How to filter differential-mode interference from power FTUs?

Differential-mode interference mainly manifests as noise between power lines, affecting the sampling accuracy of the FTU. The solution employs a π-type filter structure. A PWRA6045R6R8M0T power inductor (6.8μH) is connected in series at the DC power input, along with two 47μF/100V electrolytic capacitors and a 100nF/100V C0G ceramic capacitor in parallel. For the AC sampling circuit, a PBZ3216E120Z0T ferrite bead (120Ω@100MHz) is connected in series, along with two 10nF/630V safety capacitors for differential-mode filtering. In the PCB design, the power traces are widened to 2mm to reduce parasitic inductance, and the filter capacitors are placed as close as possible to the IC power pins, with a distance of less than 5mm. Simultaneously, an ESD3V3D3B protection is used to protect the sampling ADC input. This solution can reduce differential-mode noise by more than 35dB and power ripple by less than 50mV, meeting the IEC 61000-4-17 voltage fluctuation test requirements.