2006. 4. 20

4/6

KIB3402F

Revision No : 0

APPLICATION INFORMATION

Inductor Selection

A 4.7 H inductor is sufficient for most application. The efficiency

comprison of different value inductors help you design your

application circuits.

Capacitor Selection

A 1

input capacitor and output capacitor above 1

are

sufficient for most KIB3402F application.

Diode Selection

For Diode Selection, both forward voltage drop and diode

capacitance need to be considered. Shottky diodes with higher

current ratings usually have lower forward voltage and larger diode

capacitance, which can cause significant switching losses. A

schottky diode rated at 100

to 200

is sufficient for most

KIB3402F applications.

Table 1. Recommended Schottky Diodes

LED Current Control

Figure 1). The feedback reference is 320

.

The LED current is 320

Open-Circuits Protection

In the case of output open circuit, when LEDs are disconnected

from the circuit or the LEDs fail, the feedback voltage will be zero.

The KIB3402F will then switch at a high duty cycle resulting in a

high output voltage, but Internal Over Voltage Protection Circuits

prevent output voltage ascending over OVD pin voltage( 16V ~ 22V

see Fig.4 ). This circuits is valid when driving up to 4 LEDs in

series. But, when driving more than 4 LEDs in series, Normal

output voltage could be over OVD pin voltage.

In this case, zener diode can be used to limit output voltage, but

check connection of OVD pin to VCC.(see Fig.5)

LOAD CURRENT (mA)

10

70.00

72.00

74.00

76.00

78.00

80.00

82.00

84.00

86.00

88.00

90.00

05

20

15

25

4.7uH

Vin=3.6V, 4LED

Inductor=Murata

10uH

Figure3. Efficiency Comaprison of different value inductors

Figure4. 4LEDs driver with Open-circuit protection.

Figure5. 6LEDs driver with Open-circuit protection.

0

GND

SW

L1

C1

C2

KIB3402F

D1

CTL

FB

OVD

LED1

LED2

LED3

LED4

0

GND

SW

L1

C1

C2

16

Ω

R1

KIB3402F

D1

CTL

FB

LED1

LED2

LED5

LED6

LED3

LED4

OVD

1

2

4

3

6

5

1

2

4

3

6

5

1 F

µ

4.7 H~10 H

µ

µ

4.7 H~10 H

µ

µ

1 F

µ

1 F

µ

1 F

µ

Dimming Control

There are 4 different type of dimming control circuits:

1. Using a DC Voltage to CTL pin.

Description

UNIT

0V~0.5V

Rate Of the LED Current

0

25 ~ 100

100

%

0

5 ~ 20

20

mA

Part No.

Reverse

Voltage (V)

Forward

Current (mA)

Voltage

Drop (V)

Package

KDR730E

30

200 mA

0.6V (max)

at 200 mA

1.60

1.20

KDR720E

30

200 mA

0.5V(max)

at 200 mA

1.60

1.20

KDR412

20

500 mA

0.5V(max)

at 500 mA

1.70

2.50