UNISONIC TECHNOLOGIES CO., LTD L5101 LINEAR INTEGRATED CIRCUIT WHITE LED STEP-UP CONVERTER DESCRIPTION The UTC L5101 is a constant current step-up PWM DC/DC converter optimized to drive white LEDs. It can drive LEDs in series with a Li-Ion cell. The switching frequency of the internal NPN is up to 1.2MHz. High frequency allows the use of tiny external components and the current setting resistor has minimum power dissipation for the low feedback voltage of 95mV. The built-in OVP prevents the UTC L5101 damage from the open load condition. Series connection of LEDs provides identical LED currents which contributes to uniform brightness, saving the use of ballast resistors. The UTC L5101 is universally used in cellular phones, PDAs , DSCs, handheld devices, and white LED display backlighting. 6 5 4 1 2 3 SOT-26 FEATURES * Open Circuit and Over Voltage Protection * High Efficiency: 86% Typical * Switching Frequency: 1.2MHz * Supply Current is 1.0mA * Matches LED Current * Requires Tiny Inductor and Capacitors * Halogen Free ORDERING INFORMATION Ordering Number L5101G-AG6-R Package SOT-26 Packing Tape Reel MARKING www.unisonic.com.tw Copyright © 2009 Unisonic Technologies Co., Ltd 1 of 10 QW-R103-026.B L5101 LINEAR INTEGRATED CIRCUIT PIN CONFIGURATION PIN DESCRIPTION PIN NO. 1 2 3 4 5 6 PIN NAME Shutdown Ground SYMBOL DESCRIPTION SHDN Tie to higher than 1.5V to enable device, 0.3V or less to disable device. GND Reference voltage is 95mV. Connect cathode of lowest LED and Feedback FB resistor here. Calculation formula: RFB=95mV/ILED Connect inductor/diode here. Minimize trace area at this pin to reduce Switch SW EMI. Power input VIN Bypass VIN to GND with a capacitor sitting as close to VIN as possible. Over voltage protection OVP The internal NPN will turn off when VOUT >27V. UNISONIC TECHNOLOGIES CO., LTD www.unisonic.com.tw 2 of 10 QW-R103-026.B L5101 LINEAR INTEGRATED CIRCUIT BLOCK DIAGRAM VIN 5 95mV Over Voltage Comparator 1.25V VREF + 27V - PWM Comparator - Control Logic Driver 6 OVP 4 SW 2 GND Q1 + + M FB 3 Error AMP RC RAMP GENERATOR CC SHDN 1 + Current AMP. UNISONIC TECHNOLOGIES CO., LTD www.unisonic.com.tw 1.2MHz Oscillator - RS 3 of 10 QW-R103-026.B L5101 LINEAR INTEGRATED CIRCUIT ABSOLUTE MAXIMUM RATING PARAMETER SYMBOL RATINGS UNIT Input Voltage VIN 6 V SW Voltage VSW 33 V FB Voltage VFB 6 V SHDN Voltage VSHDN 6 V OVP Voltage VOVP 34 V Junction Temperature TJ +125 ℃ Operating Temperature Range TOPR -20 ~ +85 ℃ Storage Temperature Range TSTG -40 ~ +150 ℃ Note: Absolute maximum ratings are those values beyond which the device could be permanently damaged. Absolute maximum ratings are stress ratings only and functional device operation is not implied. ELECTRICAL CHARACTERISTICS (VSHDN=3V, VIN=3V, Ta=25℃, unless otherwise specified.) PARAMETER Operating Voltage Supply Current ERROR AMPLIFIER Feedback Voltage FB Input Bias Current OSCILLATOR Switching Frequency Maximum Duty Cycle POWER SWITCH SW ON Resistance Switch Leakage Current CONTROL INPUT High Low OVER VOLTAGE PROTECTION OVP Input Resistance OVP Threshold Shutdown Voltage SYMBOL VIN IIN VFB IFB TEST CONDITIONS Switching Non switching VSHDN=0V fSW DC RIN(OVP) VTHR(OVP) 1V Hysteresis typical UNIT V mA μA 95 100 105 mV nA 0.8 85 1.2 90 1.6 MHz % 1.4 0.1 5 1 Ω μA 0.3 V V 1.8 32 MΩ V ILEAK (SW)) VSW=33V ON OFF MAX 5.5 5 2 1.0 85 RON(SW) VIH(SHDN) VIL(SHDN) TYP 2 1 0.1 VFB=95mV UNISONIC TECHNOLOGIES CO., LTD www.unisonic.com.tw MIN 2.5 1.5 0.6 22 1.2 27 4 of 10 QW-R103-026.B L5101 LINEAR INTEGRATED CIRCUIT TEST CIRCUIT Fig.1 Test Circuit UNISONIC TECHNOLOGIES CO., LTD www.unisonic.com.tw 5 of 10 QW-R103-026.B L5101 LINEAR INTEGRATED CIRCUIT APPLICATION INFORMATION Recommended Component Selection * Inductor Selection: A 10μH inductor is recommended for most applications. * Capacitor Selection: The small size of ceramic capacitor makes it ideal for UTC L5101 applications, X5R and X7R