HCPL3120000E AVAGO TECH, HCPL3120000E Datasheet - Page 20

• Manufacturer Part Number: HCPL3120000E
• Manufacturer: AVAGO TECH

Thermal Model
(Discussion applies to
HCPL-3120, HCPL-J312
and HCNW3120)
The steady state thermal model
for the HCPL-3120 is shown in
Figure 28. The thermal resistance
values given in this model can be
used to calculate the tempera-
tures at each node for a given
operating condition. As shown by
the model, all heat generated
flows through
the case temperature T
accordingly. The value of
depends on the conditions of the
board design and is, therefore,
determined by the designer. The
value of
obtained from thermal measure-
ments using a 2.5 x 2.5 inch PC
Figure 28. Thermal Model.
LC
= 467 °C/W
T
JE
CA
LD
= 83 C/W was
= 442 °C/W
T
CA
C
which raises
CA
T
A
= 83 °C/W*
T
DC
C
JD
= 126 °C/W
CA
board, with small traces (no
ground plane), a single HCPL-
3120 soldered into the center of
the board and still air. The
absolute maximum power
dissipation derating specifications
assume a
From the thermal mode in Figure
28 the LED and detector IC
junction temperatures can be
expressed as:
T
+ P
+ T
T
+ P
T
JE
JD
T
T
DC
LC
LD
CA
CA
JD
JE
C
D
= P
= P
D
A
= LED junction temperature
= detector IC junction temperature
= case temperature measured at the center of the package bottom
= LED-to-case thermal resistance
= LED-to-detector thermal resistance
= detector-to-case thermal resistance
= case-to-ambient thermal resistance
will depend on the board design and the placement of the part.
(
(
E
E
DC
–––––––––––––––– +
(
(
LC
||(
––––––––––––––– +
CA
LC
+
LC
LC
value of 83 C/W.
LD
||(
+
LC
*
+
DC
LD
DC
DC
+
LC
+
DC
+
) +
LD
DC
LD
) +
CA
) + T
CA
CA
CA
)
)
)
A
20
Inserting the values for
T
T
For example, given P
P
= 83 C/W:
T
T
T
T
T
125 C based on the board layout
and part placement (
to the application.
A
A
DC
JE
JD
JE
JD
O
JE
= 250 mW, T
= P
= P
+ P
+ P
= 45 mW 339 C/W + 250 m
= 45 mW 140C/W + 250 m
= P
and T
= P
shown in Figure 28 gives:
E
140 C/W + 70 C = 120 C
E
194 C/W + 70 C = 125 C
D
D
E
E
339 C/W + P
140 C/W + P
(57 C/W +
(111 C/W +
(256 C/W +
(57 C/W +
JD
should be limited to
A
= 70 C and
D
D
E
CA
CA
CA
140 C/W +
194 C/W +
= 45 mW,
CA
CA
) + T
) specific
)
LC
) + T
)
and
A
W
A
W
CA