Capacitors

Reading time : 4 minutes
Published on 20 Apr 2020 - Updated on 07 Jan 2021

Information and tips about capacitors

Voltage derating

Tantalum with MNO2 dielectric

Maximum voltage shall not excess in any case rated voltage.
Application continuous voltage shall be maximum 50% of rated voltage.
Maximum current shall be caculated carefully

Conductive polymer

Maximum voltage shall not excess in any case rated voltage.
A 90% derating shall be used if voltage rating of the capacitor is 10V or lower.
A 80% derating shall be used if voltage rating of the capacitor is 16V or higher.

Ceramic / MLCC

Maximum voltage shall not excess in any case rated voltage
No derating required

Aluminium

Maximum voltage shall not excess in any case rated voltage
No derating required
Operating temperature will greatly affect lifetime, power dissipation shall be verified.

Guideline for MLCC

This is a guideline for ceramic SMT capacitors when designing PCB.
General idea is to use X7R or X5R dielectric type.

Maximum values by package and voltage

0201

  • 10 nF 10 V
  • 1 nF 25 V

0402

  • 1 µF 10 V
  • 220 nF 16 V
  • 100 nF 25 V

0603

  • 10 µF 6.3 V
  • 2.2 µF 10 V
  • 1 µF 25 V

0805

  • 10 µF 10 V
  • 4.7 µF 25 V

1206

  • 100 µF 6.3 V
  • 22 µF 16 V
  • 10 µF 25 V

1210

  • 47 µF 16 V
  • 22 µF 25 V

MLCC capacitors dielectric

MLCC capacitors are sorted in three different classes depending on the dielectric.
Common dielectrics are C0G, X5R, Z5U

For class 2 and class 3, dielectric is defined by three two letters and one number :

  • First character defines the lowest temperature
  • Second character defines the maximum temperature
  • Third character defines the capacitance variation over whole temperature range

Here is chart showing capacitance variation depending on temperature :

Chart showing capacitors value depending on temperature and dielectric
Ceramic capacitors dielectric comparison

Class 1 C0G, U2J

Class 1 capacitors are “ultra-stable”, this class of capacitors is suitable for oscillators, clocks, analog chains where precision is required.

Theses capacitors are not affected by piezoelectric singing effect.

Maximum value is 1nF
Common dieletrics are C0G, U2J

First CharacterTemperature coefficient (ppm/°C)Second characterTemperature coefficient multiplierThird characterTolerance of temperature coefficient (ppm/°C)
C00-1G30
B0.31-10H60
L0.82-100J120
A0.93-1000K250
M1.04-10000L500
P1.55+1M1000
R2.26+10N2500
S3.37+100
T4.78+1000
U7.59+10000

Class 2 X7R, X5R, X6S

Class 2 capacitors are general use bulk and bypass capacitors.

Theses capacitors are affected by pizoelectric singing effect.

Maximum value is 100uF
Common dieletrics are X7R, X5R, X6S

First CharacterLow temperature (°C)Second characterHigh temperature (°C)Third characterTolerance of temperature coefficient (%)
Z+102+45A+/- 1.0
Y-304+65B+/- 1.5
X-555+85C+/- 2.2
6+105D+/- 3.3
7+125E+/- 4.7
8+150F+/- 7.5
9+200P+/- 10
R+/- 15
S+/- 22
L+15 to -40
T (class 3)+22 to -33
U (class 3)+22 to -56
V (class 3)+22 to -82

Class 3 Z5U and Y5V

Class 3 capacitor are reserved for very low cost application. Generally class 3 capacitors shall be avoided except if you know what you are doing or you want to optimize every cent of your design

Theses capacitors are affected by pizoelectric singing effect.

Maximum value is 100uF

Piezoelectric effect

Capacitor deformation due to piezoelectric effect
Ceramic piezoelectric effect

Sometimes capacitor are producing sound. Voltage and current inside capacitor can make it vibrate. This is mainly caused by voltage ripple and current ripple. Capacitors making sound happens when current ripple frequency is in the audio band (20Hz to 20kHz). This is something classic when DC/DC are in light load mode (pulse skipping).

Class 2 and Class 3 capacitors are concerned by this effect. Class 1 capacitors does not produce it

MLCC Dielectric differences on Kemet blog

Source files

Singing ceramic capacitors application note from TDK