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AV02-4500EN - October 9, 2014
Figure 17. Diagram of ACPL-K30T for measurement
R
11
: Thermal Resistance of Die1 due to heating of Die1
R
12
: Thermal Resistance of Die1 due to heating of Die2.
R
21
: Thermal Resistance of Die2 due to heating of Die1.
R
22
: Thermal Resistance of Die2 due to heating of Die2.
P
1
: Power dissipation of Die1 (W).
P
2
: Power dissipation of Die2 (W).
T
1
: Junction temperature of Die1 due to heat from all dice (°C).
T
2
: Junction temperature of Die2 due to heat from all dice.
T
A
: Ambient temperature.
∆T
1
: Temperature dierence between Die1 junction and ambient (°C).
∆T
2
: Temperature deference between Die2 junction and ambient (°C).
T
1
= R
11
x P
1
+ R
12
x P
2
+ T
A
T
2
= R
21
x P
1
+ R
22
x P
2
+ T
A
Measurement data on a low K (connectivity) board:
R
11
= 258 °C/W
R
12
= 121 °C/W
R21 = 119 °C/W
R
22
= 201 °C/W
Measurement data on a high K (connectivity) board:
R
11
= 194 °C/W
R
12
= 59 °C/W
R
21
= 53 °C/W
R
22
= 136 °C/W
R
11
R
12
•
P
1
=
∆T
1
R
21
R
22
P
2
∆T
2
8
7
6
5
1
2
3
4
Die 1:
LED
Die 2:
Detector
Thermal Resistance Model for ACPL-K30T
The diagram of ACPL-K30T for measurement is shown in
Figure 17. Here, one die is heated rst and the tempera-
tures of all the dice are recorded after thermal equilibrium
is reached. Then, the second die is heated and all the dice
temperatures are recorded. With the known ambient tem-
perature, the die junction temperature and power dissipa-
tion, the thermal resistance can be calculated. The ther-
mal resistance calculation can be cast in matrix form. This
yields a 2 by 2 matrix for our case of two heat sources.
