SEMICONDUCTOR KAB3405T TECHNICAL DATA BICD LINEAR INTEGRATED CIRCUIT 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. E K 6 2 5 3 4 DIM A B C D E F 1 G B G A K D Features Variable LED Current IF is set with a external resistor C High Efficiency L : 20 mA (Typ.) @ RSENS = 15 Output Over Voltage Shutdown I Built in output over voltage protect circuit. J F G MILLIMETERS _ 0.2 2.9 + 1.6+0.2/-0.1 _ 0.05 0.70 + _ 0.1 0.4 + 2.8+0.2/-0.3 _ 0.2 1.9 + 0.95 H I _ 0.05 0.16 + 0.00-0.10 J 0.25+0.25/-0.15 K L 0.60 0.55 H J Switching Frequency : 1.0 MHz (Typ.) Applications Back light white LEDs in LCD of PDA, Cellular Phone Handy Terminal Equipment. TS6 Basic Application Circuit 2007. 4. 2 Revision No : 0 1/7 KAB3405T Block Diagram Pin Function Pin No. Symbol 1 SHDN 2 OVD 3 VIN Supply Voltage Input Terminal. ( 2.8V to 5.5V) 4 SW Switch Terminal for DC/DC Converter. Nch MOSFET Built-In. 5 GND 6 FB 2007. 4. 2 Function Description Voltage-Input Terminal for IC-Enable / Disable LED-IF. IF adjustment with PWM input signal is also available. 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. Ground Terminal. LED IF Setting Resister Connecting Terminal. Revision No : 0 2/7 KAB3405T AUTE MAXIMUM RATINGS (Ta = 25 C if without notice) Characteristics Symbol Ratings Unit VIN -0.3 to +6.0 V VIN(SHDN) -0.3 to +VIN + 0.3 V Switching Terminal Voltage VO (SW) -0.3 to 40 V Switching Terminal Current IO (SW) 1500 mA Power Supply Voltage Input Voltage 0.41 (Device) PD Power Dissipation W 0.47(on PCB)Caution 2 300(Device) Rth(j-a) Thermal Resistance /W 260(on PCB) Operation Temperature Range Topr -40 to +85 Storage Temperature Range Tstg -55 to +150 Tj 150 Maximum Junction Temperature 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 Characteristics Input Voltage Range , VIN=2.8V to 5.5V if without notice) Symbol Test Condition Min Typ Max Unit VIN - 2.8 - 5.5 V mA Operating Consumption Current IN(ON) VIN=3.6V, RSENS=15 - 0.6 0.9 Quiescent Consumption Current IN(Off) VIN=3.6V,VSHDN=0V - 0.5 1.0 VSHDNH - 1.3 - VIN V SHDN Terminal ’L’ Level Input Voltage VSHDNL - 0 - 0.4 V - 0 1.0 0.77 1.0 1.43 - 0.5 1 VIN=3.6V, RSENS=15 , Ta=25 C, L=22 H 285 300 315 mV VIN=3.6V, RSENS=15 , Ta=25 C, L=22 H 285 300 315 mV % SHDNTerminal ’H’ Level Input Voltage SHDN Terminal Current ISHDN VIN=3.6V,VSHDN=3.6V or 0V Integrated MOS-Tr Switching requency fOSC VIN=3.6V,VSHDN=3.6V Switching Terminal Leak Current FB Terminal Feedback Voltage (VFB) IOZ(SW) VFB - FB Terminal Line Regulation VFB VIN=3.6V center VIN=3.0 to 5.0V -5 - 5 FB Terminal Current IFB VIN=3.6V, VSHDN=3.6V, VFB=300mV - 0.02 - 36 38 39.5 - 0.5 1 OVD terminal Voltage VOVD OVD Terminal Leakage Current IOVD 2007. 4. 2 Revision No : 0 VOVD=30V MHz V 3/7 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 CIN = Over 2.2 ( F), COUT = Over 1.0 ( F) In case with PWM signal to SHDN terminal for brightness control, recommended values are CIN = Over 4.7 ( F), COUT=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 IF = 20 mA LEDs Indictor Size Note 2-5 Over 6 10 H 22 H LED current IF = 20 mA Setting of IF 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] = Current Value error is within 2007. 4. 2 300[mV] RSENS[ ] 5%. Revision No : 0 4/7 KAB3405T Current Dimming Control Recommended Brightness Control Circuits are 4 types. 1) Input PWM signal to SHDN terminal IF can be adjusted with PWM signal by inputting it to SHDN terminal. [Notice] <<PWM signal frequency>> The recommended PWM signal frequency is from 100 Hz to 10 kHz. There is a possibility to arise the audible frequency in mounting to the board because it is within the auditory area. <<Constant number of external condenser>> To reduce the fluctuation of input current and increase the accuracy of brightness, the values that CIN = 4.7 ( F) or more , COUT = 1.0 ( F) or less are recommended. When the PWM signal is off, the time to drain COUT of charge depends on the constant number. And so, the actual value is little different from the theoretical value. <<PWM input signal>> Set the amplitude of PWM signal within the range of SHDN terminal specification. <<Rush current in inputting>> In case dimming by inputting the PWM signal to the SHDN terminal, this IC turns on and off repeatedly. And the rush current, which provides the charge to COUT, arises in turning on. Take care in selecting the condenser. <<Current value in Control with PWM: Ideal Equation>> IF [mA] = 300 [mV] ON Duty [%] RSENS[ ] <<Recommended application>> 2007. 4. 2 Revision No : 0 5/7 KAB3405T 2) 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) <<Recommended application>> 3) 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). <<Recommended application>> 2007. 4. 2 Revision No : 0 6/7 KAB3405T 4) 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 [ ] <<Recommended application>> M1 M2 LED Current OFF OFF 300[mV] RSENS[ ] ON OFF 300[mV] RSENS[ ] R1[ ] RSENS[ ]+ R1[ ] OFF ON 300[mV] RSENS[ ] R2[ ] RSENS[ ]+ R2[ ] ON ON 2007. 4. 2 300[mV] Revision No : 0 RSENS[ RSENS[ ] R1[ ] R2[ ] ] R1[ ] + RSENS[ ] R2[ ] + R1[ ] R2[ ] 7/7