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"Non-host control" SMBus Charger System (w/ bq20z65-R1)

Nick56152
Intellectual 545 points
Other Parts Discussed in Thread: BQ24747

[I originally posted this question in the Gas Gauge forum]

 

I've been using the bq20z65-R1 for quite some while as an in-system 3-cell LiPo protector - I am now however looking at adding an on-board charger to my design.

After reading http://focus.ti.com.cn/cn/lit/an/slua533/slua533.pdf it seems that this can be done without a host (i.e. microcontroller) - [much simpler!] :)

Question:

Is the BQ24747 charger suitable to be used with the bq20z65-R1 in this "no-host" configuration?

If so, are there any critical design issues I should be aware of?

As a side question (for a diff design): Could the BQ28400 (2-cell gas gauge) be used with the BQ24747 charger in the same "no-host" config?

 

Again, thanks in advance to anyone who can help me answer these questions :)

  • 0
    TI__Guru 56650 points

    An application note may help you: http://www.ti.com/litv/pdf/slua533   To summarize, you can use a standalone charger with a gas gauge

  • 0 in reply to Wang5577
    Intellectual 545 points

    Thanks - that's actually the application note I mentioned in my original post :)

    I just wanted to confirm whether it was for only specific GG/charger combinations though?

    Are all TI gas gauges and chargers with the SMBus interface SBS compatible?

    So the bq20z65-R1 or the BQ28400 GG with the BQ24747 charger will be OK?

     

    Thanks again!

  • 0 in reply to Nick56152
    TI__Guru 56650 points

    The application note describes the gas gauge IC modification. I think the gas gauge IC needs:

    1. Broadcast mode

    2. The command format must match bq24747.

    3. Be able to send charge voltage or current command in 175s continually.

    4. The gas gauge IC need to send different current settings for different conditions: pre-charge current; fast-charge current; temperature shut down or termination current.

    5. The battery pack can be wake up (gas gauge IC can send commands out) under 5.5V because the  wake-up source for that application is 6V (VDDP).