ECMF02-2AMX6 GND connection

[morzh]

Techsupport ignored my request, so I have to come here.

The part is ECMF02-2AMX6. It is CM choke plus ESD surge protector for USB2.

Here's the question: in the datasheet from June 2011 Doc ID 17815 Rev 2, this is the recommended layout is shown (see the image).

As can be seen, pins 3&4 are connected to GND (3 VIAs are being used).

However the Pin 4 is declared "NC". In the text this is not addressed. My request to the support was not answered.

THis is fairly important. If the pin i named "NC", it means "No Connect" unless the opposite openly explained in the text of the datasheet.

Waiting for an answer.

[TDK]

If it were me, I would tie it to ground and move on with the project. "NC" for dumb (i.e. passive) chips like this typically means "not connected" as opposed to "must not be connected to anything" which means you can do pretty much whatever you want with it. As a general rule, you want those tied to ground to avoid large (theoretical) potential buildups.

[morzh]

Thanks for answering.

However, having been burnt by datasheets' omissions and ambiguities in the past, I would prefer this to be clearly stated by the datasheet. I have seen some weirdest definitions of what NC could mean.
A good datasheet does not make engineer guess or assume.

[TDK]

I agree, but that is often the position you are put in as an engineer. Do your best with what is available. You are often working with imprecise information. The "NC" pin on an ESD protection chip should be the least of your worries. Ambiguity for "NC" is on things like MCUs and FPGAs and other active devices where these pins are used internally for testing, not on dumb passives.

I don't work for ST and have no power to change the datasheet. I imagine this is low on the priority list for them.

[morzh · Accepted solution]

Thanks for answering my question again.

I agree. It is low priority. But at least they could've answered the question that I asked 2 months ago and which is still hanging open.

Anywho, I will accept that.

best

Mike.