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| Kingbor Technology Co.,Ltd TEL:(86)0755-26508846 FAX:(86)0755-26509052 KB4317 High Efficiency, Constant Current 2 Watt Boost White-LED Driver FEATURES *Operating Voltage:2.3V~6.5V *High Operating Frequency: 1.2MHz *High Efficiency: Up to 90% *High Output Voltage: Up to 32V *High Output Power: 2W *Shutdown Current <1 A *30V Output Over-voltage protection (min) *Digital Dimming Control. *Built-in Cycle-by Cycle Current-limiting. *Built-in Soft-Start Function. *0.25V Low Reference Voltage(+/-5%) *Tiny SOT23-6 Package DESCRIPTION The KB4317 step-up converter drives white LEDs with a constant current to provide backlight in cell phones, PDAs, and other hand-held devices. It features allowing series connection of the white LEDs so that the LED currents are identical for uniform brightness. An enable input can be pulsed repeatedly to adjust LED's brightness. The fast 1.2 MHz current-mode PWM control allows for smaller capacitor and inductor. Fault condition protection uses cycle-by-cycle current limiting to sense maximum inductor current, thermal protection and over-voltage protection. Also included soft-start eliminates inrush current during start-up. The 0.25V low reference voltage minimized the power loss across the current-setting resistor. The KB4317 is available in SOT23-6 packages APPLICATIONS * LED Module * LED Backlight for LCD Display Vcc>3.6V(7 "~8 ") * Constant Current Source SIMPLIFIED BLOC DIAGRAM VIN LX ON/OFF Control Logic / PWM Dimming Control VREF(250mV) + Control Logic FB OVP 22V(300uA) VBG + Overvoltage Protection Current Limit 0.75A + CTL N VREF 0.25V VBG 1.23V Soft-Start EN CTL GND REV: 1.0 1 Kingbor Technology Co.,Ltd TEL:(86)0755-26508846 FAX:(86)0755-26509052 KB4317 High Efficiency, Constant Current 2 Watt Boost White-LED Driver PIN CONFIGURATION SOT23-6 Marking ORDER INFORMATION Part number Package Marking KB3417GRE SOT23-6,Pb Free ZL54, Date Code with one bottom line PIN DESCRIPTION Pin N0. 1 2 3 4 5 6 Symbol LX GND FB EN OVP VIN I/O I P I I I P Description Step-up Regulator N-MOS Drain. Place output diode and inductor. Ground Step-Up Regulator Feedback Input. Connect a sense resistor from FB to ground. Enable and Dimming Control Input. LED brightness and IC shutdown are controlled by the voltage on EN. Driving low for longer than 4ms to shutdown the IC. Over-voltage protection input. Connect to the output. Power supply. ABSOLUTE MAXIMUM RATINGS (Note 1) Parameter VIN voltage LX , OVP voltage EN , FB to GND Switch Current (ILX) Continuous power dissipation (SOT23-6 Ta=+25 OC) Operating Junction Temperature Range Lead Temperature (Soldering 5 sec) Storage Temperature Package Thermal Resistance ( JA) ESD Susceptibility (HBM) ESD Susceptibility (MM) Rated Value -0.3 to +6.5 -0.3 to +34 -0.3 to +6.5 0.75 0.35 -35 to 85 260 -65 to 125 250 2 200 Unit V V V A W /W KV V Note1:Permanent device damage may occur if Absolute Maximum Ratings are exceeded. Exposure to absolute maximum rating conditions for extended periods may affect device reliability REV: 1.0 2 Kingbor Technology Co.,Ltd TEL:(86)0755-26508846 FAX:(86)0755-26509052 KB4317 High Efficiency, Constant Current 2 Watt Boost White-LED Driver RECOMMENDED OPERATION CONDITIONS Parameter Power supply voltage Operating temperature Symbol VIN Top Min. 2.3 -30 Values Typ. +25 Max. 6.5 +85 Unit V ELECTRICAL CHARACTERISTICS (VIN=2.5V, Ta=+25 , unless otherwise noted) Parameter Operating V IN Range Under Voltage Thershold Switch- Off Input Current Shutdown Current Feedback Reference (+/-5%) FB Input Bias Current Over-voltage Threshold Over-voltage Hysteresis OVP Leakage Current Output Voltage Line Regulation Switching Frequency Maximum Duty Soft-Start charging time Switching Current Limit LX ON Resistance LX Leakage Current EN Input Current EN Input Level EN low Shutdown Delay EN Low Cycle Time EN High Cycle Time Symbol Test Condition VIN input Voltage VIN UVLO IIN1 IIN3 V FB IFB VOVP IOVP fOSC DMAX tSS ILX RLX ILeakage IEN VIH VIL tCYCL tCYCH VIN falling, 100mV hysteresis No Switching , FB>0.3V EN=0V VFB =0.105V VOUT Rising EN=0V 2.5V< VIN <6.0V Min. 2.3 Typ. Max. Units 6.5 V V uA uA V uA V V uA % MHz % ms A uA uA V V ms ms ms 1.4 1.5 1.6 100 350 1 0.238 0.25 0.262 1 17 22 25 5 1 1.0 0.05 1.5 0.05 0.05 0.1 1.2 90 0.2 0.75 0.40 4 1.4 1 1 0.4 4 4 VIN=3.0V,duty cycle=80% , VIN =2.5V, ILX =750mA VLX =16V, EN=0V EN=5V Note(1) Note(1) Note(1): tCYCL and tCYCH are included rising time and falling time of PWM signal. Recommended PCB Layout REV: 