GPIO ESD protection

Technical Support
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1

Hi,

We connected a rotatory encoder to GPIO5 and GPIO3 of our imx8qm and we unfortunately broke GPIO5 due to an ESD. The good news is that everything else seems to works fine.

Looking at your schematics of Ixora V1.1B and V1.2A it seems that all GPIO are connected to X1P without any ESD protection, so i would like to ask you what could we do to protect these GPIO.

Do we have to protect them on our side by connecting an ESD protection between the encoder and x27?

Thanks

Enrico

2

Hello Enrico,

Well, there are many ESD protection devices available like TVS diodes.
But first, make sure that it was really an ESD. And check the output of the Encoder and the voltage just to be sure that there is not something wrong.
Well, The GPIO of our module is not protected per default for higher ESds then the Internal ESD protection of the IMX8 SoC. The IMX8 ESD tolerance is defined in the IMX8QM SOC datasheet as ESD(HBM) 1KV and ESD(CDM) 250V. Since there are many different functions possible with the GPIO pins a ESD protection diode might limit the use for the customer (speed).

Best Regards,
Matthias

3

Hello @matthias.tx,

Thank you very much. These values are a little bit low, so we will go for an external ESD protection.
The encoder will be connected to a knob that user can manually rotate.
What ESD protection device do you suggest for this specific use case?

Thanks

Enrico

4

Hello Enrico,

you could use the same protection device like the TPD2EUSB30DRTR that we are using to protect the USB interface in our carrier board ref. schematic.
Best Regards,

Matthias

5

Hello @matthias.tx,

Is it possible to connect these devices directly to the ixora carrier board or will we have to connect them externally (maybe on an external board that connects the encoder to the ixora)?

6

Hello Enrico,

So if you are not designing your own carrier board based on our ref. design but you are using our carrier board you could also integrate the protection on our custom User interface board. But you must be able to exclude that an ESD can strike the GPIO pin behind the protection device.

Best Matthias