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Vbus leaking into VDD STM32L476

pieter239955_st
Associate
Posted on September 30, 2016 at 12:50

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? 

#vbus #current #stm32l476jgy6
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