AP5724 WHITE LED STEP-UP CONVERTER General Description Features • • • • • • • • • The AP5724 is a step-up DC/DC converter specifically designed to 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 provides identical LED currents resulting in uniform brightness and eliminates the need for ballast resistors. The AP5724 switches at 1.2MHz that allows the use of tiny external components. A low 0.1V feedback voltage minimizes power loss in the current setting resistor for better efficiency. Inherently Matched LED Current High Efficiency: 84% Typical Fast 1.2MHz Switching Frequency Current limit and UVLO Protections Internal Thermal Shutdown Internal Over Voltage Protection Integrated Soft-start Function SOT26 and DFN2020C-6: Available in “Green” Molding Compound (No Br, Sb) Lead Free Finish/RoHS Compliant (Note 1) Applications • • • • • Cellular Phones PDAs, Hand held Computers Digital Cameras MP3 Players GPS Receivers Typical Application Circuit L1 22uH VIN D1 COUT 1uF C IN 1uF V IN ON OFF PWM Dimming SW AP5724 OVP EN FB GND 2~6 LEDs RSET 5 Figure 1. Typical Application Circuit AP5724 Rev. 1 1 of 16 www.diodes.com JUNE 2009 © Diodes Incorporated AP5724 WHITE LED STEP-UP CONVERTER Ordering Information AP 5724 XXX G - 7 Package Green W : SOT26 FDC : DFN2020C-6 G : Green Device Package Code Packaging (Note 2) W FDC SOT26 DFN2020C-6 AP5724WG-7 AP5724FDCG-7 Notes: Packing 7 : Tape & Reel 13” Tape and Reel Quantity Part Number Suffix 3000/Tape & Reel 3000/Tape & Reel -7 -7 1. EU Directive 2002/95/EC (RoHS). All applicable RoHS exemptions applied. Please visit our website at http://www.diodes.com/products/lead_free.html 2. Pad layout as shown on Diodes Inc. suggested pad layout document AP02001, which can be found on our website at http://www.diodes.com/datasheets/ap02001.pdf. Pin Assignments (1) SOT26 (2) DFN2020C-6 ( Top View ) SW 1 ( Top View ) 6 VIN GND 2 5 OVP FB 3 74 EN SW 1 6 GND VIN 2 5 FB OVP 3 4 EN Pin Descriptions Pin Name SW GND FB EN OVP VIN AP5724 Rev. 1 Description Switch Pin. Connect inductor/diode here. Minimize trace area at this pin to reduce EMI. GND pin. Feedback Pin. Reference voltage is 0.1V. Connect cathode of lowest LED and resister here. Calculate resistor value according to the formula: RSET = 0.1V / ILED Converter On/Off Control Input. A high input at EN turn on the converter, and a low input turns it off. When not used, connect EN to the input source for automatic startup. The EN pin cannot be left floating. Output Voltage detect pin for over voltage protection. Input Supply Pin. Must be locally bypassed with 1μF or 2.2μF to reduce input noise. 2 of 16 www.diodes.com JUNE 2009 © Diodes Incorporated AP5724 WHITE LED STEP-UP CONVERTER Block Diagram OVP 5 1 SW Comparator - Driver Q1 A2 + Rc - CONTROL LOGIC OTP A1 + Cc VREF 0.1V Σ - VIN 6 + FB 3 RAMP Generator EN 4 2 GND Enable 1.2MHz Oscillator Absolute Maximum Ratings Symbol Parameter Rating Unit VIN VIN Pin Voltage -0.3~7 V VSW SW Voltage -0.3~34 V VOVP OVP Pin Voltage -0.3~35 V VFB Feedback Pin Voltage -0.3~7 V EN EN -0.3~7 TJ(MAX) TLEAD TST Maximum Junction Temperature Lead Temperature Storage Temperature Range V 150 o C 300 o C -65 to +150 o C Caution: The absolute maximum ratings are rated values exceeding which the product could suffer physical damage. These values must therefore not be exceeded under any condition. AP5724 Rev. 1 3 of 16 www.diodes.com JUNE 2009 © Diodes Incorporated AP5724 WHITE LED STEP-UP CONVERTER Recommended