iCoupler ADuM524x CTI-value


I use an iCoupler ADuM5242 in a device that is currently under test at UL.

Regarding the safety clearances, the UL inspector does not accept the CTI value of 175V described in the document. He says it was not tested under UL and so, he cannot accept the described value issued by the document.

The application has got on the lower side a circuitry that is connected to SELV. The iso side is connected to 250V at the most.

Is there any argument I can express that the ADuM5242 is suitable nevertheless?

Thanks for your help.

Regards, Andreas

  • 0
    •  Analog Employees 
    on Oct 30, 2018 9:16 PM


    I have asked our expert on isolation and certification about this and here is his response:

    Yes, this part should meet the requirements for single protection.  According to IEC60664-1, the insulation coordination standard, SELV is <60V so we are looking at a total of 310V max for the cross barrier and even under Material Group III that only requires 3.2mm of creepage.  The impulse requirement is 2500V peak for Over Voltage Category II.  These parts are rated for 2500Vrms transient withstand which covers peak voltages of 3500V.  I think these will be adequate.  


    There are newer parts than the ADuM524x, with better efficiency and lower power requirements, I would recommend the ADuM5210 even though the board space is a little larger.

    Regards, Brian

  • Hi Brian,

    thank you for your prompt answer.

    UL requires at this spot reinforced protection and the needed space will be @250V 2.5mm x2=5mm according the regulations 61010.

    Is the CTI ranking not tested by UL?

    Regards, Andreas

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