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

Nick56152
Intellectual 545 points
Other Parts Discussed in Thread: BQ20Z65-R1, BQ24747, BQ28400, BQ20Z65

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?

 

Thanks in advance to anyone who can help me answer these questions :)

  • 0
    TI__Intellectual 930 points

    Both the bq28400 and bq20z65-R1 work with LiPo batteries and have a broadcast feature that can communicate to a charger through SMBus.

    In terms of the specific chargers you mentioned, you may want to repost the question to the charger forum in order to get a prompt response.

    Regards,

    Viktoriya

  • 0 in reply to Viktoriya Sherman
    Intellectual 280 points

    We are using a battery that has the BQ20Z65-R1 in it.   We occasionally get SMB bus errors in our system.   Our Processor talks to the battery and other devices over the same SMB bus.     I see that the BQ20Z65-R1 has a broadcast mode.  How is this enabled and disabled?   What SMB device memory addresses does it access when in broadcast mode?   

    We suspect that the battery is bradcasting on the SMB bus and causing conflict on the bus.

    John

  • 0 in reply to John Mladenik
    TI__Guru* 76230 points

    Hi John,

    Setting the [Bcast] bit in operation  cfg B register in the data flash enables broadcast. The bq20z65 uses slave address 0x16 on SMB for communication.

    Refer to section 2.5.1, 2.11.2 , 2.11.3 and 2.11.4 of the technical reference manual of the bq20z65 (this can be found on TI's website) for additional info as regards packet error checking and broadcasting.

    thanks

    Onyx