Opening a new issue here because the original issue MP2672 - I2C comms with power disconnected went stale.
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 IN), the MP2672 cannot talk on the i2c lines and worse, it prevents any other device from using the same i2c bus!
Reading the other post 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. Same for SYS, it seems to be generated by MP2672 internally.
In my PCB, the main power from battery is cut off by a relay, so I have no source of power for MP2672 except a direct battery connection to IN, which would drain the battery continuously and even more stupid, it would try to charge the battery from itself, which doesn’t make sense.
Could someone from company please comment? The VCC and SYS pins are somewhat cryptic. Can they (in particular VCC which presumably powers the IOs and i2c circuits?) be potentially powered from some other source in parallel with internally generated power?
I pasted schematic here. MAIN is coming after my power relay. I can only use the MP2672 in standalone mode. How can I use it in host control mode?
Thanks for any updates to this apparent bug in the chip.
