• State Resolved
  • Locked Locked
  • Replies 2 replies
  • Subscribers 63 subscribers
  • Views 314 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

Original question:

BQ76940: 26 cell management with BQ76940

BQ76940: 20-23S Li-ion battery pack monitor, using 2 stacked IC with different I2C address

Matej
Prodigy 40 points
Part Number: BQ76940
Other Parts Discussed in Thread: ISO1541, TIDA-01093

Hello,

We are working on a battery design where it is required to monitor between 20 to 23 Li-ion cells in series. Due to availability and experience with BQ76940 this is our IC of choice for the design. As BQ76940 can monitor up to 15S cells, we need to use two ICs in a stacked configuration as shown below. To communicate with both ICs over I2C we plan to use I2C Isolator ISO1541 on the top side IC. 

The question that remains is, can we use two different model variants of BQ76940 IC to have unique I2C addressing for both low side and high side IC and if so, can we then remove the FET and MCU control line (as shown in RED on the picture below) to the ISO1541, that is shown in TIDA-01093, as we should be able to uniquely address the BQ76940 ICs?

To have the two ICs with unique I2C addresses we want to select:

  • BQ7694002 with I2C address 0x08
  • BQ7694006 with I2C address 0x18
    TIDA-01093 modified reference

BQ76940 device variants

Looking forward to your reply and opinion.

Many thanks and kind regards,
Matej

  • +1
    TI__Guru* 79213 points

    Hi Matej,

    I think this idea should work. However, I think the control lines may be important for reducing power because the ISO1541 does consume some power. This reference design is fairly complex, so any changes you make should be carefully considered.

    Best regards,

    Matt

  • +1 in reply to Matt Sunna
    Prodigy 40 points

    Thank you Matt for your reply and explanation. 

    We will keep the control line as per the reference design, to allow for low power mode as per your comment. 

    We will also keep the I2C multiplexed, as per reference design, for the first revision to see if using BQ7694002 and BQ7694006 with unique I2C addresses, can hopefully let us address the IC rather than switch between the IC we are communicating to over I2C. If that works well, we may try removing the I2C multiplexing that is described in paragraph 2.4 of TIDUC43A.

    I will be marking this as resolved.