HCPL-3150-360 View Datasheet(PDF) - Avago Technologies
Part Name
Description
MFG CO.
'HCPL-3150-360' PDF : 21 Pages View PDF
The value of 4.25 mA for I in the previous equation was
CC
obtained by derating the ICC max of 5 mA (which occurs
at -40°C) to I max at 90°C (see Figure 7).
CC
Since P for this case is greater than P , Rg must be
O
O(MAX)
increased to reduce the HCPL-3150 power dissipation.
P
=P -P
O(SWITCHING MAX) O(MAX) O(BIAS)
= 154 mW - 85 mW
= 69 mW
From the thermal mode in Figure 28a the LED and detec-
tor IC junction temperatures can be expressed as:
T
JE
=
P
E
x
(TLC||(TLD
+
TDC)
+
TCA)
( ) + P x
D
TLC x TDC
TLC + TDC + TLD
+ TCA
+T
A
( ) T =P
JD E
TLC x TDC
TLC + TDC + TLD
+ TCA
+
Px
D
(TDC||(TLD
+
TLC)
+
TCA)
+
T
A
E
SW(MAX)
= PO(SWITCHINGMAX)
f
= 69 mW = 3.45 μJ
20 kHz
For Qg = 500 nC, from Figure 27, a value of E = 3.45 μJ
SW
gives a Rg = 41 Ω.
Thermal Model (HCPL-3150)
The steady state thermal model for the HCPL-3150 is
shown in Figure 28a. The thermal resistance values given
in this model can be used to calculate the temperatures
at each node for a given operating condition. As shown
by the model, all heat generated flows through TCA which
raises the case temperature TC accordingly. The value of
TCA depends on the conditions of the board design and
is, therefore, determined by the designer. The value of
TCA = 83°C/W was obtained from thermal measure-
ments using a 2.5 x 2.5 inch PC board, with small traces
(no ground plane), a single HCPL-3150 soldered into
the center of the board and still air. The absolute maxi-
mum power dissipation derating specifications assume
a TCAvalue of 83°C/W.
Inserting the values for TLC and TDC shown in Figure 28
gives:
T
JE
=
Px
E
(230°C/W
+
TCA)
+
P x(49°C/W
D
+
TCA)
+
T
A
T
JD
=
P
E
x
(49°C/W
+
TCA)
+
Px
D
(104°C/W
+
TCA)
+
T
A
For example, given P = 45 mW, P = 250 mW, T = 70°C
E
O
A
and TCA = 83°C/W:
T = P x313°C/W + P x132°C/W + T
JE E
D
A
= 45 mWx313°C/W + 250 mW x132°C/W + 70°C = 117°C
TJD = PEx132°C/W + PDx187°C/W + TA
= 45 mWx132C/W + 250 mW x187°C/W + 70°C = 123°C
T and T should be limited to 125°C based on the board
JE
JD
layout and part placement (TCA) specific to the applica-
tion.
θLD = 439°C/W
TJE
TJD
θLC = 391°C/W
θDC = 119°C/W
TC
θCA = 83°C/W*
TA
Figure 28a. Thermal Model.
T = LED junction temperature
JE
T = detector IC junction temperature
JD
T = case temperature measured at the center of the package bottom
C
TLC = LED-to-case thermal resistance
TLD = LED-to-detector thermal resistance
TDC = detector-to-case thermal resistance
TCA = case-to-ambient thermal resistance
TCA will depend on the board design and the placement of the part.
16
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