?

    Thanks,

    Ning.

  • 0 in reply to Ning T
    Intellectual 380 points

    Hi Ning,

    Thanks for getting back promptly. Below are the values you requested:

    Vbatt = 3.987V

    Vsys = 3.989V

    Vbus = 5.171V

    Fast Charging current (set by R21) = 2.7A

    Pre-Charge current (set in I2C) = 256mA.

    Regards,

    Fabrizio

  • 0 in reply to FabrizioP
    TI__Guru 57651 points

    Fabrizio,

    REG08[0]=1 indicates the device is In VSYSMIN regulation (BAT <VSYSMIN), but your measurement shows VSYS is greater than VSYSMIN. Are you measuring VSYS, VBAT at the pins of the BQ24296 instead of test points on your board?

     

    And what is the actual charging current to your battery?

    Thanks,

    Ning.

     

  • 0 in reply to Ning T
    Intellectual 380 points

    Dear Ning,

    Yes, I have mesured all values at the pins of the BQ24296, their values are as stated:

    Vbatt = 3.987V

    Vsys = 3.989V

    Vbus = 5.171V

    But still, it does not charge in fast mode.

    Any suggestions?

    Please could you help with the following questions too:
    - What is the meaning of REG08[0] (VSYS_STAT)? It says that this bit is 1 when BAT < VSYSmin, however our VBAT is 3.97V and our VSYSmin is 3V (REG01[3:1]), and yet this bit is 1.
    - What is supposed to be the value of EN_HIZ bit (REG00[7])? I have found out that if it is set to 1 the chip charges (even if it does not switch to Fast Mode), otherwise it does not.

    Best regards

    Fabrizio

  • 0 in reply to FabrizioP
    TI__Guru 57651 points

    Fabrizio,

    REG08[0] is 1 indicates the device is In VSYSMIN regulation (BAT <VSYSMIN), but your measurements show VSYS is greater than VSYSMIN. Are you measuring VSYS, VBAT at the pins of the BQ24296 instead of test points on your board?

     

    And what is the actual charging current to your battery?

    Thanks,

    Ning.

     

  • 0 in reply to Ning T
    Intellectual 380 points

    Ning,

    I can confirm that my measurements have been taken directly at the pins of the BQ24296.

    What is supposed to be the value of EN_HIZ bit (REG00[7])?

    My assumption was that it must be set to 1, is it correct?

    Battery specs are the following:

    - Li-ion battery pack

    - Nominal Voltage: 3.63V (although current value is 3.98V)

    - Nominal Capacity: 7.0Ah

    - Nominal Energy: 25.41Wh

    - Max Charge Current: 3.4A

    - Charge Voltage: 4.3V

    I look forward to reading some good advice from you.

    Best regards

    Fabrizio

  • 0 in reply to Ning T
    Intellectual 380 points

    Ning,

    Do you have any update?

  • 0 in reply to FabrizioP
    TI__Guru 57651 points

    Fabrizio,

    EN_HIZ bit (REG00[7]) should be "0" for normal operations. The default value is "0".

    Could you please try another fresh BQ24296 device on the board and try again?

    Thanks,

    Ning.

  • 0 in reply to Ning T
    Intellectual 380 points

    Thanks for your help.

    It came out that D10 (protection diode) was causing an issue (it reduces drastically voltage of TS).

    If you follow the schematic provided with this thread, do not populate that diode and keep HIZ low.