STM32H723 - ULPI and pc2_c/pc3_c

[sophie]

Hi all,

I'm currently designing a board that requires using an stm32h723 with USB HS (I need more bandwidth than FS allows). The stm32h723 I'm using doesn't expose pc2 or pc3, which are needed for ULPI DIR and NXT respectively. Instead, pc2_c and pc3_c are exposed as pins on the chip. These are internally connected to pc2/pc3 internally with an analog switch, but is this really sufficient for ULPI? The datasheet doesn't seem to be clear.

The stm32h747 datasheet does specify using ULPI over pc2_c/pc3_c, which makes me think it's at least been considered. I'm curious why it doesn't seem to be specified in the stm32h723 datasheet (either specifying whether it will or won't work)

I did find a few forum posts of people using pc2_c/pc3_c with USB, although it seemed like this had issues (including hardware damage, possibly of the analog switch itself).

Thanks!

[STOne-32]

Dear @sophie ,

STM32H723 was designed after STM32H747 and after discovering the Hardware limitation thru the _C pins to not exceed current of 1mA and try to minimize the usage to original  ADC channels ( Direct path) So we removed from the specification in datasheet. The behavior is exactly the same as H747 . our recommendation if USB high speed thru ULPI is required choosing the UFBGA144 package is the best option to have the PC2 and PC3 exposed .

hope it helps you ,

STOne-32

[sophie]

Thanks. Should this be documented in the datasheet/errata somewhere?

[STOne-32 · Accepted solution]

Dear @sophie ,

Thank you for the follow-up , indeed we need to double check and back shortly .

looking to the Datasheet again , this is possible with that package 

Only Ethernet in MII mode is not supported where it is mentioned by [0/1] , USB High speed with ULPI is fully supported  on all packages either PC2/PC3 or their _C when the switch is active with SYSCFG register

https://www.st.com/resource/en/datasheet/stm32h723ve.pdf

Regards,

STOne-32

[Zhou JianQiang]

Hi @STOne-32 :

Since  PC2/PC3 and their _C can be controlled by the switch in SYSCFG register, when we still need PC2 and PC3 exposed?

[STOne-32]

Dear @Zhou JianQiang ,

as you can see in this MCU STM32H723 the usage is exclusive for a given package . 

 _C pins are initially designed to have direct path for ADC and have best Accuracy on these channels. Now PC2 and PC3 can be used for all digital communication and avoid the current limitation of 1mA that may damage the device .

Hope it helps ,

STOne-32