LPC4357 debugging pins damage

[lpcware]

Content originally posted in LPCWare by Ramana on Wed Nov 04 01:23:04 MST 2015
Dear all,
I'm using LPC-Link2 debugger for my Own PCB with LPC4357.
Some times debuggers pins are getting damaged. It is working only after controller is replaced with new one.
I haven't faced the similar problem with remaining series of MCUs(LPC1778/69 etc.,).

I thought it was due to high current sink/source into/from JTAG the pins.

Is it possible to rectify the issue using series resistors?

Thank you in advance.

[danlhajek]

I can confirm this strange behavior. Sometimes JTAG pins are damaged and there are strange voltages on them. I personaly fried at least 5 chips this way and only solution si replace IC. In some cases chip works fine, but is not posible to debug, sometimes stops working completly, one time was roasted to death (current more then 1.5A at 3.3V rail even in forced reset state). I have traced probable origin to some spikes when you connect/disconnect LPCLink (2.0 or older). Only working "solution" was to connect computer case to GND of debuged board. From this time there was no problem with this kind of damage. JTAG pins are somewhat sensitive on something.

Edit:

As mentioned here (Solved) LPC-Link 2 Apparently burning out JTAG connections   I have added 2k2 resistors to JTAG data lines too. Woks fine on ~10cm long cable and can not make situation worse.

[lpcware]

Content originally posted in LPCWare by Ramana on Thu Nov 05 20:50:30 MST 2015
I've tried for it, but those are dedicate JTAG pins. I've tried to connect through SWD, But the same problem was repeated.

[lpcware]

Content originally posted in LPCWare by mysepp on Thu Nov 05 00:22:04 MST 2015
Have you tried (or can you try) if the damage of the pin affects only the JTAG functionality?
Is it working when you switch them to GPIO and let them toggle?

[lpcware]

Content originally posted in LPCWare by Ramana on Wed Nov 04 21:48:31 MST 2015
Thank you,
I have already gone through that link.
I've tried in ISP mode too. I concluded the damage of pins only after verification of pins' voltage using multi-meter.
Voltage was neither 'logic high' nor 'low', it was about 1.8 to 2Volts. For the working cards same pin levels are fine.

When the JTAG pins are damaged, controller was working fine(programming in ISP and code running were OK)

[lpcware]

Content originally posted in LPCWare by vtw.433e on Wed Nov 04 07:14:49 MST 2015
What makes you think the jtag pins are damaged? Could it just be that you need to boot into ISP mode as described here?
https://www.lpcware.com/content/faq/lpcxpresso/regaining-debug-access

[lpcware]

Content originally posted in LPCWare by Ramana on Wed Nov 04 05:32:34 MST 2015
No, direct TTLs are terminated without any protection.
I haven't seen any protection circuit for JTAG in any one of the boards.

[lpcware]

Content originally posted in LPCWare by Martin84 on Wed Nov 04 05:23:32 MST 2015
Do you have TVS-Diodes against ESD near the JTAG Connector?