Which LDO/Buck from STPMIC25A can be used with SD card boot?

[DMårt]

• Hi!

I accedently used STPMIC25A instead of STPMIC25D when I want to boot A35 from SD card.

According to AN5727 page 13, topic 4.1.8. it says that if the MP257 is going to boot from SD card, then the STPMIC25D must be used instead of STPMIC25A due to LDO7 and LDO8 are dedicated for 1.8/3.3V at initial boot.

My question is: is there any soldering fix I could use to borrow voltage from another Buck/LDO output from STPMIC25A?

My goal is just to boot TF-A. 

Suggestion:

I use LDO2 for VDD_SD and VDDIO_SD. LDO2 boots at 3.3V. My SD-card might be UHS-I, but I'm guessing that it can run at low speed as well (3.3V pull-up).

Edit 1:

I cut of the traces from VDD_SD and VDDIO_SD and connected them to LDO2. Now I have 3.3V on the SD Card and its pull-up. But no signs of output of the USART6.

The CLK of SDMMC1 has been started. I guess that the BootROM understand its purpose when telling 0b0001.

[PatrickF]

Hi @DMårt 

you might 'transform' an STPMIC25A in STPMIC25D by reprogramming it's NVM. That's could be possible by with https://wiki.st.com/stm32mpu/wiki/STM32PRGFW-UTIL and CubeProgrammer (which does not need SD card supply).

About the boot issue itself, you could try using https://wiki.st.com/stm32mpu/wiki/STM32_MPU_ROM_trace_analyzer#On_STM32MP2_series (need USB + UART)

Regards.