STM32F and USB at 1.8V

[sburr]

Posted on November 16, 2015 at 18:54

I would like to connect an STM32F405 to usb while running the chip at 1.8V. Since USB requires 3.3V I need some kind of level translator. I have tried the TSX0102 and did not get it working. Has anyone done this before or could recommend a level shifter chip for USB?

[Tesla DeLorean]

Posted on November 16, 2015 at 19:04

Are you sure this is a remotely practical approach?

Have you considered the

http://www.st.com/web/catalog/mmc/FM141/SC1169/SS1580/LN1840/PF260095?icmp=pf260095_pron_pr_feb2015&sc=stm32l476-pr

, the L4 has a specific VDDUSB pin to deal with this issue.

[sburr]

Posted on November 17, 2015 at 17:27

We don't want to switch processors for many reasons, I would like to run an STM32F405 on 1.8V and still have USB capability. There is nothing in the 405 datasheet about how the usb phy works, is it just push pull?

[Tesla DeLorean]

Posted on November 17, 2015 at 19:29

The pins have specific drivers for the USB bidirectional/differential requirements that meet the USB specs. I think the advice in the past is to increase your supply voltage when you expect to be using USB. I don't think ST has made representations that the USB PHY will meet specs at lower voltages.

Perhaps the External PHY mode offers some additional flexibility, but I'm hard pressed to see that some external auto-direction converters are going to get the job done on the regular pins. What's available is likely highly specialized, and expects more control signals than you can deliver.

http://www.ti.com/lit/ds/symlink/sn74avc2t872.pdf

Your best bet is to talk with your ST FAE about this.