Core supply for STM32H573MIY3Q

[MarwinS]

Hello,

we have to use the STM32H573 in the 80 Pin WLCSP with temperature Range 3 (to 125°C). So STM32H573MIY3Q was chosen. Due to a mistake we didn't recognized that the internal LDO can't be used. Now we have no space for placing additional components as the inductor to use the SMPS. The STM is on a tiny board which is connected on a baseboard on this is more space for components.

So now we have two options:

1.  Use an external LDO on the tiny board, we have 1,8V spare to burn down. How much current shall we consider (250 MHz). The maximum IDD ist stated with 125,2 mA, does any additional current has to be added?
2. Use an external DCDC on the baseboard.

 

In both cases the Questions are:

How has the pins of SMPS to be configured (by hardware) to shut down the SMPS appropriately?
Do we have to use the VCAP as an input?

If STM staff is reading this please get in touch with us immediately. Thanks.

So long
Marwin

Edits: Some minor spellings

 

[TDK]

> Due to a mistake we didn't recognized that the internal LDO can't be used.

??  You're not required to use SMPS.

 

See "Figure 6. STM32H523/H533/H562/H563/H573 power-supply scheme with LDO" in the following document:

Getting started with STM32H5 MCU hardware development - Application note

 

 

> The maximum IDD ist stated with 125,2 mA, does any additional current has to be added?

Is there other stuff on the board that will be taking current? Do you want any margin? If not, just plan for 125 mA.

 

[abba]

> ??  You're not required to use SMPS.

Yes you are (assuming you don’t have an external 1.2V supply - an option the OP has already noted). See:

stm32 - STM32H573 LDO has no output - Electrical Engineering Stack Exchange

TLDR: The LDO is not enabled on the SMPS packages, and we all should have known about this because there’s a footnote on an STM marketing webpage somewhere that mentions it.

[abba]

I also could not resist the appeal of the tiny package & rich peripheral set with this part, and was also initially confused by the lack of LDO. (A fact I discovered when prototyping with another SMPS package of STM32H573 and finding LDO not working).

Unfortunately your bigger issue with this part is availability, unless you were smart enough to buy your parts in volume before starting the design (do you have any extra for me?)

[AScha.3]

So…

A: If you don't want to use the SMPS then select the non-SMPS package that has LDO enabled. Which means a redesign.

B: Include the inductor and connections to use the internal smps.Which means a redesign.

C: add a external Vcore supply . Which means a redesign.

your decision…

+

availability : 

 

[abba]

Re:
 

> A: If you don't want to use the SMPS then select the non-SMPS package that has LDO enabled. Which means a redesign.

Not just redesign, but 20x more board space. No other package variant comes close to the WLCSP in footprint size. And WLCSP is only available in SMPS. (For me, if I had that much board space, my solution would be completely different - I would change all of the chips, including the microcontroller, and a much cheaper microcontroller would work.)

Re: availability: right, if you don’t need WLCSP, then availability is not an issue. The problem for OP (and me) is that we DO need the WLCSP, but it’s not available.

[AScha.3]

Ok, i see - STM32H573MIY3Q - no stock now.

[abba]

Re: inductor space:

Can you squeeze a tight 0603 pad somewhere? I don’t think the inductor needs to be near the microcontroller. I am using 535-AOTA-B160808S2R2MTCT-ND / C22416563 (lsat=1A, 0603).

Another thought: if you can reduce the clock frequency (and core voltage accordingly) or aren’t using the most power-hungry peripherals, you might be able to get away with a smaller inductor, e.g.,587-LSCND1006HKT2R2MFCT-ND (lsat=0.8A, 0402).

Have you already shrunken all of your VDD/GND and VCORE/GND caps to 0201 or 01005? (If not, you should be able to make room for a new 0402 component)