1.0 3 Kingbor Technology Co.,Ltd TEL:(86)0755-26508846 FAX:(86)0755-26509052 KB4317 High Efficiency, Constant Current 2 Watt Boost White-LED Driver TYPICAL PERFORMANCE CHARACTERISTICS 1. Driving Capability Vin 2.4V 3.6V 5.0V ILED=12.5mA 6 x 1LED 3 x 9LED 3 x 10LED ILED=20mA 4 x 1LED 3 x 6LED 3 x 10LED 2.Efficiency Figure 3. Efficiency vs Vin and ILED Figure 4. Efficiency vs Temperature 3. Quiescent Current vs VIN and Temperature Figure 5. Iq vs. Temperature 4.Switching Frequency vs Temperature Figure 6. Fosc vs. Temperature REV: 1.0 4 Kingbor Technology Co.,Ltd TEL:(86)0755-26508846 FAX:(86)0755-26509052 KB4317 High Efficiency, Constant Current 2 Watt Boost White-LED Driver APPLICATION CIRCUIT VIN1 2.4V to 6V 4.7uF 10uH 1N5819 LX 1uF R=(VF-22V)/300uA if VF=30V,R=27K VIN2 2.4V to 6.0V 1uF ON OFF PWM Signal VIN OVP 8LEDs KB4317 EN GND FB I LED 250mV RSENSE 13.8 Figure 1a. KB4317 Typical Application Circuit with 18mA 8LEDs Output . up to 30 LEDs 10uH VIN 3.6V to 6.0V 4.7uF 1N5817 LED1 10uF LED30 VIN LX OVP X10 ON OFF PWM Signal KB4317 EN GND FB I LED 250mV RSENSE 2.2 Figure 1b. KB4317 for 8 " Panel LED Back light unit . (10V 113mA) REV: 1.0 5 Kingbor Technology Co.,Ltd TEL:(86)0755-26508846 FAX:(86)0755-26509052 KB4317 High Efficiency, Constant Current 2 Watt Boost White-LED Driver Function Description The KB4317 is a high efficiency and constant current DC-DC converter IC which is designed primarily for use in LED module applications. The output voltage of the step-up converter can be set from Vin to 30V with external sense resistor. The device suits to drive series-connected LEDs and provides even illumination by sourcing the same output current through each LED. KB4317 also consists of a logic shutdown , cycle-by-cycle current-limited , soft-start functions. Logic control input or PWM duty cycle control allows easy adjustment of LEDs brightness and on/off control. The average LED current is proportionable the duty-cycle of the PWM signal. Typical PWM frequency should be between 100Hz and 1kHz. The boost converter operates in current-mode PWM and a constant frequency of 1.2 MHz. Depending on duty cycle of each switching cycle can regulate output voltage. On the rising edge of the internal clock , the control and driver logic block sets internal flip-flop when the output voltage is too low, which turns on the N-MOS. The external inductor current ramps up linearly, storing energy in a magnetic filed. Once peak current of inductor over trans-conductance output level , the N-MOS turns off, the flip-flop resets, and external schottky diode turns on. This forces the current through the inductor to ramp back down, transferring the energy stored in the magnetic field to the output capacitor and LEDs. To reduce external component amount , the device will be built-in internal loop compensation. Enable Control Digital logic of EN provides an electrical ON/OFF control of the power supply. Connecting this pin to ground or to any voltage less than 0.4V and sustain the level over 4ms will completely turn off the regulator. In this state, current drain from the input supply is less than 1uA, the internal reference, error amplifier, comparators, and biasing circuitry turn off . If holding time of low level is less than 3ms on this pin, then the device only shutdown driver logic block. Dimming Control Digital logic of EN also provides LEDs brightness control by applying a PWM signal on EN pin. With this way, the LEDs operate with either zero or full current . The average LED current is proportional to the duty-cycle of the PWM signal. Typical PWM frequency should be between 100Hz and 1kHz. Output current is given by: I LED Where: 250mV TON PWM RSENSE TS PWM TON-PWM : On time of PWM signal TS-PWM : A cycle time of PWM signal If dimming control is not required , EN works as a simple on/off control. Drive EN high to enable the device , or drive EN low for shutdown. REV: 1.0 6 Kingbor Technology Co.,Ltd TEL:(86)0755-26508846 FAX:(86)0755-26509052 KB4317 High Efficiency, Constant Current 2 Watt Boost White-LED Driver Soft-Start Soft-start allows a gradual increase of the internal current-limit level for the step-up converter during power-up to reduce input surge currents. As the internal current source charges the internal soft-start capacitor, the peak N-MOS current is limited by the voltage on the capacitor. In another story, when toggle or a logic-level transition on EN pin from low to high, soft-start function must work to enable constant current charging internal