types are recommended because of their stable characteristics, 1μF input capacitor with 1μF output capacitor is sufficient for most UTC L5101 applications. * Diode Selection: Schottky diode, for its low forward voltage drop and fast reverse recovery, is an ideal choice for the UTC L5101 diode. A Schottky diode rated 100mA to 200mA is sufficient for most UTC L5101 applications, and the higher current rating usually have larger diode capacitance which can cause significant switching losses at the 1.2MHz switching frequency. LED Current Control A feedback resistor (precision 1% recommended) as feedback resistor control the LED current. (RFB in Figure 1) * Feedback reference voltage: 95mV. * LED current is 95mV/RFB. * The formula for RFB selection: RFB=95mV/ILED Open-Circuit Protection The OVP(Over Voltage Protection) protects the voltage lower than its maximum level under the open circuit condition, which is caused by the failure or disconnection of the LEDs. The above undesired fault conditions will cause the feedback voltage falling to 0V, then the UTC L5101 increases duty circle resulting in a high voltage in SW pin. Dimming Control There are three different ways of dimming control circuits as follows: 1. Using a PWM signal L1 10µH D1 VIN VIN SW OVP C2 1µF UTC L5101 C1 1µF SHDN GND PWM FB R2 R1 51K 1K RFB 4.7Ω Fig. 2 Dimming Control Using a PWM Signal Fig. 3 Dimming Control with a PWM Signal UNISONIC TECHNOLOGIES CO., LTD www.unisonic.com.tw 6 of 10 QW-R103-026.B L5101 LINEAR INTEGRATED CIRCUIT APPLICATION INFORMATION(Cont.) 2. Using a DC Voltage L1 10µH D1 VIN VIN OVP SW C2 1µF UTC L5101 C1 1µF SHDN FB GND VDC 0~5V R2 R1 51K 1K RFB 4.7Ω Fig. 4 Dimming Control Using a DC Voltage 3. Using a Filtered PWM Signal L1 10µH D1 VIN VIN C1 1µF SW OVP UTC L5101 SHDN GND PWM FB R3 5.1K C2 1µF R1 1K R2 51K C3 0.1µF RFB 4.7Ω Fig. 5 Dimming Control Using a Filter PWM Signal UNISONIC TECHNOLOGIES CO., LTD www.unisonic.com.tw 7 of 10 QW-R103-026.B L5101 LINEAR INTEGRATED CIRCUIT TYPICAL APPLICATION CIRCUIT Fig. 6 Six White LEDs Application in Li-Ion Battery UNISONIC TECHNOLOGIES CO., LTD www.unisonic.com.tw 8 of 10 QW-R103-026.B L5101 TYPICAL CHARACTERISTICS Switching Frequency (MHz) Feedback Voltage (mV) LINEAR INTEGRATED CIRCUIT Supply Current vs. Supply Voltage Supply Current vs. Supply Voltage 1.95 1.35 Supply Current (mA) 1.34 1.90 1.33 1.32 FB=VIN Non-Switching 1.31 1.85 FB=GND Switching 1.30 1.80 1.29 2.5 3.0 3.5 4.0 4.5 5.0 2.5 5.5 6.0 3.5 4.0 4.5 5.0 5.5 6.0 Supply Voltage (V) Supply Voltage (V) 3LEDs Efficiency vs. LED Current RDS(ON) vs. Supply Voltage 1.4 3.0 90 VIN=3.6V 85 VIN=3.0V 80 Efficiency (%) RDS(ON) (Ω) 1.3 1.2 1.1 75 3LEDs, L1=10μH 70 65 VIN=4.2V 60 55 1.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 Supply Voltage (V) UNISONIC TECHNOLOGIES CO., LTD www.unisonic.com.tw 0 5 10 15 20 LED Current (mA) 9 of 10 QW-R103-026.B L5101 TYPICAL CHARACTERISTICS 4LEDs Efficiency vs. LED Current 90 VIN=3.6V 85 VIN=3.0V 80 Efficiency (%) LINEAR INTEGRATED CIRCUIT 4LEDs, L1=10μH 75 70 65 VIN=4.2V 60 0 5 10 15 20 LED Current (mA) UTC assumes no responsibility for equipment failures that result from using products at values that exceed, even momentarily, rated values (such as maximum ratings, operating condition ranges, or other parameters) listed in products specifications of any and all UTC products described or contained herein. UTC products are not designed for use in life support appliances, devices or systems where malfunction of these products can be reasonably expected to result in personal injury. Reproduction in whole or in part is prohibited without the prior written consent of the copyright owner. The information presented in this document does not form part of any quotation or contract, is believed to be accurate and reliable and may be changed without notice. UNISONIC TECHNOLOGIES CO., LTD www.unisonic.com.tw 10 of 10 QW-R103-026.B