STM32H7x: Register PWR_CR3, Bit USB33DEN

Torsten Aurich · ‎2017-11-21

Posted on November 21, 2017 at 10:30

Hello Community,

in the STM32H7 power control i can find the bit USB33DEN in the

register PWR_CR3. As the reference manual explains with this bit

i can enable/disable the VDD33USB supply voltage level detector.

Can anybody explain me what functionality is behind this bit?

What did the VDD33USB supply voltage level detector have?

Did the VDD33USB supply voltage level detector generate an enable

signal to the USB transceiver?

Best Regards

Torsten

#stm32h743 #stm32h7 #usb #pwr-control #usb33den

Khouloud GARSI · ‎2017-11-21

Posted on November 21, 2017 at 17:14

Hello

torsten.aurich

‌,

The USB transceivers are supplied from thededicated VDD33USB supply; whichcould be provided either by the integrated USB regulator or by an external USB supply.

Whenthe VDD33USB is provided from the USB regulator,itssupply level detector shall be enabled through USB33DEN bit in PWR_CR3 register.

The s

upply level monitor guarantees that the VDD33USB is in the right range that allows correct operation of USB Tranceivers.

Khouloud.

Torsten Aurich · ‎2017-11-28

Posted on November 28, 2017 at 11:19

Dear Khouloud,

thank you very much for your answer. But i have one more question.

You have written, when VDD33USB is provided from the USB regulator

(which means for me, the USB regulator is enabled and converts the

higher input voltage on VDD50USB to VDD33USB 3.3V), its supply level

detector shall be enabled through USB33DEN bit in the PWR_CR3 register.

So the supply level monitor guarantees that the VDD33USB is in the

right range that allows correct operation of USB Transceiver.

So my question is, why must i enable the supply level monitor, if i have

USB regulator bypassed because using Nucleo-H743ZI?

Regards

Torsten

Khouloud GARSI · ‎2018-01-04

Posted on January 04, 2018 at 10:43

Hi Torsten,

You should enable the supply level monitor even if the USB regulator is bypassed.

As I said previously, it guarantees that the VDD33USB is in the right range that allows correct operation of USB transceiver.

Best regards,

Khouloud.