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STM32N6 Internal SMPS Reference Design

kevlar
Associate

I've been trying to find examples of the STM32N6 using the internal SMPS however, other than trying to reverse engineer the Nucleo or Discovery boards, there doesn't seem to be much literature available showing this.

Ideally (for cost and board layout reasons), I just want to power the N6 with a single 3.3V supply (plus the 1.8V AON supply) and use the internal SMPS to provide VDDCORE.

Can anyone point me in the right direction, please?

 

15 REPLIES 15
LCE
Principal II

1.5A ? Really ?
Or do they mean maximum current spikes / peaks which could be handled by big / enough capacitors?

This was based on the maximum current on IDDCORE shown in the reference manual with internal SMPS and Tj max of 125 degrees Celcius and all peripherals enabled (1100.0mA). Better to be safe than sorry? Plus, I have other things I want to supply with 1.8V too...

EDIT - the Discovery board has 3A regulators on there for 3.3V and 1.8V...

@kevlar 

For all current consumption you need to refer to DS14791 Rev 3 all the table related to SMPS internal.

5.3.6 Supply current characteristics in Run Mode

IDD (VDD) is Table 32. 

IDDCORE (VDDCore) is Table 34 (there is a Typo error under fix for Symbol IDDA1V8)

IDDA1V8 (VDDA1V8) is Table 36

IDDA18AON (VDDA18AON) is Table 38

IDDSMPS (VDDSMPS) is Table 39.

In internal SMPS, IDDSMPS therefore depends on the IDDCore including the internal SMPS efficiency, the voltage ratio (VDDSMPS/VDDCore), and the different external losses (leakage or dissipation). If you need to size the external regulator of the VDDSMPS, you should consider IDDSMPS which corresponds to the VDDCore condition of table 34.

VDDIO4 and VDDIO5 are 3.3V as default. But can be powered at 1.8V by changing OTP124 HSLV_VDDIO4 and HSLV_VDDIO5 when they are configured in SDMMCx
VDDIO2 and VDDIO3 are 3.3V as default. But can be powered at 1.8V by changing OTP124 HSLV_VDDIO2 and HSLV_VDDIO3 when they are configured in XSPI1 and XSPI2 for external memories or other devices which require 1.8V.
Note: In complement of corresponding OTP124 HSLV_VDDIOx bit to set for 1.8V configuration, there are also some register PWR_SVMCRx to configure when GPIOs in VDDIOx domain need to operate at 1.8V

Best regards,

Romain,

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kevlar
Associate

Thanks for the comments on this thread. I have enough information now to progress. Cheers!

LCE
Principal II

Better to be safe than sorry?

Absolutely!

I usually make any voltage supplies for double the maximum current that I expect.

But 1.5A seemed a lot to me, but okay new fast machine...


@LCE wrote:

But 1.5A seemed a lot to me, but okay new fast machine...


And here was me thinking 1.5A wasn't enough! Should be fine for my use case... hopefully