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Original question:

TIDA-010247: Purpose of R112 and R118

TIDA-010247: Function of REG2 for cell balancing?

Abhijith V Narayan
Prodigy 175 points
Part Number: TIDA-010247
Other Parts Discussed in Thread: ISO1640,

Tool/software:

Hello,

Can you please explain in detail how REG2 is used for cell balancing? I have tagged another post asking the similar question above. (Also here).

For the design I am considering not using REG1 and REG2 of both AFEs. Please let me know how is cell balancing related to REG2 as I was not able to understand from the linked post.

Thanks,
Abhijith.

  • 0
    TI__Expert 3860 points

    Hi Abhijith,

    Thanks for reaching out.

    The dummy load(resistor) is connected to AFE REG1/2 to balance the current consumption between AFEs. For example, the top AFE consumes 1mA, but the bot AFE consumes 500uA. You can add 500uA dummy load on BOT REG 2 to balance the current gap.

    BRs

    Kian

  • 0 in reply to Kian Lin
    Prodigy 175 points

    Hi Kian,

    Thanks for replying.

    1. What issues would be caused if the the current consumption of both AFEs are not the same? And the consumption keeps changing between the AFEs always right? How can we size a resistor to match this through all conditions?
    2. I still am not able to wrap my head around the how the two LDO that are for external use is utilized for passive balancing the cells?

    What am I missing?

    Thanks,

    Abhijith.

  • 0 in reply to Abhijith V Narayan
    TI__Expert 3860 points

    Hi Abhijith,

    1. In this design, the IIC isolator ISO1640 has different supply current between different sides. If you use AFE REG LDO to power the ISO1640, it would cause imbalance. The consumption doesn't keep changing. The average value is constant at a stable working condition.
    2. Actually, you cannot call it 'cell passive balancing', it is just for balancing the current difference between top 16s cell module and bot 16s cell module. It is module balancing.
    3. You cannot size a resistor to match all conditions. So I use a isolated power module to power the ISO1640 and DNP the resistor on REG2

    BRs

    Kian

  • 0 in reply to Kian Lin
    Prodigy 175 points
    1. Oh okay. I was confused thinking the REG2 is somehow related to the normal device autonomous cell balancing which did not add up.
    2. Can you please let me know BOT_CB which is coming from the controller is used for? What is the meaning of "Bot stack cell balancing" text mentioned.

    Edit: I just realized I was using the older TIDA-010247 by Ryan Tan which I had a offline copy of. Apologies for the confusion.

    Thanks and happy holidays!

    Abhijith

  • +1 in reply to Abhijith V Narayan
    TI__Expert 3860 points

    Hi Abhijith,

    Thanks. Happy holiday to you too!

    2. The BOT_CB is used to enable the bottom 16s module balancing ie. enable the dummy load. The circuit in your screenshot is also for the power supply of MCU. It is only used to power up MCU at start up. After DC/DC 5V build up, the schottky diode will block the current flow from AFE as the DC/DC 5V_out is set a little higher than AFE REG output.  In general, the diode is used to prevent the reverse current flow into AFE REG pins.

    Yes, I am just released the newer TIDA-010247 which is better suit ESS application.

    BRs

    Kian