STM32L452RET6P VDDUSB Pin

[iHamd.1]

Hi all,

I'm using the STM32L452RET6P in my PCB design.

I would like to use its USB Device feature and unlike some other STM32 i encoutered, it seems that here there is a special need in VDDUSB pin on the MCU.

Can someone help me understand how to use this pin when the MCU is the device?

• Do i connect it to VDD?
• Do i connect it to VBUS with a voltage divider?
• Any other options?

Best regards,

Ido

[waclawek.jan]

The main purpose of separate VDDUSB is to provide >=3.0V required for proper working of the built-in USB PHY (it works down to 2.7V but ST calls it "degraded mode" and it's not USB-conformant) in cases when VDD<3.0V. If in your application VDD>=3.0V, using VDDUSB separately would be an unnecessary hassle so it's better to connect it directly to VDD. If your application needs separate VDDUSB, and whatever is its primary source (regulated down to its maximum given in DS, maybe around 3.3V?) you have to make sure it shuts down before VDD (see DS, AN4879 and AN4555).

JW