With the increasing popularity of MLCCs (or ceramic capacitors) in electronic circuits due to their low cost and low profile, their inherent piezoelectric effect and the resultant audible noise can become a problem, as more and more electronic devices are handheld.
The multilayer ceramic capacitor (MLCC) has numerous advantages compared to commonly used tantalum electrolytic capacitors, including:
•very low equivalent series resistance (ESR),
•very low equivalent series inductance (ESL),
•lower aging and a high reliability of its dielectric.
However, like all ferroelectric dielectrics, it is affected by the piezoelectric effect: certain materials generate an electric potential or electric field on the surface by mechanical deformation. If the dielectric is now subjected to a varying electric field intensity that operates at a frequency which is located in the audible frequency range of the human ear (20 Hz to 20 kHz), the capacitor produces noise, the so-called audible noise.
A MLCC alone is in most cases not sufficient to generate a problematic or disruptive Sound Pressure Level (SPL). But when it is soldered on a PCB board, the MLCC generates a spring-mass system, which increases or dampens the oscillations depending on the frequencies.
This article investigates and discusses Influences, possible causes, and solutions to reduce audible noise in ceramic capacitors, including:
•Experimental environment and setup
•Signal characteristics influence
•Component characteristics influence
•PCB board influence
•Audible noise in electronic circuitry
•Alternatives to MLCCs
Click to read “Reducing MLCCs’ piezoelectric effects and audible noise ,” which appeared in EE Times-Europe .
About the author
Nicolas Guibourg joined Texas Instruments Germany as systems engineer in 2006, where he works on application support and new product definition for the Display Power Converters group. He has an electrical engineering degree from ISEN – Institut Supérieur de l’Électronique et du Numérique (France).
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