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Data subject to change. Copyright © 2005-2015 Avago Technologies. All rights reserved.
AV02-4194EN - May 22, 2015
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as parts, components or assemblies for the planning, construction, maintenenace or direct operation of a
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make claims against Avago or its suppliers, for all loss, damage, expense or liability in connection with such use.
3. Application precautions
a. Drive current of the LED must not exceed the
maximum allowable limit across temperature as
stated in the datasheet. Constant current driving is
recommended to ensure consistent performance.
b. The LED is not intended for reverse bias. Do use
other appropriate components for such a purpose.
When driving the LED in matrix form, make sure the
reverse bias voltage does not exceed the allowable
limit for the LED.
c. Do not use the LED in the vicinity of material with
sulfur content, in an environment of high gaseous
sulfur compound and corrosive elements. Examples
of materials that may contain sulfur are rubber
gasket, Room Temperature Vulcanizing (RTV)
silicone rubber, rubber gloves, and so on. Prolonged
exposure to such an environment may aect the
optical characteristics and product life.
d. Avoid a rapid change in ambient temperature
especially in a high humidity environment as this
will cause condensation on the LED.
4. Thermal management
Optical, electrical and reliability characteristics of LED
are aected by temperature. The junction temperature
(T
J
) of the LED must be kept below the allowable limit
at all times. T
J
can be calculated as follows:
T
J
= T
A
+ R
qJ-A
× I
F
× V
Fmax
where
T
A
= ambient temperature [°C]
R
qJ-A
= thermal resistance from LED junction to ambi-
ent [°C/W]
I
F
= forward current [A]
V
Fmax
= maximum forward voltage [V]
The complication of using this formula lies in T
A
and
R
qJ-A
. Actual T
A
is sometimes subjective and hard to de-
termine. R
qJ-A
varies from system to system depending
on design and is usually not known.
Another way of calculating T
J
is by using solder point
temperature T
S
as shown as follows:
T
J
= T
S
+ R
qJ-S
× I
F
× V
Fmax
where
T
S
= LED solder point temperature as shown in the fol-
lowing illustration [°C]
R
qJ-S
= thermal resistance from junction to solder point
[°C/W]
T
S
can be easily measured by having a thermocouple
mounted on the soldering joint, as shown in this illus-
tration, while R
qJ-S
is provided in the datasheet. Please
verify the T
S
of the LED in the nal product to ensure
that the LEDs are operated within all maximum ratings
stated in the datasheet.
5. Eye safety precautions
LEDs may pose optical hazards when in operation. It is
not advisable to view directly at operating LEDs as it
may be harmful to the eyes. For safety reasons, use ap-
propriate shielding or personal protective equipment.
Ts point
(PIN 4)
