Phycomp
Product specification
Surface mount ceramic
multilayer capacitors
Class 1, NP0 50/100/200/500 V
Noble Metal Electrode
MLB198
500
handbook, halfpage
ESR
(mΩ)
300
200
10 pF
47 pF
100
C
ESR
L
100 pF
MEA609
220 pF
50
30
20
10
50
100
200
300
500
f (MHz)
C = capacitance.
ESR = equivalent series resistance which is determined by the
energy dissipation mechanisms (in the dielectric material as well
as in the electrodes).
Case size 1206.
High voltage 500 V.
L = equivalent series self-inductance.
Fig.15 Typicalequivalent series resistance as
a function of frequency.
Fig.16 Equivalent series representation of a CMC.
HIGH FREQUENCY BEHAVIOUR OF CERAMIC
MULTILAYER CAPACITORS
Because of the inductance L, associated with the CMC,
there will be a frequency at which the inductive reactance
will be equal to the reactance of the capacitor.
Ceramic multilayer capacitors (CMC) are suitable for use
at high frequencies. At frequencies below the series
resonance frequency, the CMC can be represented by an
equivalent circuit as shown in Fig.16.
This is known as the series resonance frequency (SRF)
and is given by:
1
SRF =
-------------------
2π LC
In general, the quantities C, ESR and L are frequency
dependent. For most applications, C and L can be
regarded as frequency independent below 1 GHz.
At the SRF, the CMC will appear as a small resistor.
The transmission loss through the CMC at this series
resonance frequency will be low.
The equivalent series self-inductance L is:
• Independent of the dielectric material.
Using the values of C, L = 1 nH and the ESR at a specific
frequency (f), two often used quantities can be derived.
• Dependent on the size of the capacitor, it increases with
increasing length and decreases with increasing width
or thickness of the product.
The impedance (Z) is given by:
1 – (2πf)2LC
Z =
+ ESR
------------------------------------
• The value of L is approximately:
– 0.6 nH for case size 0603
2jπfC
The quality factor (Q) is given by:
– 1 nH for case sizes 0805, 1206 and 1210
– 1.5 nH for case sizes 1812.
1 – (2πf)2LC
Q =
--------------------------------------
2πfESRC
These figures are accurate to within 20%.
2000 Sep 11
15