Type EDL
Electric Double Layer Supercapacitors
How to Select an Electric Double Layer Supercapacitor
Estimated initial back-up time
Back-up time for Type EDL Electric Double Layer Supercapacitors decreases with use and over time
especially when the current is large or operating at high temperature. Be sure to specify extra back-up
time initially to allow for product changes.
Select the optimum supercapacitor according to applied current.
The internal resistance of the supercapacitor prevents drawing high discharge currents. Select the
supercapacitor capable of delivering the peak current at switchover to back-up mode using the follow-
ing table.
Series
SG, SD, NF
F
EN
HW
Maximum Operating (Discharge) Current
0.047 F
200 µA
200 µA
–
–
0.1 F to 0.33 F
300 µA
300 µA
10 µA
–
0.47 F to 1.5 F
1 mA
300 µA
–
100 mA
3.3 F to 4.7 F
–
–
–
300 mA
10 F to 50 F
–
–
–
1A
Back-up Time Example
Back-up time is the time it takes for the applied voltage to decay to the cut-off voltage set by the user
after applying the application’s maximum voltage at application maximum temperature.
Example: An F Type EDL, P/N EDLF105B5R5C (Rated at 5.5 V, 1.0 F) is charged to 5.0 Vdc. 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 ºC. The memory RTC cut-off voltage is 2.0 Vdc.
Using minimum capacitance, calculate the back-up time as
follows:
t = CΔV ⁄ I = C[V
0
–(i
•
R)–V
1
] ⁄ (i+i
L
)
C = 1.0 F–20% = 0.8 F, R=50 Ω, V
0
=5 V. V
1
=2 V, i=10 µA
t: Back-up time (s)
C: Capacitance of Type EDL (F)
V
0
: Applied voltage (V)
V
1
: Cut-off voltage (V)
i: Current during back-up (A)
i
L
: Leakage current (A)
R: Internal resistance (Ω) at 1 kHz
Therefore,
t = 0.8 (5–0.0005–2) ⁄ (10+2) ⁄ 10
–6
= 55 hours
And thus the initial back-up time is 55 hours. After 1000 hours,
Life Design for Electric Double Layer Supercapacitors
Type EDL supercapacitors have a useful lifetime that decreases with increasing operating temperature,
humidity, applied-voltage, current and backup-time requirements.
Expected lifetime is the product of four factors:
Expected Life = (Lifetime)•(Temperature Factor)•(Voltage Factor)•(Moisture Factor)
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