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TIDA-00792: BQ78350+BQ76930+BQ76200 BMS design (TIDA-00792) Current Consumption Issue

Hasan BILIR
Prodigy 30 points
Part Number: TIDA-00792
Other Parts Discussed in Thread: BQ76930, BQ76200, BQSTUDIO

Hello,

WE Designed the 8S BMS using that components. Design almost same with "">www.ti.com/.../TIDA-00792", current consumption from the bat pin of Battery which one is the supply current of the ic's i measured 5.4 mA. Also, the gauge ic into the sleep mode then ı measured 4.5 mA. When i checked the ics' datasheet current consumption must be less than i measured . dou you have any suggestion for the reduce current consumotion?

Best Regards,

Hasan BİLİR

  • 0
    TI__Mastermind 19260 points

    Hi Hasan,

    Could you share your schematic for me to check?

    You may also be seeing the current drawn from the LEDs on the gauge if you've included those.

    Regards,

    Max Verboncoeur

  • 0 in reply to Maxwell Verboncoeur
    Prodigy 30 points

    Hi Maxwell,

    could you share your email addresses or any private places for schematic

    Measured current doesn't include SoC LEDs. 

    Regards, 

    Hasan

  • 0 in reply to Hasan BILIR
    TI__Mastermind 19260 points

    Hi Hasan,

    I've sent you a friend request on E2E. Once you accept you will be able to privately share your schematic with me through E2E direct messages.

    Regards,

    Max Verboncoeur

  • 0 in reply to Maxwell Verboncoeur
    Prodigy 30 points

    Hi Maxwell, 

    İ sent you a direct message. 

    Regards, 

    Hasan BİLİR

  • 0 in reply to Hasan BILIR
    TI__Mastermind 19260 points

    Hi Hasan,

    For my understanding, where and how on the schematic are you taking these measurements?

    Regards,

    Max Verboncoeur

  • 0 in reply to Maxwell Verboncoeur
    Prodigy 30 points

    Hi Maxwell, 

    I take the measurement from Cell8 connection using ammeter this pin also source of the power of the PCBA. 

    The power consumption on the other pins(Cell1...cell7) was ignored.

    Regards, 

    Hasan BİLİR

  • 0 in reply to Hasan BILIR
    TI__Mastermind 19260 points

    Hi Hasan,

    R51 and R61 are both recommended to be 10Mohms. If the FETs are turned on, this might explain the higher than expected current.

    Regardless, I recommend updating these to the recommended value.

    Regards,

    Max Verboncoeur

  • 0 in reply to Maxwell Verboncoeur
    Prodigy 30 points

    Hi Maxwell, 

    Replaced the R51 and R61 with 10Mohms. Current consumption doesn't change. 

    Regards, 

    Hasan BİLİR

  • 0 in reply to Hasan BILIR
    Prodigy 30 points

    Hi Maxwell, 

    Also, wondered about TIDA-00792 EVM current consumption. Do you have any knowledge about it?

    Regards, 

    Hasan BİLİR

  • 0 in reply to Hasan BILIR
    TI__Mastermind 19260 points

    Hi Hasan,

    I'm not too familiar with the TIDA's current consumption. 

    You may want to try measuring each individual IC's current consumption to see which is responsible for the higher IQ. You may also want to check that the gauge's LED pins are not trying to output at all.

    Regards,

    Max Verboncoeur

  • 0 in reply to Maxwell Verboncoeur
    Prodigy 30 points

    Hi Maxwell, 

    Disassamble the FB14 on the schematic whic is the regout 3.3V. i measured current 2mA. in this way, i measured Bq76930 IC power consumption. 

    Regards, 

    Hasan BİLİR 

  • 0 in reply to Hasan BILIR
    TI__Mastermind 19260 points

    Hi Hasan,

    2mA sounds very high for just the bq76930. Could the bq76200 be drawing a portion of that as well?

    Regards,

    Max Verboncoeur

  • 0 in reply to Maxwell Verboncoeur
    Prodigy 30 points

    Hi Maxell, 

    ,Yes that's true.Still,  Power consumption are too much. mentioned datasheet measured power consumption must be uA. it's been a long way we couldn't find any solutions. Dou you have any recommendations? 

    Also, I have another problem which is related to with BQ76200. The problem is when tha battery pack waitng for storage under room conditions after a while battery pack output was measured ~2.5V. we realized that situation on the battery pack we disassembled the battery pack and measured the cell 28V. Also, i check the interface on the battery management studio. There is nothing related to with this. Then, we charged the battery pack and measured the output 33.5V. this situation repeated again after a day later. it was happen again other battery pack. when we disassamble the battery pack i measured the chg and dsg fet gate to ground voltage near 3V but gate to source voltage near 10V. here is a problem with reference i think. when i check the PCBA ground refernece pins there was nothing. we couldn't observed other battery packs. I suspend this situation related to with overload or short circuit situation.

    Regards, 

    Hasan BİLİR

  • +1 in reply to Hasan BILIR
    TI__Mastermind 19260 points

    Hi Hasan,

    I would recommend measuring the voltage across the input resistors of the ICs with an accurate DMM and calculating the current that way. It will be easier to check specific points on the schematic as opposed to using an in-line current meter.

    Some good points to check would be R48, R76+R77, R69+R70, and R45. Replacing R36 with a 100ohm and measuring it as well as changing out FB32 with a resistor to measure the current could also help.

    I checked around internally and there is no spec for the overall current consumption of the TIDA, so it's difficult to say if your total current is unusual or not.

    Regarding the bq76200, could you provide a little more clarity? Is my understanding correct that the FETs are not turning on correctly? Are the gate to source resistors on the FETs in these packs changed to the recommended 10M?

    Regards,

    Max Verboncoeur

  • 0 in reply to Maxwell Verboncoeur
    Prodigy 30 points

    Hi Maxwell, 

    I will try yor recommendations today and i will give you an information. 

    Yes gate to source resistor 10M.

    BQ76200 problem is battery working nice 2-3 times after that battery output measured ~2.8V then we charged the battery one or two second battery output was opened and measured the ~33.4V after a while (one or two hours later) output of the battery ~2.8V. Disassambed the PCBA and checked the parameters of BQ76200  Chg, DSG out, Vddcp out. there was nothing unusual but i measured gate to ground voltage of DSG and CHG FETs `~3V. I was suspended from BQ76200 and i changed. But the problem repeated again. it happens 2 battery blocks. also i checked the BQstudio and there was nothing unusual. Could you examine the schematic again?

    Thank you for your helping, 

    Regards, 

    Hasan BİLİR

  • 0 in reply to Hasan BILIR
    Prodigy 30 points

    Hi Maxwell,

    I tried your recommendations and i measured R36 5mV, R48: 100mV and R76,77: 4mV R69,70: 4mV and also find out out a  one problem which is the D23 zener diode connection. Now, our current consumption value is 2.9ma. is that enoug value for battery pack system ? 

    Regards, 

    Hasan BİLİR 

  • 0 in reply to Hasan BILIR
    TI__Mastermind 19260 points

    Hi Hasan,

    Regarding the bq76200, measuring the gate to ground could be pulling down the voltage at the gate. The charge pump is not very strong, and we've seen cases where a probe can pull the voltage down. It would be better to measure the gate to source voltage. You might want to check if the bq76930 is commanding the bq76200 to turn the FETs off by measuring the bq76930's output pins.

    1mA through R48 sounds very high still. The typical supply current of the bq76200 is 40uA. You might want to check all of the pins on the bq76200 to see where that current is flowing to. It could be that the IC is damaged in some way.

    Regards,

    Max Verboncoeur