Erroneous Tamper event

[PHXFAE]

I have a customer who is the MK21 and is utilizing the tamper detect features.  He is finding the he is getting false tamper event detections when he has a lose USB connection. The tamper detect registered is the clock., RTC he's assuming.  He's removed the check for this tamper event and right now everything is stable.  Can we get a little more information on this tamper event and why it seems like a bad USB connection could cause a false tamper event?

Thx for the help.

[PHXFAE]

The part that the customer is using is this, MK21DN512VMC5.Not sure how to figure out the mask set.

[Kan_Li]

Hi Alex,

The mask set is on the surface of the device, right below the part number, and it is related with the silicon revision, so having it would be helpful to locate the cause. Please kindly refer to the following for details.

The snapshot shot is from TWR-K21D50M, and the device on that board has the 0n89e mask set.

Have a great day,
Kan

[Kan_Li]

Hi Alex,

I just got the feedback from our AE team,and they think it is mostly caused by voltage change on VBAT. They suspected USB connection is causing VBAT change. Please kindly ask your customer to check this and let him send us the PCB layout file and schematics.

BTW, May I have more information about your customer? Thanks!

Have a great day,
Kan

[PHXFAE]

Hi Kan,

For some reason I can’t upload this on the community site so hopefully you can get it here. I do not have the mask set yet. Hopefully, I will get that soon. However, I do have his design files (attached).

Thx, Alex

[cutworth]

Hi Alex,

Could you provide your email address? I need more information to help on this.

Hao

[PHXFAE]

aschepps@arrow.com<mailto:aschepps@arrow.com>

[Kan_Li]

Hi Alex,

Thanks for the information! I have forwarded this to our Apps team, and will let you know when I have any more information!

Thanks for your patience!

Have a great day,
Kan

[PHXFAE]

Can I get someone to look at this issue.  It seems to have gone dormant.

Thx

[Kan_Li]

Sorry Alex! I was in a training last week. Would you please give me the full part number and the mask set of the MK21 that you mentioned? I will check with the IP Owner for this issue. Thanks for your patience!

Have a great day,
Kan

[karina_valencia]

Kan_Li please continue with the follow up.

[Kan_Li]

Hi Alex,

Did the issue happen when you remove MK21 from PC host? How about the PCB layout? is the clock path put closely to the USB bus? Please kindly help to clarify.

Have a great day,
Kan

[PHXFAE]

If you wiggle the USB cable, with a bad cable, it produces bad connections and thru that the tamper seems to trip. The RTC clock path is REALLY close to the chip and the same is with the OSC.