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ISO7521C / reinforced isolation , IEC 60950-1

Ryuji
Guru 20090 points
Other Parts Discussed in Thread: ISO7521C

Hello,

I have questins about ISO7521C reinforced isolation.

(1)
ISO7521C is certified IEC60950-1.
Could you please let me know what parameter in the ISO7521C datasheet could satisfy the IEC60950-1?

(2)
Please let me know ISO7521C structure for achieving the reinforced insulation.

Our customer requests these information for explaining to their end user.

Best Regards,
Ryuji Asaka

  • 0
    TI__Genius 10005 points

    Hello,

    Please review the CSA and TUV certificates for ISO7521C at the following webpage for details of reinforced rating:

    http://www.ti.com/product/ISO7521C/technicaldocuments

    Please let me know if there are additional questions.

  • 0 in reply to Saleem Marwat
    Guru 20090 points

    Hello Saleem san,

    Could you please kindly let me know about the following description in the datasheet and certifitetion?

    --------------------
    5000 VRMS Reinforced Insulation, 400VRMS maximum working voltage
    5000 VRMS Basic Insulation, 600 VRMS maximum working voltage
    --------------------

    Could you please let me know the difference of 400Vrrms and 600Vrms?
    Is testing method difference ?

    Best Regards,
    Ryuji Asaka

  • 0 in reply to Ryuji
    TI__Genius 10005 points

    Asaka-san,

    The following isolation ratings are provided by TUV per EN/UL/CSA 60950-1.

    --------------------
    5000 VRMS Reinforced Insulation, 400VRMS maximum working voltage
    5000 VRMS Basic Insulation, 600 VRMS maximum working voltage
    --------------------

    Reinforced insulation requirements according to this and most other standards are tougher, therefore ISO7521C has a lower working voltage for reinforced insulation applications and higher working voltage for Basic insulation applications.

     

  • 0 in reply to Saleem Marwat
    Guru 20090 points
    Hello Saleem san,

    Thank you for the reply.
    Please let me know about the following.
     
    (1) distance through insulation
    According to 60950-1 , I think that Reinforced insulation need 0.4mm of  distance through insulation.
    However ISO7521C distance through insulation is 0.014mm only.
    Could you please let me know this reason ?
     
    (2) Maximum Working VOltage Test Method
     Could you please let me know test method of maximum working voltage ?
    I would like to know it about Reinforced insulation and Basic insulation each.
     
    Best Regards,
    Ryuji Asaka
     
     
  • 0 in reply to Ryuji
    Guru 20090 points
    Hello Saleem san,

    Sorry for bothering you but could I have the replay please ?

    Best Regards,
    Ryuji Asaka
  • 0 in reply to Ryuji
    TI__Genius 10005 points

    Hi Ryuji,

    I apologize for the delay; we had a long weekend in the US.

    Following are answers to your 2 questions:

    (1) distance through insulation

    Even though many standards have 0.4mm distance through insulation requirements, the same standards also have other provisions which allow thinner insulation layers to be accepted under certain conditions. For example, see the attached excerpts from IEC 60950-1.

    4174.IEC 60950-1 DTI Requirements.docx

    That is why we receive Reinforced Isolation ratings from safety agencies.

    (2) Maximum Working VOltage Test Method
     
    Texas Instruments uses TDDB (Time Dependent Dielectric Breakdown) method to determine the intrinsic working voltage capability of our devices. Certification agencies use criteria based on the requirements of the specific standard. It includes, but not limited to, Creepage and Clearance, Pollution Degree, Comparative Tracking Index, other IEC standard specific requirements, etc.
     
    I hope this helps.

      

  • 0 in reply to Saleem Marwat
    Guru 20090 points
    Hello Saleem san,

    Thank you for the reply.
    Concerning (2), are there any test method difference between woking voltage of standard insulation and  woking voltage of reinforced insulation?

    Best Regards,
    Ryuji Asaka
  • 0 in reply to Ryuji
    TI__Genius 10005 points

    Asaka-san,

    Through TDDB analysis, Texas Instruments determines intrinsic working voltage of a device or a technology node, so basic or reinforced working voltage has no test difference.

    As far as certification agencies are concerned, the requirements for basic or reinforced insulation are dependent on specific IEC standard that is being used, for example, IEC 61010-1, IEC 60950-1, IEC 60601-1, etc.  In general, for a specific device, reinforced working voltage is typically half the value of basic working voltage. In other words, requirements for reinforced are twice as stringent as basic working voltage.

    I hope this clarifies the situation.