cancel
Showing results for 
Search instead for 
Did you mean: 

How to connect SMPS when it is not used in STM32U545?

leo8
Associate

I'm designing a custom PCB with STM32U545NEY6Q and I don't need to use the SMPS, only the LDO. I'm not sure how to connect the SMPS, I found a post about the STM32H745IIT6, and followed the same procedure, but should I do that? 

I followed the datasheet recommendations and connected the pins as shown in the image below.

Screenshot from 2025-06-17 11-21-57.png

I didn't find a similar version of the MCU without the SMPS, and the MCU dimensions fit my design perfectly. Can you tell me if this connection will work? Or recommend another similar MCU, from the STM32U5 series, without SMPS?

1 ACCEPTED SOLUTION

Accepted Solutions
GET
ST Employee

Hello @leo8 ,

1_ After checking the product selector of the STM32U5 series, it seems all WLCSP56 packages are only available in SMPS internal versions and for 535NE, 535NC and 545NE devices. STM32U5 series - Products
About your Power connections (VLXSMPS, VDDSMPS) , I see it is in line with the recommendation of RM0456:

GET_0-1750233000039.png

You probably let VSSSMPS tied to ground also ?

Please note also these remarks from AN5373:

GET_1-1750233501703.png

Also, as per the AN5766, the STM32U5 will start in LDO mode, and if you don't activate SMPS, there should be no issue:

GET_2-1750233574312.png

2_ Also, please note another point linked to VDD / VDDUSB, which I remarked during my search:

For 535/545 with SMPS, there is a VDDUSB pin (A1 on WLCSP56 devices) , but it seems this pin has been renamed VDD in these WLCSP56 packages and there is discrepancy between AN5373 (mention VDDUSB for all packages with SMPS) Vs STM32U545xx Datasheet DS14216 (second sentence should be " Pin number A1 ...  .... in Table 27 STM32U545xx pin/ball definitions" ) :

GET_3-1750234711366.png GET_4-1750234939996.png

strange also this point : no VDDUSB appears in the power supply overview (without SMPS packages)

GET_5-1750235500295.png

 

Hope this clarifies for your design.

Best Regards,

 

 

View solution in original post

1 REPLY 1
GET
ST Employee

Hello @leo8 ,

1_ After checking the product selector of the STM32U5 series, it seems all WLCSP56 packages are only available in SMPS internal versions and for 535NE, 535NC and 545NE devices. STM32U5 series - Products
About your Power connections (VLXSMPS, VDDSMPS) , I see it is in line with the recommendation of RM0456:

GET_0-1750233000039.png

You probably let VSSSMPS tied to ground also ?

Please note also these remarks from AN5373:

GET_1-1750233501703.png

Also, as per the AN5766, the STM32U5 will start in LDO mode, and if you don't activate SMPS, there should be no issue:

GET_2-1750233574312.png

2_ Also, please note another point linked to VDD / VDDUSB, which I remarked during my search:

For 535/545 with SMPS, there is a VDDUSB pin (A1 on WLCSP56 devices) , but it seems this pin has been renamed VDD in these WLCSP56 packages and there is discrepancy between AN5373 (mention VDDUSB for all packages with SMPS) Vs STM32U545xx Datasheet DS14216 (second sentence should be " Pin number A1 ...  .... in Table 27 STM32U545xx pin/ball definitions" ) :

GET_3-1750234711366.png GET_4-1750234939996.png

strange also this point : no VDDUSB appears in the power supply overview (without SMPS packages)

GET_5-1750235500295.png

 

Hope this clarifies for your design.

Best Regards,