When i power on the board with BOOT0 pin to 1 the micro goes in BOOT mode (I think) but an infinite NRST reset loop is triggered every 30 milliseconds with a duration of 20 microseconds. Can you help me? Magnani

[HTitalia]

i am using an STM32L4R9ZGJ6 

[Uwe Bonnes]

Check option bytes is hardware watchdog is enabled.

[HTitalia]

Thanks for the answer, i checked the OPTR register but the hardware watchdog is disable, all option bit are right

[Uwe Bonnes]

So check you schematic fot logical errors and your board fort shorts and opens.

[Tesla DeLorean]

VCAP pins and capacitors

VDDA

OSCOUT