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BQ27426: Questions on TRM of SLUUBBO Document

Andy Sarangi
Intellectual 270 points
Part Number: BQ27426
Other Parts Discussed in Thread: BQ27427, TIDA-01012, EV2400

Hi,

I've couple of questions for the fuel gauge: BQ27426

We are using BQ27426 and info from the application example (page 18, document date: SLUUBBO-December 2015) is not quite clear. In the document, page 35 (data flash summary table) Offset for  design capacity is 6, design energy is 8 , termination voltage is 10 and taper-rate is 21; all numbers are in decimal. However I'm not clear how the application example (page-18) concludes the offset is 0x4A for design capacity instead of 0x46? Which one is correct - 0x4A or 0x46?

On our board, we don't use BIE auto detect; We have gauge's BIN pin and charger's TS pin shorted to Vss with a 10K pulldown. In order to store the design capacity info and successfully use the fuel gauge should we clear the BIE setting to 0 in bit-5 (OpConfig - Register) from the default setting of "1" before we store design capacity and other info? Should we use BAT_INSERT command before we start storing new design capacity info? If not then at what sequence we need to issue BAT_INSERT command? Do we need to update the checksum of OpConfig register  if we clear the BIE bit? 

In order to change Chem-ID to 1202 do we need to write 0x01 or 0x00 to the Chem-ID register 0x0031?  

Instead of writing various data to the gauge programmatically in steps is it possible to update gauge's flash memory in one go with all the changes? Where can I find info on how to update flash memory altogether?

Thank you for helping,

- Andy

  • 0
    TI__Mastermind 19195 points

    Hi Andy,

    There is as typo, please go by table 7-2 and use 0x46 as the offset. 

    0x0031 is the CNTL data for control command, see TRM 5.1.

    If you are not using the hardware protection then you will need to send the BAT_INSERT command when the battery is inserted.

    BQ27427 is a rom gauge and contains no flash.

    Best regards,

  • 0 in reply to Nick Brylski
    Intellectual 270 points

    Thank you Nick for helping.

    I was going through the tidcdb7 (TIDA-01012 Application v2.0 with BLE access to BQ27426 gauge characteristics) project info done by TI.

    I found some definitions that are confusing and not referred at all BQ27426 SLUUBB0 / TRM.

    For example:

    #define Chem_Data_SubClass_ID    0x6D00

    #define OCVa_0_SubClass_ID     0x5300
    #define OCVa_1_SubClass_ID     0x5301
    #define OCVb_0_SubClass_ID     0x5400
    #define OCVb_1_SubClass_ID     0x5401
    #define Resistance_Low_Temp_SubClass_ID      0x5500
    #define Resistance_High_Temp_SubClass_ID     0x6C00

     Can you please tell me  where these definitions / subclass IDs are in BQ27426 TRM for OCV, Chem_data_subclass and Resistance_low/high_temp?  I can't find it at all

    tidcdb7 project application code says  Ra_Tables_SubClass_ID has 32 data  as below but TRM says it has 14 entries (section 7.4.3.1)

    Ra_Tables[32] = {0x00, 0x02, 0x00, 0x00, 0x00, 0x00, 0x00, 0x01, 0x00, 0x01, 0x00, 0x01, 0x00, 0x01, 0x00, 0x01, 0x00, 0x01, 0x00, 0x01, 0x00, 0x01, 0x00, 0x01, 0x00, 0x01, 0x00, 0x02, 0x00, 0x03, 0x00, 0x00};

    tidcdb7 project application code says all those subclass IDs (OCV, Chem_data_subclass and Resistance_low/high_temp) have 32 bit data, I don't see any reference table for all these subclass in the TRM document..

    Thank you for clarifying and for your time.

    - Andy

  • 0 in reply to Andy Sarangi
    TI__Mastermind 19195 points

    Hi Andy,

    Which file are you referring to from the tida?

    Thanks,

  • 0 in reply to Nick Brylski
    Intellectual 270 points

    Hi Nick,

    It is in WDMM.c. 

    Thank you Nick.

    - Andy

  • 0 in reply to Andy Sarangi
    TI__Mastermind 19195 points

    Hi Andy,

    Many of the gauge internal registers (OCV tables) are not made publicly available. Please go by the TRM for which registers you can access.

    Thanks,

  • 0 in reply to Nick Brylski
    Intellectual 270 points

    OK, thanks Nick.

    We can read, write back and measure BQ27426 we have on our boards, but to my surprise I think we got a wrong part of same footprint on a board that gives us device type as 0400 and firmware code as 0200.

    What device / part # that could be? If we use the standard command that works on the board with BQ27426 we get the following default. Obviously we were not able write new battery info on the board because the register locations are are not same as in BQ27426, when we write and do the soft reset & seal - this board does not save the new battery capacity and other info like other boards do. The Flag & OpConfig registers works on this part.

    It is a BGA part, we can't swap it easily, so it will be nice to know what this part could be? The GPIO pin works and creates SOCI interrupts so it will be good to know what part that we might have received accidentally and what TRM we need to use for this part.

    Thanks for your time.

    - Andy

  • 0 in reply to Andy Sarangi
    TI__Mastermind 19195 points

    Hi Andy,

    It's possible you're not reading the second byte correctly if it's always 00.

    You can test with a baseline (EV2400) to see if it also returns the same thing.

    Best regards,

  • 0 in reply to Nick Brylski
    Intellectual 270 points

    I think we have a defective unit as we don't see this on other boards.. Let's not worry about that for now.

    I wanted to ask you, is there a direct command in the fuel gauge that we can use to find out if the charger is charging or discharging? Is the -ve / 0 current means in the Average current command (0x10, 0x11) FG finds the charger is not charging?

    Thank you Nick for your time and help,

    - Andy

  • 0 in reply to Andy Sarangi
    TI__Mastermind 19195 points

    Hi Andy,

    You could look if the positive current is over a certain threshold to determine if the charger is on.

    Best regards,