STK433-070-E

No. A1488-7/11

Evaluation Board Characteristics

[Thermal Design Example for STK433-070-E (RL = 6Ω)]

The thermal resistance,

θc-a, of the heat sink for total power dissipation, Pd, within the hybrid IC is determined as

follows.

Condition 1: The hybrid IC substrate temperature, Tc, must not exceed 125

°C.

Pd

× θc-a + Ta < 125°C ................................................................................................. (1)

Ta: Guaranteed ambient temperature for the end product

Condition 2: The junction temperature, Tj, of each power transistor must not exceed 150

°C.

Pd

× θc-a + Pd/N × θj-c + Ta < 150°C .......................................................................... (2)

N: Number of power transistors

θj-c: Thermal resistance per power transistor

However, the power dissipation, Pd, for the power transistors shall be allocated equally among the number of power

transistors.

The following inequalities result from solving equations (1) and (2) for

θc-a.

θc-a < (125 − Ta)/Pd ...................................................................................................... (1)'

θc-a < (150 − Ta)/Pd − θj-c/N ........................................................................................ (2)'

Values that satisfy these two inequalities at the same time represent the required heat sink thermal resistance.

When the following specifications have been stipulated, the required heat sink thermal resistance can be determined

from formulas (1)' and (2)' .

• Supply voltage

VCC

• Load resistance

RL

• Guaranteed ambient temperature

Ta

PO - VCC

Supply voltage, VCC - ±V

Pd - PO

Output power, PO/ch - W

THD - PO

PO - f

Frequency, f - Hz

Output power, PO/ch - W

ITF02680

0

100

90

80

70

60

50

40

30

20

10

10

15

20

30

25

35

40

ITF02679

0

1.0

0.1

100

70

90

80

50

60

30

40

10

20

23

5

7

23

5

7

10

23

5

7 100

VG=30dB

Rg=600

Ω

RL=6Ω

Tc=25

°C

f=1kHz

2ch Drive

VCC=±29V

VG=30dB

f=1kHz

Rg=600

Ω

Tc=25

°C

RL=6Ω

2ch Drive

VCC=±29V

VG=30dB

Rg=600

Ω

Tc=25

°C

RL=6Ω

2ch Drive

ITF02681

1k

10

100

100

90

80

50

60

70

30

40

20

10

0

2 3

57

2 3

5 7

2 3

57

2 3

57

10k

100k

THD=10%

THD=0.4%

ITF02678

0.001

1.0

0.1

0.01

7

5

3

2

7

5

3

2

7

5

3

2

7

5

3

2

7

5

3

2

0.1

1.0

100

10

23

5

7

23

5

7

10

23

5

7 100

VCC=±29V

VG=30dB

Rg=600

Ω

Tc=25

°C

RL=6Ω

2ch Drive

f=20kHz

1kHz

THD

=0

.4%