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bq24725 and bq20z45-R1 operating without host controller

Kjell Ramberg
Expert 1375 points
Other Parts Discussed in Thread: BQ20Z45, BQ24725, BQ20Z45-R1Dear all, I plan to test a setup according to SLUA608 where a bq20Z45-R1 EVM is Connected to the SMBus of a bq24725 EVM. Is it possible to connect the EV2300 to the same SMBus to be able to monitor data flow using either the bq Evaluation software for the bq20z45 or the sw for the bq24725 ? Any comments from those who have experience using a smart charger under the cotrol of the gas gauge IC are very much appreciated. Best regards Kjell
  • 0
    TI__Guru* 76230 points

    Hi Kjell,

    You might have bus collisions doing this since the EVSW acts as a sort of master.

    thanks

    Onyx

  • 0
    Prodigy 180 points

    Kjell:  I don't think you'll have any issues, save one, with this bus topology as I2C/SMBus is open-drain.  My one caveat would be if you are programming a new ROM or DFI to the bq20z45-r1, you can brick the IC if another master on the bus transmits.    If the bq20z45 is the only master on the bus with the 24725 as a slave, you shouldn't have issues.  And by "bricking the IC", I mean that the unseal key is written with an unknown value and if the IC comes back up sealed, you'll have to brute force guess the unseal key.

    Good luck.

  • 0 in reply to Onyx Ahiakwo
    Expert 1375 points
    Hi Onyx Thanks for a quick answer. I see your point - and that was what I feared. But I will try anyway and inform about the result at the forum. Best regards Kjell
  • 0 in reply to Joe Stark
    Expert 1375 points
    Dear Joe, Thanks for taking your time to assist. The bq20z45 would be the only master and I would be very carefull doing nothing than monitoring that the function of the ba20z45 and the bq24725 is according to the DF settings etc. The idea is to use this combination to have a battery with a smart charger in the same pack and use an ac adapter to charge. In this Application it is impossible to have the SMBus available other than "internally" in the battery - but I have Access to two wires which will be the + and - from the ac adapter. Being able to have the bq24725 as a smart charger which is controlled by the bq20z45 according to the JEITA standard is the goal. Then we can fast charge the battery in a safe manner. The Application is a subsea instrument. By the way, - I will inform the forum about the result. If this works fine it might be something that others find interesting. The reasom for letting this post still be open is if anybody else would like to comment Thanks again Best regards Kjell