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BQ25898: BQ25898

Harikrishnan Srinivasa pillai
Prodigy 70 points
Part Number: BQ25898
Other Parts Discussed in Thread: EV2400, BQ24298, BQSTUDIO

Hi,

I am trying to validate the charger Bq25898 used in one of our design.

This device is connected to BMS tool through I2C interface of 1.8V logic. After the connection checked the Device ACK is OKAY from BMS tool. The EV2400 emulator was connected.

During the device selection I have chosen "bq25898.bqz" file. But in the window it shows as "bq24298 Default view" Not sure whether its still okay.

When I read the register values its reading only the default values, not seeing any appropriate load current values.

I have the following questions.,

1. Does EV2400 supports "Bq25898" device ?

2. When load the charger configuration for "bq25898" why it shoes as"bq24298 default view" although on top it still shows as "Bq25898.bqz"

3. Why the register read values are not appropriate or not updating according to my input charger current or output load current increases?

4. I am looking for the following registers, can you please let me know the exact register number to read them?

a: Input charge current register

b. Output discharge current register.

c. Charge current regulation.

Thanks,

Harikrishnan

  • 0
    TI__Guru**** 170496 points

    Hi Harikrishnan,

    The EV2400 I2C output lines are internally pulled up to 3.3V   I have never tested with two different voltage level pull ups on the I2C lines.

    Regarding 1 and 2, the BQ24298 tab headers are a typo.  The BQ25898.bqz supports the device.

    Regarding 3, if you select Field View (far right) and then click Read Register and not have Device ACK Error as below, the registers should update.  

    Regarding 4, input current register is REG00, charge current register is REG04, control of output discharge current is not an IC feature.  There is an over discharge current clamp that has a fixed value. If you use Field View, you do not need to know the register numbers.

    Regards,

    Jeff

  • 0 in reply to Jeff F
    Prodigy 70 points

    Hi Jeff,

    I had gone through the schematics of EV2400 emulator. As per the design, it supports all the I2C logic level. Because the design can be I2C specification compatible like 1.8V/2.5V/3.3V. Since I2C is open-drain based specification, so the designer has a choice of connecting the pull-up with any of these logic levels.

    I had checked the reference design of EV2400 as well and its logic is defined based the logic level read from the SDA and SCL lines from the DUT. You may be double confirm from your end.

    My DUT interface is currently connected to 1.8V. So in my understanding that should not be a problem.

    I have also able see "DEVICE ACK OKAY" when i connect the EV2400 with my DUT.

    My concern is why the register values are not getting updated when I read from the register?

    Thanks,

    Harikrishnan

  • 0 in reply to Harikrishnan Srinivasa pillai
    Prodigy 70 points

    Hi Jeff,

    In addition, I have also probed the SDA and SCL signal after connecting the EV2400 and found that signal quality is fine and it stays at 1.8V logic level. There is no logic conflict.

    The device address is also fine for this device.

    Please let me know your thoughts.

    Thanks,

    Harikrishnan

  • 0 in reply to Harikrishnan Srinivasa pillai
    TI__Guru**** 170496 points

    Harikrishnan,

    did you disable the watchdog timer?  If not, the registers reset to defaults after the timer expires.

    Jeff

  • 0 in reply to Jeff F
    Prodigy 70 points

    Hi Jeff,

    Can you please let me know more on this watchdog timer?

    Do you mean there is some option from BMS tool to disable the watchdog timer of bq25898?

    I am not sure if there is a watchdog timer exist on this device.

    Please elaborate.

    Thanks,

    Harikrishnan

  • 0 in reply to Jeff F
    TI__Guru**** 170496 points

    Harikrishnan,

    All of our chargers have a watchdog timer bit (REG03b6) that the host must write to before it expires.  If not the registers reset to default as a safety feature.

    You can change the timer expiration time or disable using REG07b4:5.

    Regards,

    Jeff

  • 0 in reply to Jeff F
    Prodigy 70 points

    Hi Jeff,

    Thank you for the register details. I need to check on this from my Firmware team on the watchdog register value.

    On the quick check even if the watchdog timer was not disabled it should reflect the current value for 40 Sec (default timer). Which is huge time for human to see the values getting changed and reset to default value after 40 sec.

    But in my case the values are not getting updated at all. It stays some default value irrespective of the input current change or the Load current change.

    I am not able to attach the screen shot of register read values at this place.

    Thanks,

    Harikrishnan

  • 0 in reply to Harikrishnan Srinivasa pillai
    TI__Guru**** 170496 points

    Harikrishnan,

    Any updates on this?  When you write to the charger to, for example, change the charge current or disable charge, does it happen but the registers aren't reading back?  I have never seen the BQSTUDIO software report Device ACK OK but not have a successful read/write.

    Regards,

    Jeff

  • 0 in reply to Jeff F
    TI__Guru 59461 points

    Hi,

    We haven’t heard back from you for a while, the thread is considered solved and closed.

    Thanks,

    Ning.