Operating Conditions Symbol VIN TJ TA Parameter Input Voltage Operating Junction Temperature Operating Ambient Temperature Electrical Characteristics Symbol Parameter System Supply Input VIN Operating Input Voltage UVLO Under Voltage Lockout Under Voltage Lockout Hysteretic IQ Quiescent Current ISD Shutdown Current Oscillator FOSC Operation Frequency Dmax Maximum Duty Cycle Reference Voltage VFB Feedback Voltage IFB FB Pin Bias Current MOSFET Rds(on) On Resistance of MOSFET IOCP Switching Current Limit Control and Protection EN Voltage High EN Voltage Low IEN EN Pin Pull Low Current OVP OVP Threshold Thermal Resistance θJA Junction-to-Ambient Thermal Resistance θJC Junction-to-Case Notes: Min 2.7 -40 -40 Max 5.5 125 85 Unit V o C o C (VIN=3.6V, TA=25oC, unless otherwise specified.) Conditions FB=0.2V, No Switching VEN < 0.4V Normal Operation ON OFF SOT26 (Note 3) DFN2020C-6 (Note 3) SOT26 (Note 3) DFN2020C-6 (Note 3) Min Typ. Max Unit 2.7 - 2.2 5.5 2.4 V V - 85 - mV - 500 0.1 1 μA μA 1 86 1.2 90 1.4 - MHz % 0.09 10 0.1 45 0.11 100 V nA 0.5 - 0.75 750 1.0 - Ω mA 1.5 26 4 30 162 200 36 30 0.4 6 34 V V μA V o C/W o C/W o C/W o C/W 3. Test condition for SOT26 and DFN2020C-6: Device mounted on FR-4 substrate, single-layer PC board, 2oz copper, with minimum recommended pad layout AP5724 Rev. 1 4 of 16 www.diodes.com JUNE 2009 © Diodes Incorporated AP5724 WHITE LED STEP-UP CONVERTER Typical Performance Characteristics (6 LEDs ; VIN = 3.6V ; IOUT = 25mA) VIN vs. Shutdown Current VIN vs. Quiescent Current 700 Quiescent Current(uA) Shutdown Current(uA) 1 0.8 0.6 0.4 0.2 600 500 400 300 200 100 0 2.5 3 3.5 4 4.5 5 0 5.5 2.5 VIN (V) 3 4.5 5 5.5 100 1.2 95 Max Duty(%) Frequency(MHz) 4 VIN (V) VIN vs. Max Duty VIN vs. Frequency 1.25 1.15 1.1 90 85 1.05 1 80 2.5 3 3.5 4 VIN (V) 4.5 5 5.5 2.5 3 VIN vs. Feedback Voltage 3.5 4 VIN(V) 4.5 5 5.5 IOUT vs. Feedback Voltage 0.12 0.12 0.11 0.11 Feedback Voltage(V) Feedback Voltage(V) 3.5 0.1 0.09 0.08 0.07 0.1 0.09 0.08 0.07 0.06 0.06 2.5 AP5724 Rev. 1 3 3.5 4 VIN (V) 4.5 5 5.5 5 of 16 www.diodes.com 0 10 20 30 IOUT (mA) 40 50 JUNE 2009 © Diodes Incorporated AP5724 WHITE LED STEP-UP CONVERTER Typical Performance Characteristics (Continued) Temperature vs. Shutdown Current VIN vs. OVP Threshold 1 Shutdown Current(uA) OVP Threshold(V) 35 33 31 29 27 0.8 0.6 0.4 0.2 25 0 2.5 3 3.5 4 VIN (V) 4.5 5 5.5 -50 -25 0 25 50 75 Temperature (℃) 100 125 Tem perature vs. Frequency Temperature vs. OVP Threshold 35 1.7 30 1.4 Frequency (MHZ) OVP Threshold(V) V IN = 4.2V 25 20 15 10 1.1 V IN = 3.6V 0.8 0.5 0.2 -50 -25 0 25 50 75 Temperature (℃) 100 125 -50 -25 0 25 50 75 Tem perature (℃) 100 125 Temperature vs. Feedback Voltage Feedback Voltage(mV) 120 VIN = 4.2V 110 100 VIN = 3.6V 90 80 70 60 -50 -25 AP5724 Rev. 1 0 25 50 75 Temperature (℃) 100 125 6 of 16 www.diodes.com JUNE 2009 © Diodes Incorporated AP5724 WHITE LED STEP-UP CONVERTER Typical Performance Characteristics (Continued) IOUT vs. Efficiency IOUT vs. Efficiency 90 90 VIN = 4.2V 85 80 75 Efficiency(%) Efficiency(%) 85 VIN = 3.6V 70 65 VIN = 4.2V 80 75 VIN = 3.6V 70 65 4 LEDs ; L = 22uH 6 LEDs ; L = 22uH 60 60 0 5 10 15 IOUT (mA) 20 25 30 0 5 10 15 IOUT (mA) 20 25 30 VIN vs. Efficiency 100 3 LEDs Efficiency(%) 90 4 LEDs 80 6 LEDs 70 60 50 40 2.5 3 3.5 4 4.5 5 VIN (V) AP5724 Rev. 1 7 of 16 www.diodes.com JUNE 2009 © Diodes Incorporated AP5724 WHITE LED STEP-UP CONVERTER Typical Performance Characteristics (Continued) VOUT Ripple VIN = 3.6V; 