Abstract

This document demonstrates how printed circuit board (PCB) input trace or cable design affects radiated emissions electromagnetic interference (EMI) performance for Texas Instruments’ AMC3301 precision isolated amplifier with integrated DC/DC converter. The AMC3301 family as shown in Table 6-1 does not produce excessive radiated emissions by themselves and are capable of passing CISPR 11 class B without additional components as shown in Figure 2-2 if the length of the input traces connected to the device are short. For designs requiring additional radiated emissions attenuation, ferrite bead and common-mode choke selection and placement recommendations are provided.

Several industrial and automotive applications require some type of isolation to protect the digital circuitry from the high-voltage circuit performing a function. Texas Instruments has an extensive portfolio of isolated amplifiers and converters featuring a SiO₂ isolation barrier to help customers address their isolated data conversion needs. Texas instruments’ SiO₂ isolation barrier allows for exceptional reliability, often over 100 years of operation. For more information on TI's SiO₂ isolation barrier, please review the Isolation link. EMI testing is common in these applications to verify the system does not produce radiated emissions that exceed the defined levels which may negatively impact other components or circuits in the system. Please see this application note for a more in-depth description of EMI. The magnitude of acceptable radiation and testing procedure for radiated emissions is put in place by the Comité International Spécial des Perturbations Radio, also known as CISPR. Industrial applications measure according to the CISPR 11 standard, while automotive applications measure to the CISPR 25 standard. For more information on the CISPR standards and their respective magnitudes over frequency, please see this application note.