Avago Technologies ACPL-224-500E - Manual (Page 15)

AV02-4387EN 13 Avago Technologies
High-reliability LEDs in Avago
Optocouplers
As a further demonstration of the
reliability and robustness of Avago
LEDs, Avago Technologies’ isolation
products portfolio is able to add
automotive grade optocouplers.
As part of the R2Coupler™ family,
these AEC-Q100 qualified automo-
tive grade optocouplers address
all emerging automotive isolation
applications, particularly in applica-
tions requiring reliable long term
operation at high ambient tempera-
Figure 15 illustrates the trend of LED
degradation performance at differ-
ent forward LED input current (IF)
for AlGaAs (type 2) LED. As the graph
shows, the LED has minimal deg-
radation across the optocoupler’s
recommended operating range for
IF and for over a 20+ year lifetime,
the degradation is less than 10%. In
general, there are three basic factors
to consider maximizing the LED op-
erating lifetime:
1. Operate the LED at a lower IF.
2. Operate at lower duty cycle (less
than 100%).
3. Operate at an ambient tempera-
ture of less than 125°C.
Figure 15. CTR degradation performance vs field years for AlGaAs (Type 2) LED at different I
F
(50% duty cycle, T
A
=80 °C)
Figure 14c. CTR degradation performance vs field years for GaAsP LED (operating I
F
=16mA, 50% duty cycle, T
A
=80 °C)
tures up to 125°C. The LEDs used for
R2Coupler™ optocouplers typically
drops by <20% at 125°C, whereas
commercially available (consumer
grade and general purpose indus-
trial) infrared LEDs typically experi-
ence a drop of up to 60% at 125°C.
As this is beyond the recommended
temperature range for commer-
cially available LEDs, it highlights
the importance that only specially
designed LEDs for high temperature
operation can be used for automo-
tive grade optocouplers.
Calculate the LED Lifetime Performance
in Optocouplers to Predict Reliability
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
110%
CTR Degradation
Field Years
0 5 10 15 20 25 30
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
110%
CTR Degradation
Field Years
GaAs LED Performance vs Field Years
0 5 10 15 20 25 30
20 mA
15 mA
10 mA
5 mA
3 mA
Ave
Ave-3Std (worst-case)
AlGaAs (type 2) LED degradation at different iF
Note: I
F
=20mA condition projects
till 22.6 field years due to actual
stress data collected up to 10khrs.
This does not mean LED fails at
22.6 projected field years. Longer
>10khrs stress data points will be
needed for projecting longer field
year