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BQ77905: Shutdown and Re-enable

Kevin Knicker
Expert 1091 points
Part Number: BQ77905

Tool/software:

Dear TI support,

I am looking into the Shutdown feature on the bq77905.

Looking at the TI slua826 document, Figure 4 shows a method for switching into Shutdown and then enabling the pack again by connecting ENABLE to Pack+ which I assume is handling exterally.

The challenge I have is our customer doesn't have a good way to pull Enable up to Pack+ on the host side.

It is also preferred to have the pack shutdown until a charger is applied.

Is there any possible way of handling that on the battery pack side using this circuit as a starting point?

Perhaps a diode between enable and Pack+? So when a charger is applied it would activate ENABLE.

Any thoughts on this would be appreciated.

Best Regards,

Kevin

  • +1
    TI__Mastermind 42060 points

    Hello Kevin,

    Yes using the charger voltage to turn the BJT ON is definitely an option here. However, that'd need to be constantly applied here in order to keep the device ON. 

    Unless you have an additional circuit that can keep enable high when the charger is gone, this may not fully work.

    Best Regards,

    Luis Hernandez Salomon