Pb AP5724 WHITE LED STEP-UP CONVERTER Description Pin Assignments The AP5724 is a step-up DC/DC converter specifically designed to (Top View) drive white LEDs with a constant current. The device can drive 2 ~ 6 LEDs in series from a Li-Ion cell. Series connection of the LEDs 1 VIN SW 6 provides identical LED currents resulting in uniform brightness and eliminates the need for ballast resistors. For driving higher number of GND 2 5 OVP LEDs, AP5724 also supports a single feedback of parallel connected multiple strings of equal number of LEDs. 74 FB 3 EN The AP5724 switches at 1.2MHz that allows the use of tiny external components. A low 0.1V feedback voltage minimizes power loss in SOT26 / TSOT23-6 the current setting resistor for better efficiency (Top View) Features SW 1 6 GND High Efficiency: 84% Typical Fast 1.2MHz Switching Frequency 2 5 V FB IN Current Limit and UVLO Protections Internal Thermal Shutdown 3 4 OVP EN Internal Over Voltage Protection Integrated Soft-Start Function U-DFN2020-6 SOT26, TSOT26 and U-DFN2020-6: Available in Green Molding Compound (No Br, Sb) Applications Lead-Free Finish RoHS Compliant (Notes 1 & 2) Cellular Phones PDAs, Hand held Computers Digital Cameras MP3 Players GPS Receivers Notes: 1. EU Directive 2002/95/EC (RoHS) & 2011/65/EU (RoHS 2) compliant. All applicable RoHS exemptions applied. 2. See - + AP5724 Pin Descriptions Pin Name Functions SW Switch Pin. Connect inductor/diode here. Minimize trace area at this pin to reduce EMI. GND GND pin. Feedback Pin. Reference voltage is 0.1V. Connect cathode of lowest LED and a sense resister here. Calculate resistor value FB according to the formula: R = 0.1V / ILED SET Converter On/Off Control Input. A high input at EN turns the converter On, and a low input turns it off. If On/Off control is not EN needed, connect EN to the input source for automatic startup. The EN pin cannot be left floating. OVP Output Voltage detect pin for over voltage protection. V Input Supply Pin. Must be locally bypassed with 1 F or 2.2 F to reduce input noise. IN Functional Block Diagram OVP 5 1 SW Comparator Driver A2 Q1 CONTROL LOGIC Rc OTP A1 - + Cc FB 3 V REF V 6 IN 0.1V RAMP Generator 2 GND EN 4 Enable 1.2MHz Oscillator Absolute Maximum Ratings ( T = +25C, unless otherwise specified.) A Symbol Parameter Rating Unit V VIN Pin Voltage -0.3 to +7 V IN VSW SW Voltage -0.3 to +34 V V OVP Pin Voltage -0.3 to +35 V OVP V Feedback Pin Voltage -0.3 to +7 V FB EN EN -0.3 to +7 V T Maximum Junction Temperature 150 C J(MAX) T Lead Temperature 300 C LEAD Storage Temperature Range -65 to +150 C T ST Caution: Operation above the absolute maximum ratings can cause device failure. These values, therefore, must not be exceeded under any condition. Operation at the absolute maximum rating for extended periods, may reduce device reliability. 2 of 15 December 2013 AP5724 Diodes Incorporated www.diodes.com Document number: DS31843 Rev. 4 - 2 - +