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BQ27Z746: BQ27Z746YAHR

THESNI ASHRAF
Prodigy 90 points
Part Number: BQ27Z746
Other Parts Discussed in Thread: EV2400, BQSTUDIO

Tool/software:

We are currently testing the BQ27Z746YAHR fuel gauge and BQ25628ERYKR and have observed behavior that we would like to clarify.

During our testing, we noticed the following:

  1. We connected a 3.7V, 1500mAh battery to the battery connector prior to flashing or programming the fuel gauge.
  2. In this state, we observed that the PACK pin of the BQ27Z746YAHR fuel gauge,measures approximately 0.7V assuming that the fuel gauge may not be sensing the battery correctly .

Could you please confirm if this is the expected operation for this device

If this is not the expected behavior, could you provide guidance on what we should expect to see and if there are any steps we should take to address this issue? Please refer the attached dsn for your reference

  • 0
    TI__Mastermind 24531 points

    Hello, 

    Is there a load/system connected to PACK? What is the state of the CHG and DSG FETs? 

    Regards, 

    Jonny. 

  • 0 in reply to Jonny
    Prodigy 90 points

    BAT pin of charger ic(BQ25628ERYKR) is connected to pack pin of fuel gauge ic (BQ27Z746YAHR) as depicted in the above dsn image. We would greatly appreciate your clarification on :

    1.what is the default state of CHG and DSG pins when battery is connected 

    2.Is any specific configuration needed to turn ON the FETs when a battery is connected? If so, could you please provide guidance on the necessary steps?, since during our testing When a battery is connected, the CHG and DSG pins appear to be in an OFF state.

  • 0 in reply to THESNI ASHRAF
    TI__Mastermind 24531 points

    Hello, 

    The FET state when you plug in a new battery depends on your gauge configuration, and on whether the gauge is charging or discharging. In order to ensure that the gauge is controlling the FETs automatically, you should ensure FET_EN = 1. I recommend referring to the TRM as the FET behaviors are documented there. 

    Regards, 

    Jonny. 

  • 0 in reply to Jonny
    Prodigy 90 points

    Hi

    Could you please clarify whether the FET works automatically when the battery is connected or whether we need any initial configuration to turn on the FET initially? 

    Also what are the options for enabling the charge and discharge FETs

  • 0 in reply to THESNI ASHRAF
    TI__Mastermind 37741 points

    Hello,

    Today's a national holiday. We will get back to you tomorrow.

    Regards,

    TI Apps Team

  • 0 in reply to THESNI ASHRAF
    TI__Mastermind 24531 points

    Hello, 

    I believe my last response answered this. When FET_EN = 1, then the gauge automatically controls the CHG and DSG FETs. If FET_EN = 0 then the CHG and DSG FETs should be off until you send the CHG FET Toggle or DSG FET Toggle commands. So if the FET_EN = 1, then the FETs should be automatically controlled by the gauge when a battery is inserted. 

    Regards, 

    Jonny. 

  • 0
    Prodigy 90 points

    Hi Jonny,

    We enabled FET and now both the FETs are turned ON, but when we checked the voltage across SRP and SRN while USB is connected and battery is connected at fuel gauge it shows 0v,assumes that it is in relax mode (ie, No charge/discharge is occuring); but Charging works fine when the battery is connected directly to the charger IC without the fuel gauge. Could you please help us to resolve this issue

  • 0 in reply to THESNI ASHRAF
    TI__Mastermind 37741 points

    Hello Thesni,

    Jonny is currently out of office, he should get back to you tomorrow.

    Regards,

    Nick Richards

  • 0 in reply to Adrian
    Prodigy 90 points

    Hi

    We can charge via fuel gauge by mounting a 10K thermistor at the charger IC (R277) and toggling the FET at the fuel gauge on a board with voltages of 3.7V at V_VDD_FG_R, 3.9V at pack+, and 3.7V at FB16 (output of charger IC), but when we do the same on another board with voltages of 3.1V at pack+ and FB16 (output of charger IC), and V_VDD_FG_R as 3.7V with a 3.7V,1500mAH battery,we are not able to charge. Could you please clarify on this?

  • 0 in reply to THESNI ASHRAF
    TI__Mastermind 24531 points

    Hello, 

    I am not sure what the question is here. It seems as though when you attach a battery and have FET_EN = 1 that both of the FETs are turned on? This is the expected behavior, because if both FETs were off then you would not be able to charge/discharge the battery. 

    Regards, 

    Jonny. 

  • 0 in reply to Jonny
    Prodigy 90 points

    Question here is that We can charge via fuel gauge by mounting a 10K thermistor at the charger IC (R277) and toggling the FET at the fuel gauge on a board with voltages of 3.7V at V_VDD_FG_R, 3.9V at pack+, and 3.7V at FB16 (output of charger IC), but when we do the same on another board with voltages of 3.1V at pack+ and FB16 (output of charger IC), and V_VDD_FG_R as 3.7V with a 3.7V,1500mAH battery,we are not able to charge. Could you please clarify

  • 0 in reply to THESNI ASHRAF
    TI__Mastermind 24531 points

    Hello, 

    You should be able to charge as long as the CHG FET is closed. If the CHG FET is open then you will not be able to charge the battery. 

    Regards, 

    Jonny. 

  • 0 in reply to Jonny
    Intellectual 360 points

    Dear Jonny,

    I am writing to provide an update on the current state of our board and to seek your guidance on a persistent issue we are facing.

