STK433-090-E

No. A1248-9/11

STK433-100 Series Application Explanation

The protection circuit application for the STK433-100sr consists of the following blocks (blocks (1) to (4)).

(1) Standby control circuit block

(2) Load short-circuit detection block

(3) Latch-up circuit block

(4) DC voltage protection block

1) Standby control circuit block

(Reference example) STK433-100 series test circuit (when +5V is applied to Stand-by control.)

Concerning pin 13 reference voltage VST

<1> Operation mode

The switching transistor in the bias circuit turns on and places the amplifier into the operating mode when the

current flowing into pin 13 (IST) becomes 0.25mA or greater.

<2> Standby mode

When the current flowing into pin 13 (IST) is stopped (=0mA), the switching transistor in the bias circuit turns

off, placing the amplifier into the standby mode.

(*1) The current limiting resistor (R1) must be used to ensure that the current flowing into the stand-by pin

(pin 13) does not exceed its maximum rated value IST max.

(*2) The pop noise level when the power is turned on can be reduced by setting the time constant with a

capacitor in operating mode.

(*3) Determines the time constant at which the capacitor (*3) is discharged in standby mode.

2

3

4

5

6

7

8

9

10

11

12

13

14

1

15

OUT Ch1

STK433-100 series

56k

Ω

IST

+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

(2) Load short

detection part

22k

Ω

56k

Ω

1k

Ω

0.1

μF10kΩ

100k

Ω

1k

Ω

33k

Ω

2k

Ω

(*1) R1

ex) 13k

Ω

33

μF

OUT Ch2

82k

Ω

82k

Ω

100

k

Ω

22

μF

22

μF

1) Stand-by control circuit part

H: Operation mode (+5V)

L: Stand-by mode (0V)

Point.B

Point.B

Point.C

Point.C

Tr1

Tr2

Stand-by Circuit

in Pre Driver IC

SW transistor

ΔVBE

(*2)

ex) +5V

(*4) R2

I2

I3

(3) Latch-up

circuit part

(4) DC offset

protection

Tr4

Tr5

Tr3

Tr5

Tr6

-VCC

2

3

4

5

6

7

8

9

10

11

12

13

14

1

15

STK433-100series

+VCC

Ch1

IN

Ch1

NF

Ch2

IN

Ch2

NF

Ch2

OUT

Ch1

OUT

-VCC

GND

+PRE

ST-BY

Ch1

OUT

Ch2

OUT

-PRE

1k

Ω (*3)

33k

Ω

2k

Ω (*3)

(*1) R1

13k

Ω

33

μF

(*2)

1) Stand-by control

H: Operation mode (+5V)

L: Stand-by mode (0V)

ΔVBE

VST

Sink current IST

SUB

ΔVBE

ex) Stand-by control voltage=+5V

IST=(VST-VBE*2)/R1

=(5-0.6*2)/13k

Ω

≈0.3(mA)

Stand-by Circuit

in Pre Driver IC