ISOW1412: Low EMI layout question

Hi Youhei,

Please find my inputs below:

Youhei Miyaoka said:

1. How wide does they need to secure for KOZ?

A minimum of 2mm distance between any metal and KOZ is recommended for the effectiveness of KOZ.

Youhei Miyaoka said:

2. In the case of a multi-layer board, should all layer's KOZ not wire all signal lines and GND solid (except RS485 signal lines)?

Yes, KOZ should be maintained through all the layers.

Youhei Miyaoka said:

3. For low EMI design, should customer tie 1pin-20pin with coupling capacitor or 10pin-11pin with coupling capacitor or both is recommended?

I believe that you are asking about the stitching capacitor across the ground planes.
Since the primary source of emissions is the Isolated DC-DC converter, whose grounds are GND1(Pin10) and GND2(Pin11), placing the stitching capacitor near to Pin10 & 11 is most effective. However, adding one additional capacitor near to Pin1 & 20 will further assist in reducing overall EMI performance.

Youhei Miyaoka said:

4. ISOW1432 and ISO1412 have same EMI result under the same conditions?

Yes, since the internal power converter which is the primary source of emissions is exactly same in both the devices, the emissions are will be same for ISOW1412 and ISOW1432.

Regards
Varun