Need STM32 GPIO operate on 1.8v

[bluenow1896]

Posted on August 03, 2017 at 20:26

Hi, recently in a project I need the GPIOs on STM32 to operate on 1.8v logic level. By quickly looking through datasheets, it seems many of STM32 can do so, for example, to STM32F407VG, if provide 1.8v to VDD, it runs GPIO on 1.8v level. However, I have difficulty to make such changes on TM32F4Discovery board, as there is no 1.8v power source available on the board.

Now I have the question, which ST Discovery board or Nucleo board can support &sharp1.8v GPIO easily? I want to try it out. I need the board support USB port as USB device, and run the GPIO on 1.8v, it would be better if it provides I2C slave interface on 1.8v also.

Thanks for your advice.

-Andy

#1.8v-gpio

[Tesla DeLorean]

Posted on August 03, 2017 at 21:04

USB won't work from a 1.8V supply. You'd need an L series part with a VDDUSB pin to power the transceiver.

When interfacing to 1.8V modules with the F2/F4 we use level translators, some TI part with 8 bidirectional channels as I recall.

[S.Ma]

Posted on August 03, 2017 at 22:12

Start from looking at the STM32L4 family. It has separated USB, VDDIO1 and VDDIO2 supplies which would enable a rich mix of diverse supply voltages to coexist. For each group of GPIO supply voltage there are the usual serial interfaces suspects. This way, external voltage shifters might be avoided.

[bluenow1896]

Posted on August 03, 2017 at 21:46

Thanks for reply. I'm not sure what do you mean 'USB won't work from a 1.8V supply'?  Do you mean that when provide VDD 1.8v to STM32F407VG, the USB interface on STM32F407VG wasn't work?

If I have to use a STM32L4xx , that is fine, let me know which Discovery board or Nucleo board be best for me for this prototype?  As I mentioned early, I need an USB device interface, 1.8v GPIO , and 1.8v I2C slave interface on the evaluation platform.

I will like to avoid to use extra circuit to do the level shift.

Thanks again.

-Andy

[Szymon PANECKI]

Posted on August 03, 2017 at 22:22

Hello Andy,

Looking at the requirement:

I need the board support USB port as USB device, and run the GPIO on 1.8v

it seems to me that maybe STM32L4 can be an interesting solution for you. STM32L4 in packages with big amount of pins (LQFP144, BGA132, CSP72 and CSP81) have VDDIO2 domain. This domain has a dedicated supply pin, which level can be in range of 1.08 ? 3.6V, comparing to VDD 1.71 ? 3.6V and VDDUSB 3 - 3.6V. VDDIO2 domain supplies only pins from GPOIOG, while VDD supplies rest of the GPIOs. With this solution you can easily get a voltage level tranlator or pins operating on different voltage levels.

Regarding the evaluation boards with STM32L4: you can use

http://www.st.com/content/st_com/en/products/evaluation-tools/product-evaluation-tools/mcu-eval-tools/stm32-mcu-eval-tools/stm32-mcu-nucleo/nucleo-l496zg.html

, as it offers STM32L496 in LQFP144 package. Unfortuantely VDDIO2 on this board is connected to VDD, so you would need to cut a wire and make hardawre modification on your own.

Regards

Szymon

[Jismal Jamal]

Posted on May 14, 2018 at 14:25

Hello Szymon

Panecki.Szymon.002

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I am in similar situation With STM32L496VGY. I am trying to operate VDDUSB @ 2.7V (I can increase upto 3V). But All other VDD (Including VBAT,VDDA,VREF+) @ 1.8V. From the datasheet I found a statement saying that ''The USB OTG full speed transceiver functionality is ensured down to 2.7 V but not the full USB full speed electrical characteristics which are degraded in the 2.7-to-3.0 V VDD voltage range''. Which VDD datasheet is referring to is it VDDUSB or all other VDD(Including VBAT,VDDA,VREF+). If that the case do i need increase the VDD(Including VBAT,VDDA,VREF+) to 2.7V to make USB working.

http://www.st.com/content/ccc/resource/technical/document/datasheet/group3/3f/73/19/d1/d4/9e/48/34/DM00284211/files/DM00284pdf/jcr:content/translations/en.DM00284pdf

Voltage Distribution Schematic

Table from datasheet

[Tesla DeLorean]

Posted on May 14, 2018 at 15:50

PA11/PA12 don't meet USB electrical specs below a 3.0V supply. I'd assume the ramification there would you couldn't get USB certification, and attachment would be problematic across the installed user base. I generally prefer that the tech support staff don't want to murder me or poison my coffee.

[Jismal Jamal]

Posted on May 14, 2018 at 16:04

Hai Clive

Its seems there is less clarification on mixing up different voltage on STM32MCU. Anyway I am willing to accept USB function with degraded performance.

[Szymon PANECKI · Accepted solution]

Posted on May 16, 2018 at 11:27

Hello Jismal Jamal,

Thank you for designing with STM32L4 MCU. If you want to use USB, then you need to keep VDDUSB on at least 2.7V, while rest of VDD pins can be supplied with lower voltage, for example 1.8V, which you mentioned.

Statement, which confirms this can be found is ST documentation: application not

http://www.st.com/content/ccc/resource/technical/document/application_note/group0/0b/10/63/76/87/7a/47/4b/DM00296349/files/DM00296349.pdf/jcr:content/translations/en.DM00296349.pdf

. Please see the extract below:

Regards

Szymon

[Jismal Jamal]

Thank You Szymon. The project was a succesfull one, USB work as intended.