AnsweredAssumed Answered

Short circuit between Vdd and Vss

Question asked by Giovinetti Roberto on Apr 24, 2014
Latest reply on Dec 6, 2016 by wei sun

Hello everybody

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.

Roberto

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