BQ77905EVM-707: Doubts regarding BQ7790518 Stacking

Goutam Ghosh

Part Number: BQ77905EVM-707

Tool/software:

Hi,

I am current testing two EVMs of BQ77905EVM-707 for 10S stacked configuration. I have connected the circuit as specified in the EVM. However, I did not connect the D3 and R20 of the bottom device as I dont need any UV recovery. Now the problem is, in the event of an Overvoltage, the top device CHG signal goes low, however the bottom device CHG MOSFET is never high, it always stays low in normal operating condition as well. As in the actual circuit we will use the CHGFET drive of the bottom device to drive our CHGFET, what changes shall I make to make the CHG FET of the bottom device HIGH during normal condition and low during an event of Overvoltage?

7 months ago

0 Goutam Ghosh 7 months ago

Prodigy 100 points

Note : D3 and R20 are the LD pin diode and 470k resistors

0 Luis H. S. 7 months ago in reply to Goutam Ghosh

TI__Mastermind 42060 points

Hello Goutam,

I am not sure why the EVM user guide mentions to wire like this. I would suggest to actually wire the BAT- of the top boartd to the same node of Cell5 of the bottom board.

Did you check all of the voltages around the board to ensure all possible fault conditions/recoveries are met?

Best Regards,

Luis Hernandez Salomon

0 Goutam Ghosh 7 months ago in reply to Luis H. S.

Prodigy 100 points

Yes, all recoveries are met. Can you please give me a proper wiring diagram/schematic of 8S and 6S configuration for protection against only overcharge? I am planning use bq779518 for my 8S and 6S batteries for overcharge cut off only.

0 Luis H. S. 7 months ago in reply to Goutam Ghosh

TI__Mastermind 42060 points

Hello Goutam,

You could leave the DSG FET unpopulated, if you are not worried about the discharge protections.

Best Regards,

Luis Hernandez Salomon

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BQ77905EVM-707: Doubts regarding BQ7790518 Stacking