STM32L072: Meaning of ''TTa'' as IO-Structure for PA0

[Uwe Bonnes]

Posted on February 01, 2017 at 11:57

Hello,

in DocID027100 Rev 3, PA0 is marked to have an IO-Structure 'TTa' , but 'TTa' is not explained in Table 15.

Bye

[howard n2wx]

Posted on February 01, 2017 at 23:54

A different part's (STM32F302xB) datasheet legend table has TTa indicating 3.3 V tolerant I/O directly connected to an ADC

[Max]

Posted on February 02, 2017 at 07:42

Hello, 

You should probably update your datasheet.

http://www.st.com/content/ccc/resource/technical/document/datasheet/cd/46/43/83/22/d3/40/c8/DM00090510.pdf/files/DM00090510.pdf/jcr:content/translations/en.DM00090510.pdf

Rev5 explains about TTa IO type in table 12:

It also specify Absolute Maximum Ratings for this type of GPIO in table 21:

as well as General operating conditions in table 24:

 

You will also find a lot of data in the I/O port characteristics ...

[waclawek.jan]

Posted on February 02, 2017 at 08:19

Max,

Uwe made an error in the title of the thread - it's supposed to be STM32L072. The 'DocID027100 rev.3' together with google give this away... 🙂 .

I did not check other 'L0 whether this omission occurs in them too, but as Uwe said, TTa is given as PA0's type without further explanation in DocID027100 rev.3 or DS10689, whichever you like better (we don't like either 'name' but that is something you may have already guessed).

So, it's *you* (ST) who should probably update the datasheet... 😉

JW

[Khouloud GARSI]

Posted on February 02, 2017 at 10:00

Hello,

We will take care of this. The next version of the datasheet will be updated.

Bonnes.Uwe

‌, thank you very much for highlighting this.

Regards,

Khouloud.

[Khouloud GARSI]

Posted on February 02, 2017 at 11:04

Hello,

I have changed the title of the request.

The concerned datasheet is related to the STM32L072 device (and not the STM32F072).

 This will avoid the ambiguity.

Thank you all for you contribution.

Khouloud.

[Max · Accepted solution]

Posted on February 02, 2017 at 10:39

Ok, thanks for noticing.

For the STM32L0 the story is a bit different.

All the TTa type pins in the datasheets are being changed into TC types on all the series datasheet, because it's electrically equivalent for those devices. 

I guess in the case of the STM32L072 datasheet, one has been forgotten...

For STM32L0 parts, It is safe to consider any remaining TTa as TC.

And we will correct this, of course.

BR

Max

[Uwe Bonnes]

Posted on February 02, 2017 at 12:29

Hello,

sorry for nitpicking.

While in the F0 datasheet TTa stands for a 3.3 Volt tolerant input, in the L0 series 'TC Standard 3.3V I/O' stands alone and 'standard' can mean anything without further context. Probably 'Standard 3.3V I/O' stands for inputs diode clamped to VCC/VDD, but a short note confirming that view will make things clearer.

Bye

[waclawek.jan]

Posted on February 02, 2017 at 12:46

While in the F0 datasheet TTa stands for a 3.3 Volt tolerant input, in the L0 series 'TC Standard 3.3V I/O' stands alone and 'standard' can mean anything without further context. Probably 'Standard 3.3V I/O' stands for inputs diode clamped to VCC/VDD, but a short note confirming that view will make things clearer.

I'd formulate this question as 'What exactly is the difference between TTa and TC'?

According to RM0367 rev.2 Figure 22. Basic structure of an I/O port bit, analog inputs are connected permanently for non-5V-tolerant pins; and PA0 does have an analog function.

Can you please give us painfully lots of information, please.

JW

[Max]

Posted on February 03, 2017 at 03:34

On TC pins, there are clamping diodes to VSS and VDD.

On TTa pins, the upper clamping diode goes to VDDA due to the analog feature of the pin.

On STM32L0 devices, VDDA must be connected to VDD, therefore TC and TTa are electrically equivalent from a specification point of view.

Merging the two type allows to simplify the datasheet.

Everybody likes simpler specification!

On STM32F0 devices, VDD and VDDA voltage could be different therefore TTa pins require a dedicated description. like that:

for example.(from STM32F072x8 datasheet)