KAB3405T Datasheet, PDF (4/7 Pages) KEC(Korea Electronics) – Step Up Type DC/DC Converter for White LED

KAB3405T
Protection in LED opened condition
The operation with OVD terminal is available for the protection in case LED Circuit opened.
When the voltage of OVD terminal is over 38V (typ.), Nch MOS switching operation is disabled in the IC. When the voltage of
OVD terminal drops below 38V (typ.), Nch MOS switching operation becomes available again.
If load of LED is detached, Nch MOS switching operation is disabled with detection of boost circuit voltage and the IC is
protected from unexpected over voltage.
Setting of external Capacitor
In case not using PWM signal to SHDN terminal for brightness control, recommended values are
C_IN = Over 2.2 ( F), C_OUT = Over 1.0 ( F)
In case with PWM signal to SHDN terminal for brightness control, recommended values are
C_IN = Over 4.7 ( F), C_OUT=Under 1.0 ( F)
The recommended values of the capacitors depend on the control of brightness. For details, please see the item Control of
brightness from the next page.)
These recommended values reduce fluctuation of input current to up accuracy of brightness.
<Please see after page-6>
The capacitor value must be considered for gain enough accuracy of brightness with reduction of noise from
Input current changing.
Setting of External Inductor Size
Please select the inductor size with referring this table corresponding to each number of LEDs.
Recommendation for the case that LED current I_F = 20 mA
LEDs
2-5
Over 6
Indictor Size
10 H
22 H
Note
LED current I_F = 20 mA
Setting of I_F
Resistance connects between R_SENS pin and GND.
The average current is set by this R_SENS value and average current are obtained by the following equation.
I_F[mA] =
300[mV]
R_SENS[ ]
Current Value error is within 5%.
2007. 4. 2
Revision No : 0
4/7