BQ25750: The over current limit when switching from adaptor to battery

Hello Rannie,

Rannie Zhou said:

What's the current limit when the power source switch from adaptor input to battery? Is it 8A?

Yes, the limit is 8A during the power path switchover.

Rannie Zhou said:

How BQ25750 detect this over current issue? Is the peak value or average value be detected? Is the current detected by sense resistor between Vsys and Vbat?

The BQ25750 detects the peak value of the current with the battery current sense resistor.

Rannie Zhou said:

Is there any way to lower the surge current when switching? Such as adding some buffer circuit on the gate pin of MOSFET to lower the turn-on speed and the surge current?

Yes, there's multiple ways to reduce the surge current when switching.

Yes, a buffer circuit on BATFETs will reduce the surge current.

The customer can also connect the FETs to the other side of the current sense resistor to bypass the 8A protection.

Rannie Zhou said:

The issue my customer meet is they found the MOS will turn-off when switching from INPUT to BAT. Whether it's because the current limit of BQ25750 is triggered?

The charger behavior the customer is seeing is probably because of the current limit of the power path.

Just for reference, here's the FAQ on the BQ25750's power path switchover.

Best Regards,
Ethan Galloway