Does STM32F730R8 has VDDA pin or VREF+ pin (LQFP64 Package)

[TA1]

Dear All,

I am designing a card using STM32F730R8 whose package is LQFP64. Datasheet makes me confused. Let me explain step by step.

1- Datasheet Page 50: There is a pinout figure and it shows that Pin 13 is VDDA.

2- Datasheet Page 57: There is a table and it explains pin definition and pin 13 is defined as VREF+ for LQFP64 package. Just below row, there is a VDDA definition and there is no pin number for LQFP64 package.

3- Datasheet Page 144: There is a note below Figure 41 and it says "VREF+ input is available on all the packages except LQFP64"

4- I also check what STM32CubeMX shows and it shows that Pin 13 is VREF+ instead of VDDA.

The score is 2 to 2.

So, what is the pin 13? VDDA or VREF+??

Someone should also correct the datasheet...

Regards,

[SofLit]

Hello,

Most probably the correct pin 13 function is VDDA and not Vref+ and Vref+ is tied internally to VDD.

I will be back to you with a confirmation.

STM32

[TA1]

Hi,

STM32CubeMX say, it is VREF+ and I trust the software :) Actually I would like to trust. I need VREF for accurate ADC conversion. I will provide external reference voltage for more accurate ADC result

My second question is that : Is it possible to supply VDDA from +3V from reference voltage generator IC, if pin 13 is for VDDA instead of VREF+. According to datasheet " VDDA must be the same potential as VDD". Is it really required?

Regards

[SofLit]

Hello,

CubeMx follows what is stated in the pinout table... If there is an issue in the pinout table , unfortunately, CubeMx will follow ;) ..

Regarding your second question and according to the note 6 under the table Table 16:

--> You need to ensure a max diff VDD vs VDDA of 300mv.

STM32

[SofLit]

I forgot to add the screenshot of the note 6

[TA1]

Hi again,

After your message and my studies, if Pin 13 is VDDA is also ok with a condition.

The microcontroller is powered from a +3.3V switch mode power supply and power supply output can be 3.35V max (@25 Celcius) (Typ 3.3V) . It can be more depending on temperature but won't be higher than 3.4V. I will use a reference voltage IC to supply VDDA and it can be 2.994V min (@25 Celcius) (Typ 3.0V). It can be lower depending on temerature but won't be lower than 2.98V.

So the different between VDD and VDDA can be 0,42V max. Do you think it cause a damage?

According to datasheet VDD can be 1.7V to 3.6V and VDDA can also be 1.7V to 3.6V if you don't see small Note 6 written in Page 92. Normally VDD and VDDA are powered in the range but VDD-VDDA (max 0.42V)) > 0.3V.

I hope it is ok.

Regards

[SofLit · Accepted solution]

Hello,

Indeed, Pin 13 is assigned to VDDA and VREF+ is internally tied to VDDA for this package. The datasheet table 10, will be updated accordingly as well as CubeMx.

As stated by the datasheet 300mv is the max diff between VDD and VDDA. So you can't exceed this difference between VDD and VDDA. 420mv exceeds this max and I think there will be an injection between digital and analog domains inside the chip. So please avoid to exceed 300mv or use another package having VREF+ pin.

STM32

[TA1]

Thank you very much... I may reduce VDD or I may increase VDDA to be in range. Actually I am usign STM32F334 in another card and VDD-VDDA can be 0.4V maximum and it is written in its datasheet. However STM32F730R8 datasheet doesn't give the specs and there is an only small note.

I cannot change the package right now. There is a big microcontroller shortage. I think you know it.. I hadn't found microcontroller for 4 months and finally I found some in stocks and I bought 2 times greater than I need to not face similar problem in near future. So I have to find a way...

Thank you very much indeed for your help. If you can add VDD-VDDA in absolute maximum range table, it would be great.