Other Parts Discussed in Thread: CC85XXDK-HEADSET-RD
Hi,
I'm using the BQ25015 in a simple charge/supply application, where it is powering a small MCU (3.3V nominal) and charging a 250mAh LiPo pouch cell.
I'm wondering about how to handle the EN input. Obviously it must be set HIGH for the DC/DC to start up, I've looked at the CC85XXDK-HEADSET-RD and here EN is driven high both from VBAT but also from VBUS if connected. The reference design has a small circuit that inhibits EN in precharge (through a 74AHC1G32, STAT1 ORd with STAT2 output). The OR gate is supplied from VBUS, so EN would be pulled high to +5V (or thereabouts).
However, the absolute maximum input voltage for EN is Vout + 0.3V. If I'm not mistaken, Vout is the charger output voltage, which is 4.2V at charge termination and can be much lower depending on the charge state of the battery. So, would not connecting EN to VBUS violate this constraint?
Please help shedding some light on this. What am I missing?