Nemco Electronics Performance Info - Manual (Page 4)

General Performance Information
z Tan δ (at 120 Hz/25°C) (DF)
Tangent of Loss Angle is a measurement of the energy loss in the capacitor. Terms also used are power factor, loss factor,
quality factor, “Q” (the reciprocal of DF) and DF which is the measurement of Tan
δ expressed as a percentage. Tan δ is the
power loss of the capacitor divided by its reactive power at a sinusoidal voltage of a specified frequency. Measurement is
carried out at +25°C and 120Hz with 2.2V DC bias max., with an a.c. voltage free of harmonics. The value of Tan
δ
is temperature and frequency dependent. DF increases with increasing frequency. DF loses its importance at higher
frequencies where impedance and ESR are the normal parameters of concern.
Typical Curve Typical Curve
Dissipation Factor (D.F.) vs. Temperature Dissipation Factor (D.F.) vs. Frequency
Temperature °C Frequency
Tan δ (DF) values are indicated in part number tables. The values shown in the part number tables are the limits met by the
component after soldering onto the substrate.
Tan
δ (DF) =
R = 2
πƒCR
Tan
δ (DF) = Dissipation factor
X
c
R = ESR (ohms)
X
c
= Capacitive reactance (ohms)
ƒ = Frequency (Hertz)
C = Series capacitance (Farads)
z Impedance Impedance is the ratio of voltage to current at a specified frequency. Three factors contribute to the
impedance of a tantalum capacitor; the resistance of the semiconductor layer; the capacitance value and the
inductance of the electrodes and terminations. At high frequencies the inductance of the terminations becomes
a limiting factor. The temperature and frequency behavior of these three factors of impedance determine the
behavior of the impedance. The impedance is measured at +25°C and 100KHz. There is unavoidable
inductance as well as resistance in all capacitors. At some point in frequency, the reactance stops being capac-
itive and becomes inductive. This frequency is the self resonant point and typically falls between 0.5 - 5MHz
depending on the rating. In solid tantalum capacitors, resonance is damped by the ESR and a smooth transi-
tion from capacitive to inductive reactance occurs. Total Impedance of the capacitor can be viewed as:
Below resonance - The vector sum of capacitive reactance. X
c
= 1 ohm and ESR
2
πƒc
Above resonance - The vector sum of inductive reactance. ( X
L
= 2
πƒL ) and ESR
ƒ = frequency, Hertz C = capacitance,farad L = inductance, Henries
z ESR Equivalent Series Resistance (ESR) is the preferred high frequency statement of the unavoidable resistance
appearing in tantalum capacitors. Maximum limits for 100 kHz ESR are listed in the part number tables. NOTE:
Nemco LSR series is specifically designed for low ESR performance. Resistance losses occur in all practical forms
of capacitors. These are made up from several different mechanisms, including resistance in components and
contacts, viscous forces within the dielectric and defects producing bypass current paths. To express the effect of
these losses they are considered as the ESR of the capacitor. The ESR is measured at +25°C and 100KHz. The
ESR is frequency dependent and can be found by using the relationship;
ESR = Tan δ
2 πƒC
Where ƒ is the frequency in Hertz, and C is the capacitance in farads.
ESR is one of the contributing factors to impedance. At high frequencies (100KHz and above) it becomes the
dominant factor. ESR and impedance become almost identical, impedance being only marginally higher.
DF % DF %
( )