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PSoC 4 MCU

ToVa_285016
Contributor

Hi,

   

I am having an issue with a PSOC 4 product that has a terminal block for power and communication on a custom board.  When I hot swap the terminal block, it kills the microcontroller, I cannot even program it again.  When I power cycle using the power button on a power supply, it does not affect it.  The power input is 12V, which goes to a MIC2920 5V LDO, then to the controller.   There is not much more to the circuit besides a reverse voltage protection diode.

   

Any ideas?

   

Thank you,
Tom

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6 Replies
JoMe_264151
Expert II

There was an issue with the regulators when their input gets shorted and the C of the regulated side reversely discharges through the LDO killing it. Next was the killed LDO offering the PSoC the full input voltage which it deadfully accepts.

   

Another diode may protect that.

   

Bob

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ToVa_285016
Contributor

Hi,

   

Oddly enough, the LDO is not dead.  If I replace the PSOC, the new one works fine until I hot plug it again.  Just to be clear about when you say 'shorted' the VIN and GND are not shorted together, just plug in with a terminal block.  Am I understanding wrong?

   

Where would the second protection diode go?

   

Thank you for your help,
Tom

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JoMe_264151
Expert II

The case I am talking about was solved by placing the diode allowing flux from LDO output to LDO input.

   

And, yes, it was a short between Vin and GND shortly after Vin power disconnected.

   

 

   

Bob

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ToVa_285016
Contributor

Hi,

   

Would this have any bearing seeing that it is not the LDO that is dying, but the chip itself?  When the chip dies, GND and 5V are shorted together in the chip  itself, when I remove the chip, they are open again.

   

Regards,

   

Tom

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JoMe_264151
Expert II

Difficult to understand what you are saying: Do you tell that the damaged chip (power shorted) gets repaired when you remove it from your board??? Check all other parts (caps, Ds)

   

 

   

Bob

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ToVa_285016
Contributor

Hi,

   

Sorry for the confusion.  When I hot swap the power connector, the PSOC itself is damaged, and cannot be repaired.  The rest of the circuit does not seem damaged because if I solder a new PSOC in, it works as before.

   

Thank you,
Tom

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