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BQ77908A: BQ77908 EVM 4S AND 8S

Babu Vishwanath Hemath Kumar
Prodigy 230 points
Part Number: BQ77908A
Other Parts Discussed in Thread: BQ77915, BQ76920, BQ76930

Hello,

I have started my new project with BQ77908A battery protector IC, so I have the following questions in the EVM module of this IC, 

1) According to the cell counts in table 9, of the datasheet it is mentioned a word remove, So I would like to clarify that do we have to desolder those components from the EVM as per our cell count?

2) Does this IC is suitable for I2C communication?

3) I have a plan to control my CHG and DSCHG MOSFET using my MCU, in that case what exactly I should do with the unused pins in this IC like CHG, DSG, CPKN, DCPKN?

4) In the website of TI I am unable to find the EVM product, can you send me the link of this product, I want the link of BQ77908A EVM product?

  • 0
    TI__Mastermind 33000 points

    Hello Babu,

    The EVM is no longer being sold, so it is not possible to obtain the board. 

    Follow the explanation in Section 9.1.6.5 4- to 8-Series Cell Configuration of the datasheet to short cells for lower cell counts. In short you should short starting at the top of the cell stack. A 100-Ohm pull-up resistor is recommended but not needed.

    I2C communication is possible.

    Since you are not using FETs, connect the IC as shown in Section 9.1.6.4 Common Return Path With No FETs of the datasheet.

    This is a very old part, which makes it a bit more difficult to support. I would recommend you look into newer parts, like the BQ77915 or the BQ769x0/BQ769x2 families. 

    Best Regards,

    Luis Hernandez Salomon

  • 0 in reply to Luis H. S.
    Prodigy 230 points

    I would like to know what to do with NC pins of this IC, can I leave them open and 

    Regarding the TS and VTSB pin I am not going to use, so in that case what I should do, Do I leave it open ?

  • 0 in reply to Babu Vishwanath Hemath Kumar
    TI__Mastermind 33000 points

    Hello Babu,

    I do not believe you can leave the TS/VTSB pins open. There's an open and a short TS conditions which can trigger faults. See Section 9.1.4.1 TS and VTSB Pin Interface of the datasheet.

    You want to leave the NC pins floating, as mentioned in Pin Functions of the datasheet.

    May I ask, why do you want to use this part? I would recommend to use a part like the BQ77915 if you are using it for cell balancing purposes.

    Best Regards,

    Luis Hernandez Salomon

  • 0 in reply to Luis H. S.
    Prodigy 230 points

    The reason I am using this IC is, the IC that you mentioned is not available in stocks right now and I also checked with other ICs too all are unavailable and out of stock in both mouser, TI product section and digikey 

    Only this IC is only available that's why I don't have any option left 

    If you think there are stock of any IC that can suit for my both 4S and 8s cell balancing along with I2C communication application

  • 0 in reply to Babu Vishwanath Hemath Kumar
    TI__Mastermind 33000 points

    Hello Babu,

    The BQ77915 has some of its part in stock, maybe one of these can fit your requirements. Although this part does not have I2C support.

    The stock situation with the BQ76920/BQ76930 (which has cell balancing/I2C) is expected to improve significantly during this year. In the long term there should be no issues with the supply of this part.

    Best Regards,

    Luis Hernandez Salomon

  • 0 in reply to Luis H. S.
    Prodigy 230 points

    Yes I can see the difference between these two ICs but issue is I had to complete my first design of product with result by end of this march, that's why I gone for this BQ77908A IC, 

    Do you think Thinking this IC will not be better choice for my application? 

    Can you check my design if possible

  • 0 in reply to Babu Vishwanath Hemath Kumar
    TI__Mastermind 33000 points

    Babu,

    The stock situation of this device may actually worsen over time as this is an older part and most production is moving away from these.

    With the newer parts, the stock situation will improve over time. If you aren't expecting to use many, the stock situation on this part may not be an issue.

    This is a 10 year old part, n ewer parts offer more features, accuracy and have better support.

    Yes, you can share your design through private messages. I will send a friend request.

    Best Regards,

    Luis Hernandez Salomon

  • 0 in reply to Luis H. S.
    TI__Mastermind 33000 points

    I responded on the private messages and will continue there.

    Will close this thread.

    Best Regards,

    Luis Hernandez Salomon

  • 0 in reply to Luis H. S.
    Prodigy 230 points

    Ok thanks Mr. Luis Hernandez