Multilayer ceramic capacitors (MLCCs) are the workhorses of modern electronics, but their effective capacitance can drop dramatically when a DC voltage is applied. This phenomenon, known as DC bias derating, catches many designers off guard.
Why does it happen?
Class II dielectrics such as X5R and X7R are ferroelectric materials. When a DC electric field is applied, the alignment of ferroelectric domains is progressively exhausted, reducing the permittivity of the dielectric and therefore the measured capacitance.
What you can do about it
- Derate explicitly: use the capacitance vs. DC bias curves from the manufacturer datasheet.
- Use higher voltage ratings: a 50 V X5R part holds its capacitance far better at 12 V than a 16 V part.
- Consider C0G/NP0: for precision or timing circuits, class I dielectrics have negligible DC bias dependence.
At ANFULLY we stock a wide range of MLCCs from leading manufacturers, with datasheet curves available on request. Contact our engineers for help selecting the right part for your DC-DC, filtering or decoupling application.
This article was written by fifi. Reproduction with attribution is welcome.
Comments
0