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Adum2250 immunity issue

Hello,

I am facing problems with Adum2250 I²C isolator

I my application, we have electromechanical relays that make Adum2250 internal detector to trig when the relay commutes

I have attached the waveforms : 

(BLUE) = Clock side 1 (5V)

(PINK) = Clock Side 2 (3,3V)

(YELLOW) = Relay output (230Vac - 50Hz)

The distance between the relay and the chip is around 3cm

Question : what would you suggest to fix the problem ?

attachments.zip
  • Hello Travis,

    The ADuM2250 is based on the oldest iCoupler encoding scheme.  It is more sensitive to disterbences on the power supply than the newer iCouplers.  So I would approach this by filtering the power supply on both sides.  Increase the size of the bypass cap between VDD and GND.  and I would add ferrites or even regular resistors outside of the bypass.  You can add a fairly large resistor, 100-200 ohms without dropping the voltage significantly.  If that does not work, then try putting a safety cap between GND1 and GND2 to slow down the transient between the grounds when the relay engages, sometimes that violates the max dV/dt with fast switching events like a mechanical relay. 

    Let me know how it works out.

    Best Regards,

    MSCantrell

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