L5101

UNISONIC TECHNOLOGIES CO., LTD L5101 WHITE LED STEP-UP CONVERTER DESCRIPTION The UTC L5101 is a fixed frequency step-up PWM DC/DC converter and designed for white LEDS driving with a constant current to provide backlight in handheld devices. The device switches at a high frequency 1.2MHz by an internal N-channel MOSFET switch to be capable of minimum external components using. The UTC L5101 can drive up to 5 LEDs in series by a Li-Ion cell. Series connection of LEDS provides identical LED currents resulting in uniform brightness without ballast resistors. The low 95mV feedback voltage minimizes power loss in the current setting resistor can have better efficiency. LINEAR INTEGRATED CIRCUIT 6 5 4 1 2 3 SOT-26 *Pb-free plating product number: L5101L FEATURES * Built-In Open Circuit Protection * Built-In Over Voltage Protection * High Efficiency(Up to 84% at VIN=4.2V, 3 LEDs, ILED=20mA) * 1.2MHz fixed switching frequency * Low supply current: 70µA * Matches LED current * Requires tiny inductor and capacitors ORDERING INFORMATION Order Number Normal Lead Free Plating L5101-AG6-R L5101L-AG6-R Package SOT-26 Packing Tape Reel www.unisonic.com.tw Copyright © 2005 Unisonic Technologies Co., Ltd 1 of 9 QW-R103-026,A L5101 PIN CONFIGURATION LINEAR INTEGRATED CIRCUIT OVP 6 VIN 5 SW 4 1 SHDN PIN DESCRIPTIONS PIN NO. 1 2 3 4 5 6 2 GND 3 FB 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. Overvoltage protection OVP The internal MOSFET will turn off when VOUT >27V. PIN NAME Shutdown Ground UNISONIC TECHNOLOGIES CO., LTD www.unisonic.com.tw 2 of 9 QW-R103-026,A L5101 BLOCK DIAGRAM Over Voltage Comparator 27V OVP + - LINEAR INTEGRATED CIRCUIT PWM/PFM Control SHDN SW VIN 95mV VREF + Error AMP M PWM Comparator Control Logic Driver M1 + FB - 1.2MHz Oscillator Slope Compensation + Current AMP. RS GND RC CC Internal Soft Start UNISONIC TECHNOLOGIES CO., LTD www.unisonic.com.tw 3 of 9 QW-R103-026,A L5101 ABSOLUTE MAXIMUM RATINGS LINEAR INTEGRATED CIRCUIT 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 0 ~ +70 ℃ Storage Temperature Range TSTG -40 ~ +150 ℃ Note 1. 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. 2. The device is guaranteed to meet performance specification within 0℃ ~ +70℃ operating temperature range and assured by design from –20℃ ~ +85℃. 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 TEST CONDITIONS Switching Non switching VSHDN=0V 85 VFB=95mV 0.8 85 MIN 2.5 TYP 1 70 0.1 95 1 1.2 90 1.4 0.1 1.5 0.3 0.6 22 1.2 27 1.8 32 MAX 5.5 5 100 1.0 105 UNIT V mA µA mV nA MHz % Ω µA V V MΩ V VFB IFB fSW DC 1.6 RON(SW) ILEAK (SW)) VSW =33V VIH(SHDN) VIL(SHDN) ON OFF 5 1 RIN(OVP) VTHR(OVP) 1V Hysteresis typical UNISONIC TECHNOLOGIES CO., LTD www.unisonic.com.tw 4 of 9 QW-R103-026,A L5101 TEST CIRCUIT LINEAR INTEGRATED CIRCUIT VIN C1 1μF L1 10μH D1 RB521S-30 C2 0.22μF VIN SHDN GND SW OVP FB ILED L5101 RFB 4.7Ω UNISONIC TECHNOLOGIES CO., LTD www.unisonic.com.tw 5 of 9 QW-R103-026,A L5101 APPLICATION INFORMATION Recommended Component Selection LINEAR INTEGRATED CIRCUIT Inductor Selection: A 10µH inductor is recommended for most applications. Capacitor Selection: The small size of ceramic capacitors (1µF input with 1µF output ) are sufficient, X5R and X7R types are recommended Diode Selection: An Schottky diode rated at 100mA ~ 200mA is sufficient for most applications. 