Information

Design and specifi cations are subject to change without notice. Ask factory for technical specifi cations before purchase and/or use.
Whenever a doubt about safety arises from this product, please contact us immediately for technical consultation.
18
Gold Capacitors Technical Guide
Operating Techniques of Gold Capacitors
Operating Techniques of Gold Capacitors
4-1 Life design
4-1-1 Useful life
Gold capacitors have a useful life-time similar to that of aluminum electrolytic capacitors. The life of a Gold Capacitor
is largely dependent on the operating temperature, humidity, applied voltage, current and backup time requirements.
Therefore, the life of a Gold Capacitor is determined based on the back-up time set by the customer.
4-1-2 Example of expected life
An example of an expected life-time of a Gold Capacitor is shown as follows:
Expected life = Life-time X Temperature factor X Voltage factor X Moisture factor
Note: Life-time is defi ned as the time it takes to reach back-up time set by the customer after applying the rated
maximum temperature and rated voltage to the capacitor.
Example: An F type Gold capacitor, P/N: EECF5R5H105 (Rated at 5.5V, 1.0F), is fully charged at 5.0V D.C. The circuit
requirement is such that it must maintain a memory circuit with a current drain of 10
µA in an ambient temperature of
+40
°C. The memory RTC cut-off voltage is 2.0V D.C.
The back-up time can be calculated from the following equation.
t = CV/i = C x (V
0
-ixR-V
1
)/(I+i
L
) t: Back-up time (s)
C: Capacitance of Gold capacitor (F)
C=0.8F(1.0F-20%), R=50Ω, V
0
=5V, V
1
=2V, i =10µA V0: Applied voltage (V)
V1: Cut-off voltage (V)
Therefore, i: Current during back-up (A)
t = 0.8 x (5-0.0005-2)/(10+2x10
-6
) = 55hours iL: Leakage current (A)
R: Internal resistance (Ω) at 1 kHz
This calculation shows the initial back-up time to be 55hours.
Product Life
The guaranteed life is 1000hours for –30% capacitance change, 4times the internal resistance change at 85°C with
5.5VDC applied. After 1000 hours, the back-up time will be changed to approximately 38 hours.
Temperature factor
To determine the serviceable life of a Gold Capacitor, one can use the Arrenhenius Equation, which states that the
life will double for every 10°C reduction in ambient temperature.
2
(85-40)/10
= 2
4.5
= 22.6
Voltage factor
The capacitance rate of change for each applied voltage becomes smaller when the applied voltage becomes lower.
The time to reach the same change rate at 5V will be 1.1 times longer than 5.5V.