TESEO LIV3F IO Supply Voltage

[ABouk.1]

Hello,

I would like to connect a TESEO LIV3F to an STM32 MCU that is powered using a 2.4v supply.

Im wondering if I can drive TESEO's Vcc_io with a 2.4v supply or if I should use a 3.3v according to the datasheet and put a level shifter between them both.

The first option is far the best for me ...

Thanks,

[RhSilicon]

In fact, in the recommendations there is a different power range for the VCC_IO.

Manufacturers usually inform the values of VIH, VIL and VOH, VOL so that the user can confirm whether it will be possible to meet the parameters, but I did not find this, really weird. For example a datasheet of SN74HC04:

[ABouk.1]

Thanks for your reply,

Since it's the same technology than the STM32, I assume that, for the TESEO LIV3F, the minimum voltage for HIGH level is 3.3 * 0.7 = 2.31V.

The STM32 that communicates with it outputs a voltage for HIGH lvl between 1.95v and 2.4v so It may not work sometimes.

I need to figure out if it's possible to connect it directly to 2.4v and operate the I/O pins correctly.

[RhSilicon]

Really having to use only the IO bus with a higher voltage is not very interesting, but it seems to be the recommended option. What are your power supplies?

[ABouk.1]

I have 3 power supplies : 2.4v, 3.3v and 5v

I can use the 3.3v for the vcc_io but I need to use a level shifter after that.

My goal is to avoid adding this level shifter, it brings extra cost, extra power consumption ...

[RhSilicon]

Can't the STM32 be powered with 3.3V?

[ABouk.1]

Unfortunately not, otherwise the STM32L5 I'm using will use more power (i've done some measurements)

There are some devices that operates in 2.4v and communicate with the STM32L5, they would be put on the 3.3v supply too and that's even worst because the circuit is designed to operate in very low power.

If there is no way to know for sure if the TESEO LIV3F can work correctly with it's Vcc_io tied to 2.4v, I'll just go with the 3.3v and a level shifter ...

[RhSilicon]

What type of data bus are you using? UART or I2C? It might be possible to implement the shift level using discrete components.

[RhSilicon · Accepted solution]

Image sources: https://www.okdo.com/project/level-shifting/

AO3400 Gate Threshold Voltage: 1.45V and AO3401 Gate Threshold Voltage: 1.3V

[RhSilicon]

BSS138 VGS: 1.5V

https://learn.sparkfun.com/tutorials/bi-directional-logic-level-converter-hookup-guide/all