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BQ79616EVM-021: BQ 79616 and 79656 USB2ANY stack connection

Part Number: BQ79616EVM-021
Other Parts Discussed in Thread: BQ79656EVM-021, USB2ANY, , BQ79616

Hello!

Is it possible to use USB2ANY and BQAutoEval to connect BQ79616EVM-021 BQ79656EVM-021 in stack as on picture below?

  • Hello Dagmar,

    Yes, this is possible. We do it this way on the EVM

  • Are there any specific conditions that need to be set when starting BQAutoEval? Whenever I set stack  device to BQ79616 or 79656 and the  bridge device to BQ79616 or 79656 (in any avaliable configuration), only the bridge device wakes up and auto-adressing freezes without success.

  • Dagmar,

    I managed to get it to work on the bench. The autoaddressing wasn't working at first, but I tried again and it found the second device. Yes, the GUI is not optimized for mixing these devices without a BQ79600, but I do believe it is possible as shown below.

  • Hello!

    Thanks  for the replay, i got it working, the problem was power supply connection. I did connect the eval boards as i would to the battery (the top board GND <-> lower board VSTACK). Then connecting both Vstack to power supply and both GND together is is working well.

    For my clarification for the BQ796xx to talk to each other with different supply voltages separation transformer not included with the kits is needed? Or is it possible to make it work with already mounted components?

    Thanks for reply.

  • Hi Dagmar,

    Sorry for the delay in response. Hopefully, everything is working properly now. The BQ7961x family supports stacking power supplies in the method you described with the GND of the top board and VSTACK of the bottom board connected. In typical applications we will see transformers used on the VIF when going from PCB to PCB but capacitor or capicator + choke isolation when the ICs are on the same PCB. In a low noise EVM environment I would expect that there should be no issue with the currently populated isolation type (this is what I use in my setup most often). Please let me know if you are still having issues and I would be happy to help you debug.

    Thanks,

    Geoff