    We are encountering difficulties with charging and discharging a 3.7V, 1500mAh LiPo battery through the fuel gauge. However, when we connect the battery directly to the BAT pin of the charger IC, bypassing the fuel gauge, the battery charges and discharges normally. Upon reviewing the register values, we have observed a UTD error in the control status register, which appears to be obstructing both charging and discharging operations via the fuel gauge.

    At present, while the fuel gauge is detectable, we are unable to configure it or write to any of its registers. Additionally, the temperature readings are inconsistent, fluctuating between values such as 0, 45, and 355 degrees, which suggests an issue with the temperature measurement.

    I have attached the register readings obtained through BQStudio using the EV2400 interface for your reference.

    Could you please provide guidance on how to address these issues?

    7536.Fuel gauge Register readings.zip

  • 0 in reply to Gopika Raj V S
    TI__Mastermind 24531 points

    Hello, 

    It looks like there is an issue with your thermistor. I think some good things to check would be to ensure that the thermistor is operational, and once confirmed, I would ensure that you have performed a temperature calibration. 

    Regards, 

    Jonny. 

  • 0 in reply to Jonny
    Intellectual 360 points

    Hello Jonny,

    I wanted to update you on the recent work we've done and seek your assistance with a couple of ongoing issues.

    We have replaced the NTC component in the board at the charger IC section and attempted to calibrate the temperature value. Despite these efforts, the UTD error continues to persist.

    Additionally, on another board, we are encountering an OTC error that is preventing us from charging or discharging via the fuel gauge.

    Could you please help us resolve these problems on both boards?

    Thank you in advance for your support.

  • 0 in reply to Gopika Raj V S
    TI__Mastermind 24531 points

    Hello, 

    Are you seeing this behavior across multiple devices? 

    Regards, 

    Jonny. 

  • 0 in reply to Jonny
    Intellectual 360 points

    Hi Jonny,

    We are currently encountering issues with two out of five boards and I would appreciate your insights on the matter. Here’s a summary of the problems encountered:

    1. Boards Showing Issues: Two of the five boards are experiencing difficulties with charging and discharging via the fuel gauge, although they function correctly with the charger IC.

    2. Specific Issues:

      • Board with OTC Error: One board is displaying an OTC error. We replaced the fuel gauge since the I2C was unresponsive, but this resulted in the OTC error appearing.
      • Board with UTD Error: The second board initially showed a UTD error. We changed the external temperature monitoring to internal temperature (TSInt) by writing 01 to the temperature enable register. This action resolved the UTD error and allowed discharging to occur. However, after refreshing, all the register values automatically reset to zero. Despite attempting to write 01 to the temperature enable register again, we lost the discharging capability and are now unable to get charging or discharging to function on this board.

    Could you please provide your thoughts on the following?

    • Potential causes for these issues.
    • Suggestions for resolving the OTC and UTD errors.
    • Any additional steps we should take to diagnose or fix these problems.

  • 0 in reply to Gopika Raj V S
    TI__Intellectual 2020 points

    Hello Gopika,

    Can you send us the gg and log files? This could be related to the protections.

    Regards,

    Siddharth

  • 0 in reply to Siddharth Venkatesan
    Intellectual 360 points

    Hi Siddharth,

    We recently replaced the fuel gauge on the board that was displaying an OTC error. After replacing it, we toggled the FET to the ON state, and the OTC error has been resolved. However, we are still experiencing issues with charging and discharging via the fuel gauge.

    I have attached the read register values from the board for your reference. Could you please review these values and provide guidance on the next steps to troubleshoot and resolve the issue?

    Fuel_guage_Values_1_8_24.xlsx

  • 0 in reply to Gopika Raj V S
    TI__Intellectual 2020 points

    Hello Gopika,

    Is this a custom formatted file? We would need the gg files exported from bqStudio.

    Regards,

    Siddharth

  • 0 in reply to Siddharth Venkatesan
    Intellectual 360 points

    Hi Siddharth,

    Yes it is.

    I wanted to inform you that we have handed over the EVK to our customer. As a result, we are currently unable to export the GG file using BQStudio.

    Instead, we are reading the shared register values using Silicon Labs' Simplicity Studio.

  • 0 in reply to Gopika Raj V S
    TI__Intellectual 2020 points

    Hello Gopika,

    No worries, thanks for letting us know.

    We are looking into this and will get back to you on Monday.

    Regards,

    Siddharth

  • 0 in reply to Siddharth Venkatesan
    Intellectual 360 points

    Hi Siddharth,

    Gentle reminder.

  • 0 in reply to Gopika Raj V S
    TI__Mastermind 24531 points

    Hello, 

    In order to get a full understanding of what is occurring, we will need to have a gg file and a log file showing this behavior. Additionally, something you can try in the meantime is to turn off the Auto Refresh (on the top left in bqStudio) when you are trying to write to the gauge. Having the Auto Refresh turned on could cause some writes to not properly execute.  

    Regards, 

    Jonny. 

  • 0 in reply to Jonny
    Intellectual 360 points

    Hi Jonny,

    Please find the attached GG file. Please note that the auto-refresh feature is already in turned off state.

    testboard1.gg.csv

  • 0 in reply to Gopika Raj V S
    TI__Mastermind 24531 points

    Hello, 

    Thank you for the configuration file, please update this thread when you have obtained the log file. 

    Regards, 

    Jonny.