4 LEDs ; IOUT = 30mA VOUT Ripple VIN = 3.6V; 6 LEDs ; IOUT = 30mA SW SW VOUT VOUT POWER ON VIN = 3.6V; 6 LEDs ; IOUT = 30mA AP5724 Rev. 1 POWER OFF VIN = 3.6V; 6 LEDs ; IOUT = 30mA VEN VEN VOUT VOUT Irushing Irushing 8 of 16 www.diodes.com JUNE 2009 © Diodes Incorporated AP5724 WHITE LED STEP-UP CONVERTER Application Information Inductor Selection A 10μH~22μH inductor is recommended for most AP5724 applications. Although small size and high efficiency are major concerns, the inductor should have low core losses at 1.2MHz and low DCR (copper wire resistance). Capacitor Selection The small size of ceramic capacitors are ideal for AP5724 applications. X5R and X7R types are recommended because they retain their capacitance over wider voltage and temperature ranges than other types such as Y5V or Z5U. A 1μF input capacitor and a 1μF output capacitor are sufficient for most AP5724 applications. Diode Selection Schottky diodes, with their low forward voltage drop and fast reverse recovery, are the ideal choices for AP5724 applications. The forward voltage drop of a Schottky diode represents the conduction losses in the diode, while the diode capacitance (CT or CD) represents the switching losses. For diode selection, both forward voltage drop and diode capacitance need to be considered. Schottky diodes with higher current ratings usually have lower forward voltage drop and larger diode capacitance, which can cause significant switching losses at the 1.2MHz switching frequency of the AP5724. A Schottky diode rated at 100mA to 200mA is sufficient for most AP5724 applications. LED Current Control The LED current is controlled by the feedback resistor (RSET in Figure 1). The feedback reference is 0.1V. The LED current is 0.1V/ RSET. In order to have accurate LED current, precision resistors are preferred (1% is recommended). The formula and table for RSET selection are shown below. RSET = 0.1V/ILED (See Table 1) Table 1. RSET Resistor Value Selection ILED (mA) 5 10 15 20 30 AP5724 Rev. 1 RSET (Ω) 20 10 6.6 5 3.3 9 of 16 www.diodes.com JUNE 2009 © Diodes Incorporated AP5724 WHITE LED STEP-UP CONVERTER Application Information (Continued) Open-Circuit Protection In the cases of output open circuit, when the LEDs are disconnected from the circuit or the LEDs fail, the feedback voltage will be zero. The AP5724 will then switch at a high duty cycle resulting in a high output voltage, which may cause the SW pin voltage to exceed the level of the over voltage protect function. The OVP pin can detect the output voltage and monitor if the output voltage reach to the protect voltage level (Figure 2). Once OVP is activated, SW pin stops switching. L1 22uH VIN D1 COUT 1uF C IN 1uF V IN SW x AP5724 OVP EN x FB GND RSET 5 Figure 2. LED Driver with Open-Circuit Protection Dimming Control There are four different types of dimming control circuits: 1. Using a PWM Signal to EN Pin With the PWM signal applied to the EN pin, the AP5724 is turned on or off by the PWM signal. The LEDs operate at either zero or full current. The average LED current increases proportionally with the duty cycle of the PWM signal. A 0% duty cycle will turn off the AP5724 and corresponds to zero LED current. A 100% duty cycle corresponds to full current. The typical frequency range of the PWM signal is below 2 kHz. AP5724 Rev. 1 10 of 16 www.diodes.com JUNE 2009 © Diodes Incorporated AP5724 WHITE LED STEP-UP CONVERTER Application Information (Continued) 2. Using