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BQ76952: BREG AND REGIN PROBLEM

Stas Kogan
Prodigy 165 points
Part Number: BQ76952
Other Parts Discussed in Thread: BQ34Z100

Tool/software:

Hi All,

I am working with 14S battery and the BQ76952 and i  have an issue with BREG and REGIN, REG1,REG2 

the problem is that i have 0V in those pins and the BQ76952 dosent works and i cannot communicate with it.

in REG18 i have 1.8V so i think there is no damage to the chip.

My B+ Voltage is 43V.

i am attaching my scheme here i would like to hear if there is any problem with that and if so how can i fix it 

  • 0
    TI__Genius 17795 points

    Hello Stas,

    Was the part working/communicating before at any point? Can you also share the rest of your schematic? The BREG/REGIN, REG1/REG2 connections look fine.

    Also depending on your part number, REG1 LDO is not enabled by default. Section 5 Device Comparison Table in the BQ76952 Datasheet can help determine that.

    Best Regards,
    Alexis

  • 0 in reply to Alexis_H
    Prodigy 165 points

    Hi Alexis, 

    yes in the initial start the IC was communicating 

    i have designed a BMS with the BQ76952 and BQ34Z100 and STM32 MCU 

    at first we thought that as seen in the scheme i attached that the MCU is working initially as common collector and maybe forcing the AFE to to reset and we took out the 0 ohm resistors and then i had communication with both IC's but the communication collapsed after some time and didn't came back

    also i have a question about the wake up from TS2 what those it does to the AFE? it makes some reset to the component?

    i am attaching the scheme and the I2C lines





  • 0 in reply to Stas Kogan
    Prodigy 165 points

    does the BJT i picked is appropriate?

  • 0 in reply to Alexis_H
    Prodigy 165 points

    I managed to connect to the bq34z100 fuel gauge i also used but still now REGIN and BREG 

    Is there a reasom for this pins to be pulled down? Meybe something internal? 

  • 0 in reply to Stas Kogan
    TI__Genius 17795 points

    Hello Stas,

    Please give me some time to review the schematic. Exiting SHUTDOWN MODE of the BQ76952 SHUTDOWN Mode FAQ should help explain what waking up from SHUTDOWN mode does. The BJT should be fine.

    Some other questions are:
    1. Did you have CRC enabled? If so, the CRC also needs to be sent.
    2. Can you check REG18 voltage as well? If REG18 is reading ~1.8V, the part is probably still functioning correctly and awake.
    3. Do you have REG0 enabled? REG0 is what drives the base of the external NPN BJT typically using the BREG pin. Section 6.3.1 Preregulator Control talks more about it in the BQ76952 Technical Reference Manual and how to configure it.

    Best Regards,
    Alexis

  • 0 in reply to Alexis_H
    Prodigy 165 points

    Hi,

    I do have 1.8V in REG18 but the problen is that i dont have voltage in REG0 

    I domt have accsses to this chip using this schematic 

    Meybe it is beacuse the I2C of the two components is together? 

  • 0 in reply to Stas Kogan
    TI__Genius 17795 points

    Hello Stas,

    It should be fine for the BQ76952 and gauge to use the same bus as long as they have different addresses. 

    With your current schematic, you won’t be able to use the 3.3V from REG1 to allow for communication with the device. I would recommend first using an external supply for the pull-ups instead so you can try to communicate to the device and configure the device. Can you also try taking logic-captures of the comms as well?

    Best Regards,
    Alexis