UNISONIC TECHNOLOGIES CO., LTD L5101 LINEAR INTEGRATED CIRCUIT 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. 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 www.unisonic.com.tw Copyright © 2005 Unisonic Technologies Co., Ltd Package Packing SOT-26 Tape Reel 1 of 9 QW-R103-026,A L5101 LINEAR INTEGRATED CIRCUIT PIN CONFIGURATION OVP VIN SW 6 5 4 1 2 3 SHDN GND FB PIN DESCRIPTIONS 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. Overvoltage protection OVP The internal MOSFET will turn off when VOUT >27V. UNISONIC TECHNOLOGIES CO., LTD www.unisonic.com.tw 2 of 9 QW-R103-026,A L5101 LINEAR INTEGRATED CIRCUIT BLOCK DIAGRAM Over Voltage Comparator - OVP SHDN PWM/PFM Control + 27V SW VIN 95mV VREF Control Logic + M1 Driver - + Error AMP M FB PWM Comparator RC 1.2MHz Oscillator Slope Compensation CC Internal Soft Start + Current AMP. UNISONIC TECHNOLOGIES CO., LTD www.unisonic.com.tw - RS GND 3 of 9 QW-R103-026,A L5101 LINEAR INTEGRATED CIRCUIT ABSOLUTE MAXIMUM RATINGS 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 VFB IFB TEST CONDITIONS Switching Non switching VSHDN=0V fSW DC ON OFF RIN(OVP) VTHR(OVP) 1V Hysteresis typical MAX 5.5 5 100 1.0 UNIT V mA µA 85 95 1 105 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 RON(SW) ILEAK (SW)) VSW =33V VIH(SHDN) VIL(SHDN) TYP 1 70 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 9 QW-R103-026,A L5101 LINEAR INTEGRATED CIRCUIT TEST CIRCUIT L1 10μH VIN C1 1μF D1 C2 0.22μF RB521S-30 VIN SW SHDN OVP GND ILED FB L5101 RFB 4.7Ω UNISONIC TECHNOLOGIES CO., LTD www.unisonic.com.tw 5 of 9 QW-R103-026,A 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 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 L 10μH VIN C1 1μF D1 C2 1μF RB521S-30 VIN SW SHDN OVP GND FB 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 VIN C1 1μF D1 RB521S-30 VIN SW SHDN OVP GND FB L5101 PWM R2 51KΩ R1 1KΩ 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 LINEAR INTEGRATED CIRCUIT APPLICATION INFORMATION(Cont.) 2. Using a DC Voltage L 10μH VIN C1 1μF VIN D1 SW SHDN C2 1μF RB521S-30 OVP GND FB VDC 0~5V L5101 R2 51KΩ R1 1KΩ RFB 4.7Ω Fig.3 Dimming Control Using a DC Voltage 3. Using a Filtered PWM Signal L 10μH VIN C1 1μF D1 C2 1μF RB521S-30 VIN SW SHDN OVP GND FB R1 1KΩ L5101 PWM R3 5.1KΩ R2 51KΩ RFB 4.7Ω C3 0.1μF 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 LINEAR INTEGRATED CIRCUIT TYPICAL CHARACTERISTICS Supply Current vs. Supply Voltage (V) Supply Current vs. Supply Voltage (V) 1.6 70 FB=GND 60 Supply Current (mA) Supply Current (μA) 1.4 FB=VIN 50 40 Non-Switching 30 2 4 3 5 1.2 1.0 0.8 Switching 0.6 2 6 3 Supply Voltage (V) 6 5 4 Supply Voltage (V) RDS-ON vs. Supply Voltage (V) 3 LEDs Efficiency vs. LED Current 1.4 90 1.3 85 1.2 80 Effciency (%) RDSON (O ) VIN = 4.2V 1.1 1.0 0.9 75 70 3 LEDs, 6.8μH L1: 976AS-6R8M, TOKO D1: RB521S-30, ROHM 65 0.8 2.5 3.0 3.5 4.5 4.0 5.0 5.5 60 6.0 VIN = 3.6V VIN = 3.0V 0 5 Supply Voltage (V) 15 10 20 LED Current (mA) 3 LEDs Efficiency vs. LED Current 4 LEDs Efficiency vs. LED Current 90 90 V IN = 4.2V 85 VIN = 4.2V 85 80 Effciency (%) Effciency (%) VIN = 3.0V VIN = 3.6V 75 70 3 LEDs, 10μH L1: 976AS-100M, TOKO D1: RB521S-30, ROHM 65 60 0 5 10 15 VIN = 3.6V 75 VIN = 3.0V 70 4 LEDs, 10μH L1: 976AS-100M, TOKO D1: RB521S-30, ROHM 65 20 LED Current (mA) UNISONIC TECHNOLOGIES CO., LTD www.unisonic.com.tw 80 60 0 5 10 20 15 LED Current (mA) 8 of 9 QW-R103-026,A L5101 LINEAR INTEGRATED CIRCUIT TYPICAL CHARACTERISTICS(cont.) 5 LEDs Efficiency vs. LED Current 90 VIN = 4.2V Effciency (%) 85 80 VIN = 3.6V 75 VIN = 3.0V 70 5 LEDs, 10μH L1: 976AS-100M, TOKO D1: RB521S-30, ROHM 65 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 9 of 9 QW-R103-026,A