BQ24190: avoid overdischarge in case supplement mode

Hello Kanji,

See my comments below:

Question 1: 

The SYS current limit cannot be configured on the device. If their concern is over-discharge of the battery, both current and voltage should be monitored. They could use a gas gauge, like the bq27542-g1 that provides voltage and current information of the battery. The host can obtain IV data from the gauge and determine when the BATFET should be disabled to turn off supplement mode.

One thing to notice is that if the BATFET is disabled to stop supplement mode, this means the system will turn off, which is expected as this should occur when the battery is approaching depletion. If this approach is used, I suggest determining a reserve capacity (for example 5% of the battery's capacity) and use the gauge to determine when the battery has this capacity remaining. This capacity should be used to do an orderly shutdown of the system. Once the input adapter is plugged in again, normal charging and operation will resume.

Question 2:

This refers to scenarios, for example, when the user has the ability to swap batteries or the battery might be absent during normal operation. This is when the BATFET should be turned off, otherwise the STAT signal will begin blinking due to it toggling between the "Fast Charging" and "Charge Done" states. 

Kanji Shibatani said:

Please let me know the way to detect the battery for BATFET disable.

Are you referring to normal battery detection or how to detect the battery conditions to determine when BATFET should be disabled. If the former, the STAT signal blinking along with the toggling of "Fast Charging" and "Charge Done" states is a good indicator that either the battery connection is not solid or the battery is missing. If the latter, please see answer to question #1.