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| SEMICONDUCTOR TECHNICAL DATA Step Up Type DC/DC Converter for White LED KAB3405T is a high efficient Step-Up Type DC/DC Converter specially designed for constant current drive of White LED. This IC can drive 2-10 white LEDs connected series using a Li-ion Battery. This IC contains N-ch MOS-FET Transistor for Coil-Switching, and LED Current (IF) is set with an external resistor. KAB3405T BICD LINEAR INTEGRATED CIRCUIT Features Variable LED Current IF is set with a external resistor : 20 mA (Typ.) @ RSENS = 15 High Efficiency Output Over Voltage Shutdown Built in output over voltage protect circuit. Switching Frequency : 1.0 MHz (Typ.) Applications Back light white LEDs in LCD of PDA, Cellular Phone Handy Terminal Equipment. Basic Application Circuit 2008. 3. 10 Revision No : 2 1/6 KAB3405T Block Diagram Pin Function Pin No. 1 2 3 4 5 6 Symbol SHDN OVD VIN SW GND FB Voltage-Input Terminal for IC-Enable / Disable. Over Voltage Detection Terminal. IC Switching Operation is disabled with detection over voltage. If the voltage returns to detection level or less, Operation is enabled again. Supply Voltage Input Terminal. ( 2.8V to 5.5V) Switch Terminal for DC/DC Converter. Nch MOSFET Built-In. Ground Terminal. LED IF Setting Resister Connecting Terminal. Function Description 2008. 3. 10 Revision No : 2 2/6 KAB3405T MAXIMUM RATINGS (Ta = 25 C if without notice) Characteristics Power Supply Voltage Input Voltage Switching Terminal Voltage Switching Terminal Current Power Dissipation Symbol VIN VIN(SHDN) VO (SW) IO (SW) PD 0.47(on PCB)Caution 2 300(Device) Thermal Resistance Operation Temperature Range Storage Temperature Range Maximum Junction Temperature Rth(j-a) 260(on PCB) Topr Tstg Tj -40 to +85 -55 to +150 150 /W Ratings -0.3 to +6.0 -0.3 to +VIN + 0.3 -0.3 to 40 1500 0.41 (Device) W Unit V V V mA Caution 2: Power Dissipation must be calculated with subtraction of 3.8 mW/ C from Maximum Rating with every 1 if Topr is upper 25 C. (on PCB) ELECTRICAL CHARACTERISTICS (Ta = 25 , VIN=2.8V to 5.5V if without notice) Characteristics Input Voltage Range Operating Consumption Current Quiescent Consumption Current SHDNTerminal 'H' Level Input Voltage Symbol VIN IN(ON) IN(Off) VSHDNH VIN=3.6V, RSENS=15 VIN=3.6V,VSHDN=0V VIN=3.6V,VSHDN=3.6V or 0V VIN=3.6V,VSHDN=3.6V VIN=3.6V, RSENS=15 , Ta=25 C, L=22 H VIN=4.2V, RSENS=15 , Ta=25 C, L=22 H FB Terminal Line Regulation FB Terminal Current OVD terminal Voltage OVD Terminal Leakage Current VFB IFB VOVD IOVD VOVD=30V VIN=3.6V center VIN=3.0 to 5.0V VIN=3.6V, VSHDN=3.6V, VFB=300mV Test Condition Min 2.8 1.3 0 0.77 285 285 -5 35 Typ 0.6 0.5 0 1.0 0.5 300 300 0.02 38 0.5 Max 5.5 0.9 1.0 VIN 0.4 1.0 1.43 1 315 315 5 39.5 1 V mV mV % MHz V V Unit V mA SHDN Terminal 'L' Level Input Voltage VSHDNL SHDN Terminal Current Integrated MOS-Tr Switching requency Switching Terminal Leak Current FB Terminal Feedback Voltage (VFB) ISHDN fOSC IOZ(SW) VFB 2008. 3. 10 Revision No : 2 3/6 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 recommended values are CIN = Over 2.2 ( F), COUT = Over 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. 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 IF = 20 mA LEDs 2-5 Over 6 Setting of IF Inductor Size 10 H 22 H Note LED current IF = 20 mA Resistance connects between RSENS pin and GND. The average current is set by this RSENS value and average current are obtained by the following equation. IF[mA] = 300[mV] RSENS[ ] Current Value error is within 5%. 2008. 3. 10 Revision No : 2 4/6 KAB3405T Current Dimming Control Recommended Brightness Control Circuits are 3 types. 1) Input analog voltage to FB terminal IF can be adjusted with Analog voltage input to FB terminal. This method is without repeating IC ON/OFF, and no consider holding rash current. [Notice] LED current value goes ever 100% of current set with RSENS, if the input voltage is between 0 V to 300 mV(typ) < 2) Input PWM signal with filtering to FB terminal IF can be adjusted with filtering PWM signal using RC filter indicated in recommended circuit, because the PWM signal can be regard as analog voltage after filtering. This method is without repeating IC ON/OFF, and no need to consider holding rash current. [Notice] LED current value goes over 100% of the current set with RSENS, if the input voltage after filtering is between 0 V to 300 mV (typ). < 2008. 3. 10 Revision No : 2 5/6 KAB3405T 3) Input Logic signal IF can be adjusted with Logic signal input as indicated in recommended circuit. The resistor connected the ON-state Nch MOS Drain and RSENS determines IF. Average of setting current Io (mA) is next, approximately. IF=(300 [mV]/Sum of resistor value [ ]) IF [mA] = 300[mV] Sum of resistor v alue [ ] < M1 OFF ON OFF ON M2 OFF OFF ON ON 300[mV] 300[mV] 300[mV] LED Current 300[mV] RSENS[ ] RSENS[ ] R1[ ] RSENS[ ]+ R1[ ] RSENS[ ] R2[ ] RSENS[ ]+ R2[ ] ] RSENS[ RSENS[ ] R1[ ] R2[ ] ] R1[ ] + RSENS[ ] R2[ ] + R1[ ] R2[ 2008. 3. 10 Revision No : 2 6/6 |
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