a DC Voltage For some applications, the preferred method of brightness control is a variable DC voltage to adjust the LED current. The dimming control using a DC voltage is shown in Figure 3. As the DC voltage increases, the voltage drop on R2 increases and the voltage drop on RSET decreases. Thus, the LED current decreases. The selection of R2 and R3 will make the current from the variable DC source much smaller than the LED current and much larger than the FB pin bias current. For VDC range from 0V to 2V, the selection of resistors in Figure 3 gives dimming control of LED current from 0mA to 20mA. 3. Using a Filtered PWM Signal The filtered PWM signal can be considered as an adjustable DC voltage. It can be used to replace the variable DC voltage source in dimming control. AP5724 FB VDC R3 100k R2 5k RSET 5 Figure 3. Dimming Control Using a DC Voltage 4. Using a Logic Signal For applications that need to adjust the LED current in discrete steps, a logic signal can be used as shown in Figure 4. RSET sets the minimum LED current (when the NMOS is off). RSET sets how much the LED current increases when the NMOS is turned on. AP5724 FB RINC Logic Signal RSET Figure 4. Dimming Control Using a Logic Signal AP5724 Rev. 1 11 of 16 www.diodes.com JUNE 2009 © Diodes Incorporated AP5724 WHITE LED STEP-UP CONVERTER Application Circuit VOUT VIN L1 C1 1uF D2 D1 B0540WS C2 1uF U1 LED 1 SW 2 GND D3 LED 22uH R1 5ohm 3 Vin OVP FB EN 6 5 4 ON OFF AP5724 D4 LED D5 LED D6 LED D7 LED Table 2. Suggested Inductors Inductors Vendor (uH) Current Rating (A) Type Dimensions (mm) Series Wurth Electronics 22 0.51A SMD 3.8X 3.8 X 1.6 744031220 GOTREND 22 0.56A SMD 3.8 X 3.8 X 1.05 GLP3810PH220N TAIYO YUDRN 22 0.51A SMD 4.0 X 4.0 X 1.25 NR4012 Table 3. Suggested Capacitors for CIN and COUT Vendor Capacitance Type Series TAIYO YUDEN 1uF SMD TMK212 B7105MG-T Type Series Table 4. Suggested Diodes Vendor Rating ZETEX 40V/0.5A SOD323 ZLLS400 DIODES 40V/0.5A SOD323 B0540WS DIODES 40V/0.25A SOD523 SDM20U40 Table 5. Suggested Resistor Vendor Type YAGEO SMD Series FR-SK Table 6. Suggested W-LED Vendor Type LITEON SMD Series LTW-C1911UC5 AP5724 Rev. 1 12 of 16 www.diodes.com JUNE 2009 © Diodes Incorporated AP5724 WHITE LED STEP-UP CONVERTER Marking Information (1) SOT26 ( Top View ) 5 4 7 6 XX : Identification Code Y : Year 0~9 W : Week : A~Z : 1~26 week; a~z : 27~52 week; z represents 52 and 53 week X : A~Z : Green XX Y W X 1 2 Part Number AP5724 3 Package SOT26 Identification Code FB (2) DFN2020C-6 ( Top View ) XX YWX Part Number AP5724 AP5724 Rev. 1 XX : Identification Code Y : Year : 0~9 W : Week : A~Z : 1~26 week; a~z : 27~52 week; z represents 52 and 53 week X : A~Z : Green Package DFN2020C-6 13 of 16 www.diodes.com Identification Code GB JUNE 2009 © Diodes Incorporated AP5724 WHITE LED STEP-UP CONVERTER Package Information (All Dimensions in mm) (1) Package Type: SOT26 0.43mon. 0.57/0.63 (2) Package Type: DFN2020C-6 Marking 0.15max. 0.10 C 0.25 A Pin#1 ID 2x 0/0.05 0.08 C B 1.95/2.075 1.55/1.75 (Active area depth) Seating plane C A 2x- 0.25/0.35 0.86/1.06 1.95/2.075 R0. 15 1 R0. 