MaxLinear XR79115 | Demoboard ANP-47

Description

A well laid out PCB does not radiate much EMI all by itself from the current carrying traces. In order to get EMI compliancea PCB should have:■■ Ideally six layer PCB with two full ground planes. Four layer PCBs are okay.■■Make sure there is sufficient vias between the ground planes.■■Make sure to minimize the switching current loops on the board.■■Current carrying traces must be kept as short as possible and running on a layer close to the ground plane.■■ Power ground plane and the signal ground must be connected at only one point.Most of the radiation takes place when we connect leads to the power source and the electronic load. These leads areusually about 0.5m to 1.5m and they act as a very good antenna for frequencies between 30MHz to 1GHz.Figure 1 depicts a typical test setup in anechoic EMI test chamber. The high frequency power switching generates widespectrum noise because of all the parasitic inductances and capacitances ringing at different frequencies and with differentdamping factor at different times of the switching period.

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