STK433-090-E

No. A1248-8/11

[Example]

When the IC supply voltage, VCC, is ±33V and RL is 6Ω, the total power dissipation, Pd, within the hybrid IC, will

be a maximum of 75W at 1kHz for a continuous sine wave signal according to the Pd-PO characteristics.

For the music signals normally handled by audio amplifiers, a value of 1/8PO max is generally used for Pd as an

estimate of the power dissipation based on the type of continuous signal. (Note that the factor used may differ

depending on the safety standard used.)

This is:

Pd

≈ 59.0W

(when 1/8PO max. = 10W, PO max. = 80W).

The number of power transistors in audio amplifier block of these hybrid ICs, N, is 4, and the thermal resistance per

transistor,

θj-c, is 2.1°C/W. Therefore, the required heat sink thermal resistance for a guaranteed ambient temperature,

Ta, of 50

°C will be as follows.

From formula (1)'

θc-a < (125 − 50)/59.0

< 1.27

From formula (2)'

θc-a < (150 − 50)/59.0 − 2.1/4

< 1.17

Therefore, the value of 1.17

°C/W, which satisfies both of these formulae, is the required thermal resistance of the heat

sink.

Note that this thermal design example assumes the use of a constant-voltage power supply, and is therefore not a

verified design for any particular user’s end product.

STK433-100 Series Standby Control, Mute Control, Load-short Protection & DC

offset Protection application

2

3

4

5

6

7

8

9

10

11

12

13

14

1

15

Ch1 OUT

GND

+VCC

-VCC

STK433-100 series

ST-BY

56k

Ω

GND

Ch2 IN

GND

Ch1 IN

+VCC

Ch1

IN

Ch1

NF

Ch2

IN

Ch2

NF

Ch2

OUT

Ch1

OUT

-VCC

SUB

GND

+PRE

ST-BY

Ch1

OUT

Ch2

OUT

-PRE

6.8k

Ω

56k

Ω

6.8k

Ω

Load short

protection

circuit

22k

Ω

56k

Ω

1k

Ω

0.1

μF

10k

Ω 100kΩ

R1

(*1)

1k

Ω

33k

Ω

2k

Ω

(*1)

13k

Ω

33

μF

/10V

10k

Ω

10k

Ω

10k

Ω

2.2k

Ω

V1

GND

Ch2 OUT

82k

Ω

82k

Ω

100

k

Ω

22

μF

22

μF

PLAY

MUTE

ST-BY

MUTE

+5V

+5V

Standby

Control

Mute

Control

Mute Control

H: Single Mute

L: Normal

Stand-by Control (ex)

H: Operation Mode (+5V)

L: Stand-by Mode (0V)

DC offset protection

(*1) The voltage applied to the Stand-by pin (#13) must not exceed the

maximum rated value (VST max).

Latch up

circuit