STK433-290-E

No. A1630-8/13

Evaluation Board Characteristics

[Thermal Design Example for STK433-290-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

ITF02734

10

20

30

40

50

TH

D=

0.4

%

(f=

20

kH

z)

TH

D

=0

.4

%

(f

=1

kH

z)

ITF02733

0

1.0

0.1

140

120

100

80

60

40

20

0

140

120

100

80

60

40

20

23

5 7

23

5 7

10

2 3

57

2 3

57

100

1000

ITF02732

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

23

5 7

23

5 7

10

100

1000

VCC=±33V

RL=6Ω

VG=30dB

3ch Drive

Rg=600

Ω

Tc=25

°C

Ch1 measurement

RL=6Ω

3ch Drive

VG=30dB

Rg=600

Ω

Tc=25

°C

Ch1 measurement

VCC=±33V

f=1kHz

RL=6Ω

VG=30dB

Rg=600

Ω

Tc=25

°C

3ch Drive

VCC=±33V

RL=6Ω

VG=30dB

Rg=600

Ω

Tc=25

°C

3ch Drive

Ch1 measurement

f=20kHz

f=1kHz

ITF02735

1k

10

100

140

120

40

60

80

100

20

0

2 3

5 7

2 3

57

2 3

57

2 3

5 7

10k

100k

THD=10%

THD=0.4%