Different Voltage Level on IO Pins

[Panda]

Hello,

I am developing an application using STM32N657

I have datasheet DS14791 Rev 4.

There are pins for VDDIO2 to VDDIO5 and the datasheet implies that I can run the GPIO on an independent voltage supply. Chapter 5.3.17 even specifies low levels and high levels for 1.8V mode and 3.3V mode.

I need SPI and UART at 3.3V level.

I know that VDDCORE is 0.8 V, for this I will use the internal SMPS at 1.8V

Some of the voltage signals have 1V8 in their name so obviously these run at 1.8V

However I am not completely sure how I can/must supply the rest of the chip.
Can i supply VDD and VDDIOx with 3.3V and have all the GPIO work at 3.3V? What else do I have to keep in mind when using 3.3V on this chip?

Thanks

Lucas

[mƎALLEm]

Hello @Panda and welcome to the ST community,

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@Panda wrote:

Can i supply VDD and VDDIOx with 3.3V and have all the GPIO work at 3.3V?

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This is what the datasheet is saying:

So if you need all the IOs working at 3.3V you need to connect all the VDDIOx to 3.3V power supply (minimum 2.7V).

[Panda]

Hello,

thanks for the confirmation!

I guess VDD is independent from VDDIOx and supplies all GPIO that are not in the scope of VDDIOx, correct?

[mƎALLEm]

Yes VDD is independent from VDDIOx. Some IOs are power supplied from the VDD rails others from VDDIOx.

The VDD/VDDIOs distribution is described in the table 51 in the reference manual of the product::

[Panda]

Thank you for your answer and thanks for pointing me to the Reference Manual!

I understand now.

I just want to clarify one last thing and then this is answered.

I'll attach a screenshot from the RM, Figure65, GPIO Structure

Say I have VDD and VDDIOx on 3.3V, I am unsure whether I can apply a 3.3V signal to the GPIO when they are in input mode. On the screenshot it looks like the input is directly connected to the analog on-chip peripheral, which I assume runs on 1.8V.

Is there a risk of damaging the chip if I apply 3.3V in input mode?

[mƎALLEm]

That doesn't have sense if the product allows you to power supply the VDDIO at 3.3V and you cannot use the digital GPIOs at 3.3V. 

You can use the GPIOs with a power supply on VDDIO in the ranges described in the datasheet (provided above) without any issue.

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@Panda wrote:

Is there a risk of damaging the chip if I apply 3.3V in input mode?

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So the answer is: there no risk to use these GPIOs as digital inputs when the input is at 3.3V where VDDIO = 3.3V

[RomainR. · Accepted solution]

Hello @Panda 

I confirm that GPIOs (I exclude CSI Phy and USB Phy) are 3.3V Tolerant and can be independently powered at 1.8V or 3.3V.
As example, STM32N6 VFBGA264 package had VDD, VDDIO2, VDDIO3, VDDIO4 and VDDIO5 supplies.
VDD is used for GPIOA and GPIOB, some of GPIOC to GPIOH supply.
VDDIO2 is dedicated to GPIOO and GPIOP for XSPIM port1
VDDIO3 is dedicated for GPION for XSPIM port2 
VDDIO4 is dedicated for GPIOC and GPIOH for SDMMC1
VDDIO5 is dedicated for GPIOC and GPIOE for SDMMC2

You can refer to DS14791 Rev 4 Table 18. Pin description on each column "Notes", corresponds a note under the last table which indicate the VDD or VDDIOx dependency. 

I can also suggest the AN5967 - Rev 2 in section 3.1 Main power supplies.

By default, all the GPIOs are 3.3V tolerant. Refer to RM0486 Rev 2 in Table 18. OTP fuse description.
If you need to change a GPIOs group voltage level at 1.8V,

1) you need to fuse in OTP124, the corresponding bit HSLV_VDDIO5, HSLV_VDDIO4, HSLV_VDDIO3, HSLV_VDDIO2 or HSLV_VDD.
This fuse operation is irreversible.

 2) in the firmware, you also need to set the corresponding VDDIOxVRSEL in PWR_SVMCRx, refer to RM0484 Rev 2 in section 13.9.10 

For VDDIOx specifications and Absolute Maximum Recommended value, you must refer to the corresponding tables in the Datasheet as explained by @mƎALLEm 

Best regards,

Romain,

[Panda]

Thank you both for the great answers!

Best Regards

Lucas