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Vbus leaking into VDD STM32L476

Question asked by Pieter on Sep 30, 2016
I am using a STM32L476 and I have a problem with de Vbus. It starts random to leak into de Vdd. I generate my code through CubeMX

Background: 
I am using a STM32L476JGY6.
VDD-VDDA-VBAT-VDDIO2  running on 1V8
VDDUSB running on 3V 
I noticed when I started my code there is a 50/50 change that the 1.8V Vdd voltage wil jump to 3-3.8V
When this happens is see that there is no current flowing from or to my 1V8 power supply. And everything is drained from the 5V of the USB. When I remove the Vbus, it goes back to normal

Vbus from the USB is directly connected to the uC Vbus pin (E3) (like reference designs from STM)

It only happens when I enable the Vbus sensing in the code through CubeMX. 
What i tried: 
- I added a delay before the USB starts to INIT but it doesn't help.
- lower Vbus  to a lower voltage (3V). Doen't help
- Connecting USB after booting I will have this problem.

When this happens, the USB starts to draw 80mA 

It seems the VBUS pin isn't 5V capable, also not after a stable Vdd. 

Can someone help me out? 

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