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ISOUSB211: Creepage of the land pattern is 7.3mm so not meeting 2MOPP (requiring >8mm) at the board level?

Part Number: ISOUSB211

Dear Support Team,

I have a question on whether we can achieve a Creepage > 8mm for the board on which ISOUSB211 is mounted (NOT ISOUSB211 itself).

1. According to the ISOUSB211 datasheet (Rev.C, page 7), the Creepage is >8mm. 

2. However, according to the same datasheet page 41 (also in the Gerber file of ISOUSB211DPEVM, TOP layer), the shortest distance between the copper land pattern of side-1 and side-2 is only 7.3mm (9.3 - 1 - 1 = 7.3), which is less than 8mm.

3. There should be an "Air Gap" between the bottom side (black resin) of the ISOUSB211 chip and the mounted board surface. The datasheet indicates the "Air Gap" height to be between 0.1mm and 0.3mm (see page 40, lower-right).

4. There should be a risk that the Creepage distance equals 7.3mm if using your recommended land pattern, since there exists such an "Air Gap" creeping discharge path between the land patterns of side-1 and side-2 through the surface of the mounted board.

I understand that the Creepage distance of the ISOSUB211 chip itself is >8mm, there is no doubt here.

But when I mount it on a board, how can I achieve the Creepage > 8mm at the board level?

(With high possibility, I have a misunderstanding about Creepage defined in many IEC 60***-1 standards, but I can not find a suitable description.)

Thank you in advance.

  • Hi Xueliang,

    Thank you for reaching out and for showing interest in ISOUSB211.

    I am not sure if you have noticed the two land patterns provided on page 41 of ISOUSB211, the land pattern on the left provides a creepage of 7.3mm while the one on the right provides a creepage of 8.1mm. I am copying below a snapshot of these land patterns from ISOUSB211 datasheet page 41.

    Please also note that, based on the tolerances that a PCB manufacturer supports, you may have to adjust the footprint according to your needs to meet your creepage requirements. Please let me know if you have any further questions, thanks.

    Koteshwar Rao

  • isousb211.pdf

    Hi Koteshwa

    Thank you for your prompt and clear answer. This issue is now resolved.

    I found it a bit curious that the Rev. C datasheet I downloaded earlier (attached here) only had the left picture. However, when I downloaded it again today, I discovered two pictures on page 41.

    Thank you anyway  :)