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PSoC 4 MCU

NaMo_1534561
Contributor II

Hello,

What happens if overvoltage is given to the Vdd of PSoC?

Generally, I think there is a short circuit between VDD and GND, but customers are asking me to investigate whether the overvoltage applied to Vdd can appear on the output port and damage the peripheral circuitry.


MPN CY8C4025AXI-S412

Best Regards,

Naoaki Morimoto

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1 Solution
Len_CONSULTRON
Honored Contributor II

Naoaki-san,

I'm afraid you misunderstood my description.

The overvoltage condition I mentioned is on the IO pin with respect to VDD or VSS.

Therefore the protection diode could be damaged as I described in the "IO-VDD and IO-Vss" case.

If you are talking about Overvoltage on the VDD of the IC you would see more significant failures.  Possibly VDD-VSS shorts on one or more pins along with other internal failures.  In this case,  either the CPU would stop working or if working it would draw excessive current in active or sleep modes.

Len
"Engineering is an Art. The Art of Compromise."

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3 Replies
Len_CONSULTRON
Honored Contributor II

Naoaki-san,

It is possible to damage the PSoC4 with a voltage on a pin (input or output) at VDD+0.5V or VSS (GND) -0.5V.   If this occurred it would have to be either a high energy voltage transient with >100mA current for a short time OR a low-energy transient for a long time.

Here is how I usually tell if an input or output is damaged:

  • Start with the PSoC powered off.
  • Set a DMM to diode detect mode.
  • With the DMM '+' probe on the IO pin and the '-' on VDD, do you measure about 0.5 to 0.6V?  
    • If yes, the IO is probably not damaged with an overvoltage condition.
    • If no and you read a low resistance (< 5 ohms) you probably have overvoltage damage.
    • If no and you read a very high resistance (>100K ohms) you probably have overvoltage damage.
  • With the DMM '-' probe on the IO pin and the '+' on VSS (GND), do you measure about 0.5 to 0.6V?  
    • If yes, the IO is probably not damaged with an undervoltage condition.
    • If no and you read a low resistance (< 5 ohms) you probably have undervoltage damage.
    • If no and you read a very high resistance (>100K ohms) you probably have undervoltage damage.

When overvoltage/undervoltage damage occurs this is usually because the ESD protect diodes have fused the PN junction due to too much energy (current x time) when biased in the diode forward direction.  This fusing will appears as short between the IO pin and VDD or VSS.  This is the reason for the low resistance in the diode forward direction. 

If the energy is high enough and/or long enough the short will literally blow the diode (and other internal circuits) and you will see a very high resistance because the diode has evaporated in a high energy event.  This can be also seen if you were to 'decap' the IC and look at the IO pin on the die.  It will look like a tiny 'crater'.

If you are creating automotive designs, as I have, the testing is rigorous and there are some very nasty electrical pulses.   One particularly nasty one is the ISO Pulse 5 or Pulse 5b.   I have been 'bitten' more than once with an insufficiently protected circuit.  Another series of nasty pulses are the ESD series.

Len
"Engineering is an Art. The Art of Compromise."
NaMo_1534561
Contributor II

Hello Len-san,

Thank you for your answer.
The protection diode of the I/O port is damaged by the overvoltage to Vdd, and depending on the situation at that time, either open failure (resistance value becomes extremely high) or short failure (resistance value becomes extremely low) is entered. I understand that there is a possibility.

In most cases, the diode on the VDD side will be damaged and a short circuit to VDD-Vss will be observed.
But as you answered, it is possible to consider short cases of IO-VDD and IO-Vss, right?

Best Regards,

Naoaki Morimoto

 

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Len_CONSULTRON
Honored Contributor II

Naoaki-san,

I'm afraid you misunderstood my description.

The overvoltage condition I mentioned is on the IO pin with respect to VDD or VSS.

Therefore the protection diode could be damaged as I described in the "IO-VDD and IO-Vss" case.

If you are talking about Overvoltage on the VDD of the IC you would see more significant failures.  Possibly VDD-VSS shorts on one or more pins along with other internal failures.  In this case,  either the CPU would stop working or if working it would draw excessive current in active or sleep modes.

Len
"Engineering is an Art. The Art of Compromise."

View solution in original post

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