Going back to this problem again, the basic problem (and it has not been solved) is that if USB power is not plugged in (to SYS), the MP2672 cannot talk on the i2c lines and worse, it prevents any other device from using the same i2c bus! Reading above again suggests that if we power MP2672 VCC from some other source, then MP2672 could talk on i2c bus even if it cannot charge. Is this correct? But this doesn’t make sense because VCC is generated by MP2672 LDO regulator.
In my PCB, the main power from battery is cut off by a relay, so I have no source of power except a direct battery connection to SYS, which would drain the battery continuously.
Could someone from company please comment?
I pasted schematic here. MAIN
I made a new post about this topic at MP2672 I2C with no USB power since this one went stale.