NCV7708
http://onsemi.com
14
Cu_Area = 986 mm
2
1 oz 1 S
D = 0.50
D = 0.20
D = 0.10
D = 0.05
D = 0.01
Figure 10. SOIC 28−Lead Thermal Duty Cycle Curves on 1, Spreader Test Board
100
10
1.0
0.1
0.01
PULSE DURATION (sec)
R(t) (°C/W)
0.000001 0.00001 0.0001 0.001 0.01 0.1 1.0 10 100 1000
SOIC 28−lead Thermal RC Network Models
239 mm
2
986 mm
2
239 mm
2
986 mm
2
Cu
Area
Cauer Network Foster Network
C’s C’s Units Tau Tau Units
2.68E−05 2.68E−05 W−s/C 1.00E−06 1.00E−06 sec
1.02E−04 1.02E−04 W−s/C 1.00E−05 1.00E−05 sec
2.82E−04 2.84E−04 W−s/C 1.00E−04 1.00E−04 sec
9.58E−04 9.73E−04 W−s/C 5.00E−04 5.00E−04 sec
2.72E−03 2.63E−03 W−s/C 1.00E−03 1.00E−03 sec
2.02E−03 1.95E−03 W−s/C 1.00E−02 1.00E−02 sec
2.93E−02 3.12E−02 W−s/C 8.00E−02 8.00E−02 sec
0.116 0.091 W−s/C 4.00E−01 4.00E−01 sec
0.16 0.21 W−s/C 2.00E+00 2.00E+00 sec
1 1 W−s/C 6.00E+01 5.50E+01 sec
R’s R’s R’s R’s
0.048 0.048 °C/W 2.84E−02 2.84E−02 °C/W
0.115 0.115 °C/W 6.14E−02 6.14E−02 °C/W
0.352 0.349 °C/W 1.94E−01 1.94E−01 °C/W
0.777 0.776 °C/W 0.100 0.100 °C/W
0.599 0.630 °C/W 0.500 0.480 °C/W
1.677 1.667 °C/W 1.839 1.933 °C/W
2.968 3.151 °C/W 2.207 1.836 °C/W
6.424 5.527 °C/W 1.249 2.291 °C/W
6.940 6.689 °C/W 8.225 8.000 °C/W
53.503 36.970 °C/W 59.000 41.000 °C/W
Bold face items in the Cauer network above, represent the package without the external thermal system. The Bold face items
in the Foster network are computed by the square root of time constant R(t) = 28.4 * sqrt(time(sec)). The constant is derived
based on the active area of the device with silicon and epoxy at the interface of the heat generation.
