NCV7708

http://onsemi.com

14

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)

0.000001

0.00001

0.0001

0.001

0.01

0.1

1.0

10

100

1000

SOIC 28−lead Thermal RC Network Models

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.