STM32H573VIT3Q - Vcap pins have no voltage

[Amit_En_C]

Hello Everyone :)

I have designed a custom board using STM32H573VIT3Q MCU. when I connected it with st link, the st link didn't recognize it.
After I checked the voltages on the power pins, I saw all the power pins were normal except the VCAP pin (not outputing voltage at all..about 50mV).

The Vcap capacitors P.N is (Digikey) : 490-GRM155Z71A225KE01DCT-ND

Attached schematic for more information.
Please your help.

(Note, FB1506 is a mistake, and is not assembled). 

Thanks alot !

[Amit_En_C]

Update:

1. I disconnected R1502.

2. Assembled R1501.

3. Assembled L1500.

In other words - I choose the SMPS mode. (instead of the LDO).
Works like a charm.

If anyone has an idea why the LDO mode didn't work - please your advice (To help people who will have same question in the future ;)

Thanks,

Amit.

[KDJEM.1]

Hello @Amit_En_C  and welcome to the Community;

Could you please refer to AN5711 precisely Figure 5. STM32H563/H573 power-supply scheme with SMPS and Figure 16. STM32H573 reference design (SMPS example) and check your schematic. Are you use an L1=2.2µH between VLXSMPS and Vcap, it is Required for SMPS packages on VLXSMPS pin.

Note: It is recommended to connect the two VCAP pins together.
It is recommended to use a large plane VCAP and connect the SMPS pin to the VCAP plane with a large wire
(as the total power is flowing through this wire). Then, put the 100nF ceramic capacitor on each VCAP (as close
as possible to the VCAP ball) and add the 4.7uF on each VCAP ball.

I hope this help you!

Thank you.

Kaouthar

[Amit_En_C]

Hi KDJEM.1

Thanks for your comment, but your answer was about SMPS mode.

My problem was not about the SMPS mode. (SMPS worked fine)

My problem was related to the LDO mode. (LDO didnt wake up... there was no voltage on Vcap), and because of that issue, I had no choise but to use the SMPS mode.

Thanks,

Amit.

[STOne-32]

Dear @Amit_En_C ,

This is an expected behavior as you have an MCU reference supporting only SMPS. Which is ending by Q. To have LDO you need the part without Q at the end . This option is exclusive and not inclusive and hard coded out from our factory .

 Hope it helps you 

STOne-32

[Amit_En_C]

STOne-32 Thanks for your answer !

I see.

I think that the datasheets should be more specific, because - in your picture, it says "Dedicated pin-out supporting "SMPS".

Do I need to figure out myself that if it supports SMPS, then necessarily it doesn't support LDO configuration ?

In addition, in the datasheet they are showing how to make connections for the LDO mode.. very confusing.

Thanks a lot,

Amit.