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BQ25570: USB VBUS issue

Part Number: BQ25570
Other Parts Discussed in Thread: BQ25173

Hi,

We have recently designed a project that uses BQ25570 to harvest power from a solar panel (not currently connected), outputs a regulated 1.8V from a v_bat coming from a supercapacitor. We also have a supercapacitor charger that uses USB to charge up the device.

EN pin on BQ25570 is pulled high using VBUS so that everytime the device is connected to USB, we disable BQ25570 and charge up the supercacitor.

The problem is that as soon as we plug USB in, the supercapacitor charger BQ25173 goes to smoke! With or without supercapacitor (v_bat) connected. 

Is there anything obvious from the attached schematic that leads to this catastrophic failure?

Thank you for your review time!