capacitor. When soft-start process has finished or appeared falling edge of PWM signal on EN pin , soft-start capacitor must be discharged to ground level. Cycle-by-Cycle Over-Current Protection The KB4317 provides cycle-by-cycle over-current protection. Current limit is accomplished using a separate dedicated comparator. The cycle-by-cycle current limit abbreviates the on-time of the N-MOS in event that the current of flowing N-MOS is greater than the current limit value. The current-limit feature protection against a hard short or over-current fault at the output. Over-Voltage Protection If VOUT is above 22V or LEDs are disconnected from the circuit, the FB pin is similar to pull down to ground with a sense resistor. This will cause N-MOS to switch with a maximum duty cycle and come out output over-voltage. This may cause the LX pin voltage to exceed its maximum voltage rating to damage built-in N-MOS. In the state, the OVLO protection circuitry stops the internal N-MOS . When VOUT falls below 22V, IC will automatically recover normal operation. Power dissipation consideration The KB4317 maximum power dissipation depends on the thermal resistance of the IC package and circuit board, the temperature difference between the die junction and ambient air, and the rate of any airflow. The power dissipation in the device depends on the operating conditions of the regulator. The step-up converter dissipates power across the internal N-MOS as the controller ramps up the inductor current. In continuous condition, the power dissipated internally can be approximated by : Pboost where [( I O VO 2 ) Vin 1 Vin D 2 ( ) ] RDS (ON ) 12 f OSC L D IO : It is the load current. fOSC : It is a switching frequency. REV: 1.0 7 Kingbor Technology Co.,Ltd TEL:(86)0755-26508846 FAX:(86)0755-26509052 KB4317 High Efficiency, Constant Current 2 Watt Boost White-LED Driver Applications Information External components of main boost converter can be designed by performing simple calculations. It need to follow regulation by the output voltage and the maximum load current, as well as maximum and minimum input voltages. Begin by selecting an inductor value. Once L is know, choose the diode and capacitors. Boost inductor Inductor selection depends on input voltage, output voltage, maximum current , switching frequency and availability of inductor values. The following boost circuit equations are useful in choosing the inductor values based on the application. They allow the trading of peak current and inductor value while allowing for consideration of component availability and cost. The peak inductor current is given by: I Lpeak I LAVG where: I LAVG IO 1D IL 2 IL is the inductor peak-to-peak current ripple and is decided by: IL Vin L VO V in VO D f OSC D is the MOSFET turn on ratio and is decided by: D fOSC is the switching frequency. The inductor should be chosen to be able to handle this current and inductor saturation current rating should be greater than IPEAK. Diode selection The output diode has average current of IO, and peak current the same as the inductor's peak current and a voltage rating at least 1.5 times the output voltage. Schottky diode is recommended and it should be able to handle those current. Output Capacitor The KB4317 is specially compensated to be stable with capacitors which have a worst- case minimum value of 1uF at the particular VOUT being set. Output ripple voltage requirements also determine the minimum value and type of capacitors. Output ripple voltage consists of two components the voltage drop caused by the switching current through the ESR of the output capacitor and the charging and discharging of the output capacitor: V RIPPLE I LPEAK ESR VO Vin VO IO C OUT f OSC For low ESR ceramic capacitors, the output ripple is dominated by the charging or discharging of the output capacitor. REV: 1.0 8 Kingbor Technology Co.,Ltd TEL:(86)0755-26508846 FAX:(86)0755-26509052 KB4317 High Efficiency, Constant Current 2 Watt Boost White-LED Driver PACAGE DESCRIPTION Small Outline SOT23-6 b e E e1 D A A2 A1 C r E1 L SYMBOL A A1 A2 b C D E E1 L e e1 r INCHES MIN 0.035 0.000 0.035 0.010 0.003 0.110 0.102 0.059 0.014 0.037ref 0.075ref 00 100 MAX 0.057 0.006 0.051 0.020 0.008 0.122 0.118 0.069 0.022 MILLIMETERS MIN MAX 0.90 1.45 0.00 0.15 0.90 1.30 0.25 0.50 0.08 0.20 2.80 3.10 2.60 3.00 1.50 1.75 0.35 0.55 0.95ref 1.90ref 00 100 NOTES - - Kingbor Technology TEL:(86)0755-26508846 FAX:(86)0755-26509052 www.kingbor.com 9 |
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