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Original question:

BQ27546-G1: Standalone working and Other queries

BQ24158: Standalone working and Other queries

Baghiya Lakshmi
Intellectual 645 points
Part Number: BQ24158

Hi,

We are planning to use BQ24158YFFR in our design as the Battery charger. As per my understanding from the docs, we can either operate the Battery charger in 15mins mode or 32 secs mode. 
But in both modes, the system MCU has to take action before the timer times out.

Especially, in the 32sec mode, the timer reset has to be done every 32 seconds else the Battery charger would enter into High impedance mode. Is it possible to operate the Battery charger without much intervention from the MCU?

Also, Connecting the load before and after the current sense resistor - Whether it would impact the fuel gauge calibration?

  • 0
    TI__Guru**** 151946 points

    Hello,

    Unfortunately, this IC requires I2C communication in order to continue functioning at the watchdog timer expires.  Connecting a system load before the current sense resistor and the battery after the sense resistor results in the converter sending the maximum input power (as limited by input current limit and/or input voltage limit) to system. Any power remaining goes to charge the battery, with the sense resistor correctly measuring that charge current.  Connecting a system load after the current sense resistor in parallel results in the charger not being able to distinguish between charge current and system load current, especially for termination.

    I am not an expert on fuel gauges.  Most BQ24158 connect the battery in parallel with the system load.

    Regards,

    Jeff 

  • 0 in reply to Jeff F
    Intellectual 645 points

    Hi Jeff,

    Thanks for the reply.

    Also, once the Battery charger registers are configured via I2C - the Battery charger would definitely enter into a 32 second. Am I right?

    So if we are planning to use the Battery charge in OTG mode also, this 32 seconds reset is required?

    Thanks,

    Baghiya

  • +1 in reply to Baghiya Lakshmi
    TI__Guru**** 151946 points

    Hi Baghiya,

    Yes and yes.

    Regards,

    Jeff

  • 0 in reply to Jeff F
    Intellectual 645 points

    Hi Jeff,

    In the datasheet, it is mentioned that the Battery charger configuration remains the same as long as it is powered - Whether the charger configuration remains there until the Battery voltage is available or only until VBUS is available?

    Either in OTG mode or Charging mode, if the 32 seconds reset is not done. The Battery charger would enter into High impedance mode. Once, the I2C communication happens again, the Battery charger exits from the High impedance mode and enters into the previous mode and the Battery charger register configuration remains intact.

    Please confirm whether the above understanding is correct.

    Thanks,

    Baghiya

  • 0 in reply to Baghiya Lakshmi
    TI__Guru**** 151946 points

    Hi Baghiya,

    While in charge mode, if the 32-second timer expires, the charge is terminated and charge parameters are reset to default values. Then the 15-minute timer starts and the charge resumes in 15-minute mode.  To be in OTG, you have to be in and stay in 32 second mode by having the host write to the watchdog timer bit.

    Regards,

    Jeff

  • 0 in reply to Jeff F
    Intellectual 645 points

    Hi Jeff,

    So whenever the watchdog timer is not reset, then the battery charger will reset the parameters to the default values and enter into high impedance mode.

    Once again when the I2C transition happens, the battery charger will exit from the high impedance mode and enter into 15 mins mode. Once the registers are reconfigured, the battery charger will enter into 32 seconds mode.

    Thanks,

    Baghiya

  • 0 in reply to Baghiya Lakshmi
    Intellectual 645 points

    Hi Jeff,

    In the datasheet, the dc analysis values for the 1.8V pull up is given. What is the value for 3.3V pull ups?

    Thanks,

    Baghiya

  • 0 in reply to Baghiya Lakshmi
    TI__Guru**** 151946 points

    Hi Baghiya,

    The timers work as explained below, starting in 15 min mode then moving to 32sec mode and back again if no I2C write.  The BQ24158 does not go into HiZ mode after 15 min timer expires.

    The I2C thresholds are the same for 3.3V pull up.

    Regards,

    Jeff

  • 0 in reply to Jeff F
    Intellectual 645 points

    Hi Jeff,

    In the flow chart, it is mentioned like, there is timer fault after the 15mins timer expired. What happens after the timer fault?

    Thanks,

    Baghiya

  • 0 in reply to Baghiya Lakshmi
    TI__Guru**** 151946 points

    Hi Baghiya,

    For BQ24158, from datasheet section 9.3.3:

    If the 32-second timer expires, the charge is terminated and charge parameters are reset to default values. Then the 15-minute timer starts and the charge resumes in 15-minute mode.  

    The fault is reported in REG0x00 bitse3:0.

    Regards,

    Jeff