0.25 B 0.65nom. 0.25/0.35 0.10 M C A B Bottom View AP5724 Rev. 1 14 of 16 www.diodes.com JUNE 2009 © Diodes Incorporated AP5724 WHITE LED STEP-UP CONVERTER Taping Orientation (1) DFN2020C-6 Notes: 4. The taping orientation of the other package type can be found on our website at http://www.diodes.com/datasheets/ap02007.pdf. AP5724 Rev. 1 15 of 16 www.diodes.com JUNE 2009 © Diodes Incorporated AP5724 WHITE LED STEP-UP CONVERTER IMPORTANT NOTICE DIODES INCORPORATED MAKES NO WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, WITH REGARDS TO THIS DOCUMENT, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE (AND THEIR EQUIVALENTS UNDER THE LAWS OF ANY JURISDICTION). Diodes Incorporated and its subsidiaries reserve the right to make modifications, enhancements, improvements, corrections or other changes without further notice to this document and any product described herein. Diodes Incorporated does not assume any liability arising out of the application or use of this document or any product described herein; neither does Diodes Incorporated convey any license under its patent or trademark rights, nor the rights of others. Any Customer or user of this document or products described herein in such applications shall assume all risks of such use and will agree to hold Diodes Incorporated and all the companies whose products are represented on Diodes Incorporated website, harmless against all damages. Diodes Incorporated does not warrant or accept any liability whatsoever in respect of any products purchased through unauthorized sales channel. Should Customers purchase or use Diodes Incorporated products for any unintended or unauthorized application, Customers shall indemnify and hold Diodes Incorporated and its representatives harmless against all claims, damages, expenses, and attorney fees arising out of, directly or indirectly, any claim of personal injury or death associated with such unintended or unauthorized application. Products described herein may be covered by one or more United States, international or foreign patents pending. Product names and markings noted herein may also be covered by one or more United States, international or foreign trademarks. LIFE SUPPORT Diodes Incorporated products are specifically not authorized for use as critical components in life support devices or systems without the express written approval of the Chief Executive Officer of Diodes Incorporated. As used herein: A. Life support devices or systems are devices or systems which: 1. are intended to implant into the body, or 2. support or sustain life and whose failure to perform when properly used in accordance with instructions for use provided in the labeling can be reasonably expected to result in significant injury to the user. B. A critical component is any component in a life support device or system whose failure to perform can be reasonably expected to cause the failure of the life support device or to affect its safety or effectiveness. Customers represent that they have all necessary expertise in the safety and regulatory ramifications of their life support devices or systems, and acknowledge and agree that they are solely responsible for all legal, regulatory and safety-related requirements concerning their products and any use of Diodes Incorporated products in such safety-critical, life support devices or systems, notwithstanding any devices- or systems-related information or support that may be provided by Diodes Incorporated. Further, Customers must fully indemnify Diodes Incorporated and its representatives against any damages arising out of the use of Diodes Incorporated products in such safety-critical, life support devices or systems. Copyright © 2009, Diodes Incorporated www.diodes.com AP5724 Rev. 1 16 of 16 www.diodes.com JUNE 2009 © Diodes Incorporated