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Original question:

[FAQ] [H] Isolated Interfaces - Top Questions, Answered

ISO7821LL:Applicable for reinfored isolation with 1500V DC?

Frank Berger
Prodigy 10 points
Part Number: ISO7821LL
Other Parts Discussed in Thread: ISO7821,

Hello,

we need in our application a galvanic isolated, bidirectional communication interface which is resistant against a permanent high voltage of 1500V DC (Reinforced insulation):

In the datasheet of the ISO7821 the VIOWM is rated with 2828V but in the safe-Regulated Certifications it is only rated up to 1000Vrms for TUV (DWW package).

Is it possible to use the part for our application with 1500 DC isolation voltage?

Further requirements regarding isolation:

- Reinforced isolation

- for the application a approbation with UL 61010-1 is planned

- Creeping distance:  14,3mm

- Clearing Distance:  9,34mm 

- Temperature range: -40°..125°

Regards

Frank

  • +1
    TI__Mastermind 24025 points

    Hello Frank, 

    Thank you for reaching out. 

    Which standard is required for your application? If EN61010 is the only standard for your application, then the working voltage is 1000Vrms. However, ISO7821LL is rated for 2828Vdc as per DIN and 1450 VRMS (DWW package) by TUV (see highlighted section below) for other isolation standards. 

    Best,
    Andrew

  • +1
    TI__Genius 11205 points

    Hi Frank,

    ISO7821 is capable of withstanding 1500 DC isolation working voltage. 

    Please note that IEC 610101-1 (& UL 61010-1) standard restricts the Mains Circuit line-to-neutral (RMS or DC) voltage to 1000 V (max). For the Secondary Circuit (which is already isolated from the Mains Circuit), there is no such restriction and the working voltage can be higher than 1000 V. So depending on your application, if you are using this device in the secondary circuit (& not mains circuit) then I don't see any problem. On the other hand, if you are connecting ISO7821 to the mains circuit, then the standard will limit you to 1000 V (RMS or DC) working voltage. 

    I suggest to discuss this issue with your certification agency and it'll give you a good idea of what rating you can achieve with UL 61010-1. From ISO7821 perspective, there is no problem.

    Thanks,
    Saleem Marwat

  • 0 in reply to Saleem Marwat
    Prodigy 10 points

    Hello all,

    thanks for the quick answers.

    The Isolation barrier is not in the mains circuit (DC charger application).

    Sorry, I mismatched the part number: The right one is the ISO7821FDWWR, which has a UL and TUV number for the DWW housing.

    Details we have to clarify which the UL agency. Mayby there are Issues with DTI requirements for solid insulation at this high voltage?

    For my understanding: a permanent 1500V DC voltage is not a problem and the life time estimation for DC is similar to the  Vrms curve?

    Thanks,

    Frank 

  • +1 in reply to Frank Berger
    TI__Genius 11205 points

    Hi Frank,

    Yes, 1500 VDC is not a problem from the device perspective and for the VDC lifetime estimation, Vrms curve can be used. As a matter of fact DC lifetime is even better than RMS voltage lifetime.

    Thanks,
    Saleem