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 VIN C1 1μF L 10μH D1 RB521S-30 VIN SHDN GND SW OVP FB C2 1 μF L5101 RFB 4.7Ω Fig.1 Dimming Control with a PWM Signal Open-Circuit Protection When a high output voltage exceeds maximum 33V, the built-in OVP (Over Voltage Protection) will be triggered to prevent the damage resulting from an open circuit condition. Dimming Control There are three different ways of dimming control circuits as follows: 1. Using a PWM signal L 10μH C1 1μF D1 VIN RB521S-30 VIN SHDN GND SW OVP FB PWM R2 51KΩ R1 1KΩ L5101 RFB 4.7Ω Fig.2 Dimming Control Using a PWM Signal UNISONIC TECHNOLOGIES CO., LTD www.unisonic.com.tw 6 of 9 QW-R103-026,A L5101 APPLICATION INFORMATION(Cont.) 2. Using a DC Voltage L 10μH C1 1 μF D1 LINEAR INTEGRATED CIRCUIT VIN VIN SHDN GND SW OVP FB RB521S-30 C2 1 μF L5101 VDC 0~5V R2 51KΩ R1 1KΩ RFB 4.7Ω Fig.3 Dimming Control Using a DC Voltage 3. Using a Filtered PWM Signal L 10μH C1 1 μF D1 C2 1 μF VIN RB521S-30 VIN SHDN GND SW OVP FB R3 5.1KΩ C3 0.1μF R1 1KΩ R2 51KΩ RFB 4.7Ω L5101 PWM Fig.4 Dimming Control Using a Filter PWM Signal UNISONIC TECHNOLOGIES CO., LTD www.unisonic.com.tw 7 of 9 QW-R103-026,A L5101 TYPICAL CHARACTERISTICS Supply Current vs. Supply Voltage (V) 70 LINEAR INTEGRATED CIRCUIT Supply Current vs. Supply Voltage (V) 1.6 1.4 FB=GND Supply Current (μA) Supply Current (mA) 60 FB=VIN 50 1.2 1.0 0.8 0.6 Switching 2 3 4 5 6 40 Non-Switching 30 2 3 4 5 6 Supply Voltage (V) Supply Voltage (V) RDS-ON vs. Supply Voltage (V) 1.4 1.3 Effciency (%) 1.2 RDSON (O ) 1.1 1.0 0.9 0.8 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 90 3 LEDs Efficiency vs. LED Current VIN = 4.2V 85 80 75 70 65 60 0 5 3 LEDs, 6.8μH L1: 976AS-6R8M, TOKO D1: RB521S-30, ROHM 10 15 20 VIN = 3.0V VIN = 3.6V Supply Voltage (V) LED Current (mA) 3 LEDs Efficiency vs. LED Current 90 85 VIN = 3.0V Effciency (%) 4 LEDs Efficiency vs. LED Current 90 VIN = 4.2V V IN = 4.2V 85 Effciency (%) 80 VIN = 3.6V 75 70 65 60 0 5 3 LEDs, 10μH L1: 976AS-100M, TOKO D1: RB521S-30, ROHM 10 15 20 80 75 VIN = 3.0V 70 65 60 0 5 4 LEDs, 10μH L1: 976AS-100M, TOKO D1: RB521S-30, ROHM 10 15 20 VIN = 3.6V LED Current (mA) LED Current (mA) UNISONIC TECHNOLOGIES CO., LTD www.unisonic.com.tw 8 of 9 QW-R103-026,A L5101 TYPICAL CHARACTERISTICS(cont.) 5 LEDs Efficiency vs. LED Current 90 85 Effciency (%) 80 VIN = 3.6V 75 70 65 60 0 5 5 LEDs, 10μH L1: 976AS-100M, TOKO D1: RB521S-30, ROHM 10 15 20 VIN = 3.0V VIN = 4.2V LINEAR INTEGRATED CIRCUIT LED Current (mA) U TC 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 9 of 9 QW-R103-026,A