USBLC6-2SC6 ESD wont protect

[Laszlo Nagy Kanasz]

Posted on August 24, 2017 at 09:47

Hi

We have a device which is an USB powered(USB2.0), and on the same USB port is the communication with the PC.

So it is powered from the PC.

For the ESD protection of the USB lines we add the USBLC6-2SC.

Our processor is a TIVA TM4C1294NCPDT type.

The device is continually streaming, the PC program only captures what the device is sending.

The problem is with the ESD events.

We tray in laboratory, and a 2kV ESD spike is enough to make problems.

As we see the device wont stops, nor even reset, so the ESD spike is not interrupting the streaming, but the PC detect a disconnect of the USB device, and after it connects back automatically...(but we have to restart our capturing program

every time)

Is this a specific problem related to our HW design, or the problem is with the ESD protection chip itself.. I read on some posts that this ESD TVS array is not the best for the cases when the VBUS status is detected... but our case is not that.. we does not pull off/on the USB plug, and the power line (VBUS) is working continually (we use some galvanic separation DC/DC to power our processor part from the VBUs line).

Is there some issues using this ESD protection ?

Should we use some other type, other methods?

Part of our USB power/communication schematics section is attached.

Best Regards

Laszlo

[AvaTar]

Posted on August 24, 2017 at 15:06

I understand the selection of the proper forum (or fora) is a bit difficult with a mixed design.

So my question here is: Is it a normal situation with the USB?

I would guess so. With the relatively high energy levels of burst/surge tests, a signal corruption is more than probable, especially with the high USB signal frequencies.

Could any of the safety solutions give a safety level in which does not comes to this communication error?

Not that I'm an expert, but I think not.

Safety levels are concerned with the entire system, which needs to detect unsafe/dangerous states and assume a safe state and avoid possible damage to health/live.

I don't know of any requirement to automatically recover from such events.

But don't take my word for it ...

[waclawek.jan]

Posted on August 24, 2017 at 15:07

So my question here is: Is it a normal situation with the USB?

The short answer is that yes.

Could any of the safety solutions give a safety level in which does not comes to this communication error?

The short answer is that no.

and the whole story is only about to prevent burning out the device elements, and not to enable a continuous communication.

That's the short version of the story.

JW