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Original question:

bq28z610 FETs Not Initializing

BQ27750: First time initialization of BQ27750

Andrew Ameri1
Prodigy 20 points

Part Number: BQ27750

Hi,

I have integrated BQ27750 in one of my designs. For the past few days I have been struggling with an issue that I was not able to power up my device due to the reason that BQ27750 FETs enable registers are initially initialized as LOW and as the result I was not able to get any battery voltage fed to my system. However, after reading user manuals and forums I realized I can manually enable the FETs using BQStudio. I have a few questions:

1- Why doesn't BQ27750 itself automatically turn the FETs ON when there's a load connected. I initialized all relevant values under "power" tab in BQStudio but I was only able to get the battery voltage out with manually turning the FETs on through BQStudio.

2- How can I make sure the FETs don't turn off anymore?

3- After this initialization through BQStudio and closing the product in an enclosure, if the the device enters one of the protection modes (over current, undervoltage, etc.) due to an abnormal condition and the FETs turn off, would the FETs automatically turn on again if the abnormal conditions are gone? I hope that is the case and we don't have to reinitialize the FETs enable registers again since the product is closed. 

Please advise. 

Thanks,

  • 0
    TI__Guru 52115 points
    The FETs are not controlled by the gauge by default. You need to send a FET_EN command in the bqStudio and then they are under control by the gauge.
    The FETs should be able to turn on again once the abnormal conditions are gone. I would suggest you take a look at Chapter 2 of BQ27750 TRM to see the details.
    Andy