We have some issue concerning STM32H747XIH6 design supplying 1.8V to VDD:
■ Below are some design criterion of this project:
A. VDD is designed to be 1.8V to save power.
A separate 3.3V source is used to supply VDD33USB & VDDA.
B. USB HS function is required.
Our design uses ULPI interface of H747, connected to USB PHY USB3320C-EZK.
USB3320C is configured to run at 1.8V I/O voltage.
■ About the issue:
A. In AN4938 "STM32H74xI/G hardware development", section 2.1.2 (P.8), it is stated that:
Some questions concerning the descriptions in this application note :
1. What is the definition of "associated GPIOs powered by VDD33USB"?
Suppose this corresponds to the following pins?
(These pins belong to USB transceiver, and have a '_u' property in I/O structure described in data sheet.)
PB15-OTG_HS_DP (AF: USART1_RX)
PB14-OTG_HS_DM (AF: USART1_TX)
PB12-OTG_HS_ID (AF: ULPI_D5)
PB13-OTG_HS_VBUS (AF: ULPI_D6)
PA12-OTG_FS_DP (AF: LPUART1_RTS)
PA11-OTG_FS_DM (AF: LPUART1_CTS)
PA10-OTG_FS_ID (AF: LPUART1_RX)
PA9-OTG_FS_VBUS (AF: LPUART1_TX)
(* Listed AF are the alternate functions we intended to use in this project.)
--- If these pins are configured as GPIO push-pull, is output voltage 3.3V or 1.8V?
--- If these pins are configured as alternate function of other controllers (UART, SPI, etc...), is output voltage 3.3V or 1.8V?
2. How about ULPI interface pins (ULPI_NXT, DIR, STP, CK, D0-D7)? Do they operate with respect to VDD33USB, or VDD(1.8V)?
(Pins PB12 & PB13 is especially confusing, as they are pins for ULPI and also pins for OTG_HS_ID & VBUS, which should run at VDD33USB according to the application note.
In this case their voltage will be different to other ULPI interface pins?
Also there are no other pins that has alternate function of ULPI_D5 & D6.
So if the statement in this application is true, it seems like using 1.8V VDD with ULPI function is not possible.)
Hope someone can help to clarify this issue. Thanks in advance!
