Hello,
We are working on a beaglebone reference design based platform that has a am335x sitara + TPS65217 PMIC + BQ27621 battery gauge.
While trying to place our platform in "standby" mode where the entire system is shutdown and a boot can be triggerred by the PMIC pushbutton, we discovered that we had mistakenly tied the LDO output of the battery gauge to the VDD_1V8 LDO3 output of the PMIC.
Because of this, we see that even with the system in fully shutdown with battery connected, there is a current consumption of around 10mA which will kill our product's shelf life. Unfortunately, we have already produced multiple PCBs with this issue.
Through experimenting, we have discovered this:
1. Modding the PCB to 'cut' the connection between PMIC LDO3 (vdd_1v8) and LDO of battery gauge, we are able to see that the platform consumes much less current. With the system fully shutdown, we still see the battery gauge LDO output at 1.8v
2. Without the mod, even if I place the battery gauge into shutdown or enable hibernate bit with explicit i2c commands before shutting down the system (halt command in linux), I see that the LDO output of the gauge is at 1.8V. Current consumption is at ~10mA. My only conclusion when comparing it against the previous case is that the PMIC, even in it's OFF state, is loading the battery gauge LDO and drawing the 10mA current.
We are trying to determine if there is a way for us to fix this in software. Can you tell if the LDO n the battery gauge can be shutdown/disabled with i2c commands? If this is possible, then this would mean the PMIC won't be drawing any power through the battery gauge LDO. We would be able to avoid having to mod numerous PCBs that have been manufactured with this issue.
cheers,
Arun
