Help on a schematic for dev-board based on STM32G431 with USB-C power delivery and programming features

[Vincenzo Gibiino]

Hello,

I am making a dev board for this new family of MCU, I need USB programming and power delivery.

To make it I am referring to the datasheet, Nucleo dev board and to the application note.

I did only once a board with STM32 and it was an F1. I can see that there are many differences, so I thought to open a topic to gather some more suggestions.

This is what I have so far: high quality pic of the schematics

1) Pull up for DP

Back in the F1 boards I had to put a pull-up 1.5k resistor between DP and 3.3V, now it seems that the needed circuit is already provided inside the package. Si I can remove R1, R2 and R5. Is it correct or did I misunderstood it? What about the 2 cap (C13, C14)?

2) CC1 and CC2 pins for power delivery

Should I wire the CCx to UCPD1_DBCCx or to UCPD1_CCx? Which is the difference?

3) VREF pin usage

I can have this pin connected to VDDA or to an external source (plus 2 cap):

"If JP2 is closed then C10 and C11 doesn't have to be populated"

4) BOOT0 pin wiring

I think I should wire this pin to GND for normal operation and to 3.3V for uploading of new code. I think I would do it with a header-jumper but other suggestion (or correction) are welcomed

5) GND and AGND connection

I think that I would get different answer on this. I saw a lot of people making a single GND/AGND and also someone make a single point connection between them

I would like to share the schematics/board if you think it would be useful

[TDK]

> 1) Pull up for DP

You can remove everything on that line. If you want additional ESD protection, put a dedicated chip on the data lines for that. Take a look at AN4879.

https://www.st.com/resource/en/application_note/dm00296349-usb-hardware-and-pcb-guidelines-using-stm32-mcus-stmicroelectronics.pdf

> 3) VREF pin usage

Typically this is directly connected to VDDA. Same notes as in (5) below.

> 4) BOOT0 pin wiring

If you're programming over SWD, you can hook this straight to GND. Only reason you need to pull it up is to enable the system bootloader.

> 5) GND and AGND connection

If you're not using the ADC/DAC or if you don't need more than about 10 bits of precision, it doesn't really matter how you ground AGND. I put a via to the ground plane right at the pin.

[Vincenzo Gibiino]

I just updated the question with a pic of the last schematics, as @TDK​ suggested.

> 1) Pull up for DP

I removed all the resistors on the DM/DP lines but I keept the two capacitors, should I remove also them?

> 3) VREF pin usage

I would do as you suggest and I will keep the JP2 closed, also this is the same as the reference design from STM

> 4) BOOT0 pin wiring

I would mainly use the bootloader so I would need to switch in a simple way the BOOT0 pin

> 5) GND and AGND connection

10 bits would be more than enough, I will be using the common GND

If you still have any suggestions please I will follow

EDIT: found the solution for the CCx pins here. I think I will implement the TCPP01 in my design