BQ76920: High Side Charging FET

KIM

Part Number: BQ76920

Hi,

For BQ76920, the driver of charging and discharging FETs are low side.

For charging FET, we would like to have high side. Can we use Pmos Charging FET on high side and the Charging FET is driven by BQ76920 CHG pin as the attached figure?

Discharging FET is still low side.

Thanks,

Kim

over 1 year ago

0 Luis H. S. over 1 year ago

TI__Mastermind 27830 points

Hello Kim,

May I ask why do you want to do this implementation? You could have separate charge/discharge paths low-side on the low-side too. Although for a different device, you could use the bq77905 Separate Current Paths application note as an example.

Now, on to your question. It could be possible to do something like that. However, I would not use a BJT to do this. I would recommend to use a N-Channel FET instead. Additionally, implementing it this way could cause some issues in the turn-off of the FET. Since the turn-off would be determined mostly by the Rgate-source resistance. You would need to implement a turn-off circuit. I gave a more detailed explanation in this older E2E thread:

https://e2e.ti.com/support/power-management-group/power-management/f/power-management-forum/1185634/bq77915-bq77915-high-side-use

Best Regards,

Luis Hernandez Salomon

Power management

Power management forum

BQ76920: High Side Charging FET