TAP/TEP Technical Summary and
Application Guidelines
SECTION 2:
AC OPERATION — RIPPLE VOLTAGE AND RIPPLE CURRENT
2.1 RIPPLE RATINGS (AC)
In an AC application heat is generated within the capacitor
by both the AC component of the signal (which will depend
upon signal form, amplitude and frequency), and by the
DC leakage. For practical purposes the second factor is
insignificant. The actual power dissipated in the capacitor is
calculated using the formula:
affect the values quoted below. It is recommended that
temperature measurements are made on devices during
operating conditions to ensure that the temperature differential
between the device and the ambient temperature is less than
10°C up to 85°C and less than 2°C between 85°C and 125°C.
Derating factors for temperatures above 25°C are also shown
below. The maximum permissible proven dissipation should be
multiplied by the appropriate derating factor.
E2 R
P = I2 R =
Z2
I = rms ripple current, amperes
R = equivalent series resistance, ohms
E = rms ripple voltage, volts
P = power dissipated, watts
Z = impedance, ohms, at frequency under
consideration
For certain applications, e.g., power supply filtering, it may
be desirable to obtain a screened level of ESR to enable
higher ripple currents to be handled. Please contact our
applications desk for information.
2.4 POWER DISSIPATION RATINGS
(IN FREE AIR)
Using this formula it is possible to calculate the maximum
AC ripple current and voltage permissible for a particular
application.
TAR – Molded Axial
Temperature
Case
size
Q
R
S
W
Max. power
2.2 MAXIMUM AC RIPPLE VOLTAGE
derating factors
dissipation (W)
(EMAX
)
Temp. °C
Factor
0.065
0.075
0.09
From the previous equation:
+25
+85
+125
1.0
0.6
0.4
P max
R
E(max) = Z
0.105
ꢂ
TAA – Hermetically Sealed Axial
where Pmax is the maximum permissible ripple voltage as listed
for the product under consideration (see table).
Temperature
derating factors
Case
size
Max. power
dissipation (W)
However, care must be taken to ensure that:
1. The DC working voltage of the capacitor must not be
exceeded by the sum of the positive peak of the applied
AC voltage and the DC bias voltage.
Temp. °C Factor
A
B
C
D
0.09
0.10
0.125
0.18
+20
+85
+125
1.0
0.9
0.4
2. The sum of the applied DC bias voltage and the negative
peak of the AC voltage must not allow a voltage reversal
in excess of that defined in the sector, ‘Reverse Voltage’.
TAP/TEP – Resin Dipped Radial
Temperature
derating factors
Case
size
A
B
C
D
E
F
G
H
J
K
L
M/N
P
R
Max. power
dissipation (W)
2.3 MAXIMUM PERMISSIBLE POWER
DISSIPATION (WATTS) @ 25°C
The maximum power dissipation at 25°C has been calculated
for the various series and are shown in Section 2.4, together
with temperature derating factors up to 125°C.
Temp. °C Factor
0.045
0.05
0.055
0.06
0.065
0.075
0.08
0.085
0.09
0.1
0.11
0.12
0.13
0.14
+25
+85
+125
1.0
0.4
0.09
For leaded components the values are calculated for parts
supported in air by their leads (free space dissipation).
The ripple ratings are set by defining the maximum tempera-
ture rise to be allowed under worst case conditions, i.e.,
with resistive losses at their maximum limit. This differential
is normally 10°C at room temperature dropping to 2°C at
125°C. In application circuit layout, thermal management,
available ventilation, and signal waveform may significantly
154 ■ MAY 2013
KYOCERA AVX [ KYOCERA AVX ]
