We have a smartphone phone design using the BQ24270. We have a removable battery and we would like to be able connect to a USB DCP, swap the battery with a freshly charged one and disconnect from the DCP without the phone rebooting. This requires the BQ24270 Vsys to stay above 3.0 V to prevent PMIC system reset. Most of the time this works ok, but occasionally we observe the Vsys voltage droop to about 2.5V when the battery is removed. This droop occurs before the interrupt is generated due to the battery being disconnected. The droop isn't affected by the load on Vsys and lasts about a msec, which is long enough to cause our PMIC to reset.
I have monitored the input voltage (USB pin) and only see a small transient there (<0.1v)
I have monitored the SW pin and see no switching activity during the falling edge of the Vsys droop.
I have added a fixed resistive load (6 ohms) to Vsys and not seen the droop change. I did this to see if the reset to defaults caused by the battery removal may have caused the BQ24270 to set the USB current limit to 100mA even though we are connected to a DCP 1.5A source.
Do you have any ideas what is causing the Vsys to occasionally droop? Is there any recommended settings that could address it?
If I disable charging (reg 2, bit1) do you think this would resolve the issue?