BQ77915: problem with Discharge FET driver line

Vijay Kumar M

Part Number: BQ77915

Tool/software:

Hello Iam using BQ77915 to balance cells in a 3 cell battery. When one of the Cell voltage goes below Under Voltage (2.7V), the discharge FET driver line goes low, but when the Cell voltage goes above UV + V hysterisis (2.7+0.8V = 3.5V), the discharge driver line does NOT go high...... What could be wrong?

1 month ago

0 Luis H. S. 1 month ago

TI__Mastermind 34930 points

Hello Vijay,

Did you check that all recovery conditions are met according to Table 9-5. Fault Condition, State, and Recovery Methods of the datasheet?

Was the load removed?

Best Regards,

Luis Hernandez Salomon

0 Vijay Kumar M 25 days ago in reply to Luis H. S.

Prodigy 20 points

Yes. The under voltage condition was changed. 2.7V was restored to 3.7V. And the load was removed by pulling out the load connecting wires. But the Discharge line did not come ON. The load was a LED with resistor in series drawing 20mA.

I read in a tech chat which said 'load removal' means connecting a charger. I connected the charger and the discharge line turned ON.

Following link gave the above said info:

e2e.ti.com/.../bq77915-load-removal-charging-to-recover-from-uv-fault

I do not think ' load removal ' can be equated to connecting a charger.

Kindly guide.

0 Luis H. S. 23 days ago in reply to Vijay Kumar M

TI__Mastermind 34930 points

Hello Vijay,

What is the voltage of the LD pin? There should not be a need for a charger attached.

Can you share your device's schematic?

Best Regards,

Luis Hernandez Salomon

Power management

Power management forum

BQ77915: problem with Discharge FET driver line