I'm using Kinetics KI family from about 3 month. I've been realized a motor control project that works fine, adjusting an old S08 core project. It works fine, as I mentioned before, but there's a BIG problem: the samples I've been created, after some time of work (could be 1 hour or some hours) stop working! Every time it happens I find a short-circuit on MCU power supply, and I think the problem is that some transient kill my MCU. I don't know if the matter is on input pins or on Vdd rail, but I think the most probable is the second cause. I would like to know if someone can suggest me a way to save MCU from dying. Power supply is obtained from a 24V battery, a little step-down circuit (that create 12V) and than a linear 5V regulator. I've decoupled ground by connecting logic ground to power ground only at GND pin of input bulk capacitor. I've decoupled with ceramic capacitor near MCU, but i didn't insert TVS on 5V. Could be an idea? I've very little space on PCB to use and so I've limited the components but now I'm thinking that was not a good idea.
With MCU I drive (via a CMOS logic) a H-bridge driver that drives 4 power MOS. The scheme I use is the same of other applications (power supply, logic, capacitor on H-bridge, driver, ecc) in which I used S08 family MCUs, with no such problems.
I would like to hope that problem is only on power supply rail, and so with adequate filtering I can delete it.
Thank you for support.