KDR730E View Datasheet(PDF) - KEC
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KAB3403T/DN
Inductor Section
A 10uH inductor is sufficient for most application. The efficiency
comparision of different value inductors help you design your
application circuits.
90
88 VIN=3.6, 4LED Inductor=Murata
86
84
82
80
78
76
74
72
70
68
66
64
10µH
62
4.7µH
60
0
5 10 15 20 25 30 35
LOAD CURRENT (mA)
Figure3. Efficiency Comparison of different value inductors
Inductor Section
A 1uF input capacitor and output capacitor above 1uF are
sufficient for most KAB3403T/DN application.
Diode Selection
For Diode Selection, both forward voltage drop and diode
capacitance need to be considered. Schottky 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 100mA to 200mA is sufficient for most
KAB3403T/DN applications.
Part No. Reverse
Forward
Voltage
Voltage (V) Current (mA) Drop (V)
KDR730E
30
0.6V (max)
200 mA at 200 mA
Package
1.60
1.20
KDR720E
30
0.5V(max)
1.60
1.20
200 mA
at 200 mA
KDR412
20
0.5V(max)
500 mA
2.50
1.70
at 500 mA
Table1. Recommended Schottky Diode
LED Current Control
The LED current is controlled by the feedback resistor (RSENSE
in Figure 1). The feedback reference is 320mV. The LED current
is 320mV/RSENSE . The tolerance of LED Current is depends on
tolerance of RSENSE and feedback reference.
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 KAB3403T/DN 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(19V ~ 23V 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 check connect of OVD pin to
LED anode.(see Fig 5) [Recommended Zener diode : KDZ3.0V]
L1
4.7µH ~ 22µH D1
VIN
LED1
VCC
SW
OVD
LED2
LED3
KAB3403T/DN
C2
1µF
LED4
CTL
FB
GND
C1
1µF
R1
16Ω
Figure4. 4LEDs driver with Open-circuit protection.
L1
4.7µH~22µH
D1
VIN
LED1
VCC
SW
LED2
OVD
LED3
KAB3403T/DN
LED4
C2
1µF
LED5
CTL
LED6
GND
FB
C1
1µF
R1
16Ω
Figure5. 6LEDs driver with Open-circuit protection.
Dimming Control
There are 4 different type of dimming control circuits;
1. Using a DC Voltage to CTL pin
Description
VCTL
UNIT
0V~0.5V 1V~2.5V VCTL>2.5V
Rate Of the LED Current 0 25 ~ 100 100
%
Example : RSENSE = 16
0
5 ~ 20
20
mA
Table 2 CTL pin Voltage vs ILED
2007. 2. 26
Revision No : 0
4/7
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