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BQ24770EVM-540: SMBUS pull-up voltage for NVDC Charger + Gauge EVM setup

Carl Olen
Expert 1160 points
Part Number: BQ24770EVM-540
Other Parts Discussed in Thread: EV2400, BQ24770

I’m close to turning on my experimental setup. But before I do, I had some questions.

I’m using the bq24770EVM and the bq40z50EVM in an NVDC charger + gauge setup. The attached diagram shows how I plan to hook it all up, based on what I read in the two EVM user guides. My questions are as follows.

1.)     If I need to use a second 3.3V power supply for the bq24770EVM, which I assume is the pull-up voltage for the SMBUS, should I wire this same 3.3V to J2 of the bq40z50EVM (which would normally be where VOUT1 from the EV2400 comes in)? Please see the dashed orange connection in the diagram.

2.)     Why doesn’t the bq24770EVM have the same 4-pin header for its SMBUS input as the cable to the EV2400 suggests?

 

Please let me know. Also, please confirm that this hook-up is correct and ready to power up and test.

Thanks,

Carl OlenNewBatteryConcept_EvaluationSetup2.pdf

  • 0
    TI__Genius 11850 points
    Hi Carl,

    I only support battery chargers, not gauges, but your setup looks correct. Your PS1 power supply does not need such a high current limit of 10 A though, so it's possible to set a lower current limit. To answer your questions:

    1) Yes, the dashed orange connection should be fine if you need a 3.3 V supply for both EVMs.
    2) Unlike some of TI's other battery charger EVMs, the BQ24770 EVM does not have an LDO that provides a fixed 3.3 V pull-up rail for several pins on the IC. Therefore, the 4-pin header is not used on the BQ24770 EVM because it needs to have a connection available for an external 3.3 V supply to provide this pull-up rail.

    Best regards,
    Angelo