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Original question:

BQ77915: BQ7791500

BQ77915: For the BQ7791500 to recover from UV fault, does it absolutely need to detect load removal?

Bill Crandall
Prodigy 10 points
Part Number: BQ77915

For the BQ7791500 to recover from UV fault, does it absolutely need to detect load removal?

In the datasheet, "9.3.2.2 Operation in UV" section, it seems to indicate it can recover after a delay without load removal:

9.3.2.2 Operation in UV

A UV fault detection is when at least one of the cell voltages is measured below the UV threshold, VUV, for a duration of a UV delay, tUVn_DELAY. The DSG FET is turned off.

The UV fault recovers when:

• The voltage of the cell in fault goes above the (UV threshold + UV hysteresis, VHYS_UV) for a time of a UV delay OR

• The voltage of the cell in fault goes above the (UV threshold + UV hysteresis, VHYS_UV) for a time of a UV delay and the load is removed.

We intend to use the BQ7791500 in a device where the user cannot remove the pack. We could 'fake' a removal by briefly grounding LD, but would rather not.

Thanks!

  • 0
    TI__Guru 54715 points

    Hi Bill,

    The BQ77915 has options for how it recovers including voltage or voltage and load removal. The data sheet Specifications and Detailed descriptions sections will describe all versions.  For specific configurations see section 6 Device Comparison Table. 

    Yes the BQ7791500 requires load removal for UV recovery.  Many power tool users like the feature so that if a user runs to the tool to UV and does not release the trigger the tool does not re-start unexpectedly when the voltage recovers.  If the system maintains a slight load whether the trigger is pulled or not, or the battery is removed or not, a charger may need to be attached to cause recovery for this part.   Perhaps charger connection is an alternative to a special circuit to temporarily ground LD.