AP5726 WHITE LED STEP-UP CONVERTER Description Pin Assignments (Top View) The AP5726 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. For driving higher number of LEDs, AP5726 also supports a single feedback of parallel connected multiple strings of equal number of LEDs. SW 1 6 VIN GND 2 5 OVP 3 74 FB EN (Top View) SW 1 6 GND VIN 2 5 FB OVP 3 4 EN SOT26 / TSOT23-6 The AP5726 switches at 1.2MHz that allows the use of tiny external components. A low 0.31V feedback voltage minimizes power loss in the current setting resistor for better efficiency. Features Applications • • • • • • • • • • • • • 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, TSOT23-6 and DFN2020C-6: Available in “Green” Molding Compound (No Br, Sb) Lead Free Finish/ RoHS Compliant (Note 1) Notes: DFN2020C-6 Cellular Phones PDAs, Hand help Computers Digital Cameras MP3 Players GPS Receivers 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. Typical Application Circuit L1 22uH VIN D1 COUT 1uF C IN 1uF V IN ON OFF PWM Dimming SW 2~6 LEDs AP5726 OVP EN FB GND RSET 15 Figure 1. Typical Application Circuit AP5726 Document number: DS31845 Rev. 3 - 2 1 of 17 www.diodes.com July 2010 © Diodes Incorporated AP5726 WHITE LED STEP-UP CONVERTER Pin Descriptions Pin Name SW GND FB EN OVP VIN Description Switch Pin. Connect inductor/diode here. Minimize trace area at this pin to reduce EMI. GND pin. Feedback Pin. Reference voltage is 0.31V. Connect cathode of lowest LED and a sense resister here. Calculate resistor value according to the formula: RSET = 0.31V / ILED 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 needed, 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. Functional Block Diagram OVP 5 1 SW Comparator - Driver Q1 A2 + Rc - CONTROL LOGIC OTP A1 + Cc VREF 0.31V Σ - VIN 6 + FB 3 RAMP Generator EN 4 2 GND Enable 1.2MHz Oscillator AP5726 Document number: DS31845 Rev. 3 - 2 2 of 17 www.diodes.com July 2010 © Diodes Incorporated AP5726 WHITE LED STEP-UP CONVERTER Absolute Maximum Ratings Symbol Rating Unit 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 VIN TJ(MAX) TLEAD TST Parameter 150 300 o -65 to +150 o Maximum Junction Temperature Lead Temperature Storage Temperature Range V o C C C 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. Recommended Operating Conditions Symbol VIN TJ TA Parameter Input Voltage Operating Junction Temperature Operating Ambient Temperature AP5726 Document number: DS31845 Rev. 3 - 2 3 of 17 www.diodes.com Min 2.7 -40 -40 Max 5.5 125 85 Unit V o C o C July 2010 © Diodes Incorporated AP5726 WHITE LED STEP-UP CONVERTER Electrical Characteristics (VIN = 3.6V, TA = 25°C, unless otherwise specified.) Symbol Parameter System Supply Input VIN Operating Input Voltage UVLO Under Voltage Lockout Under Voltage Lockout Hysteresis 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 θJA θJC Notes: Conditions FB=0.41V, No Switching VEN < 0.4V Normal Operation ON OFF SOT26 (Note 2) Thermal Resistance Junction-toTSOT23-6 (Note 2) Ambient DFN2020C-6 (Note 2) SOT26 (Note 2) Thermal Resistance Junction-toTSOT23-6 (Note 2) Case DFN2020C-6 (Note 2) 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 % 0.279 10 0.31 45 0.341 100 V nA - 0.95 750 1.2 - Ω mA 1.5 26 4 30 162 152 200 36 32 30 0.4 6 34 V V μA V o C/W o C/W 2. Test condition for SOT26, TSOT23-6 and DFN2020C-6: Device mounted on FR-4 substrate, single-layer PC board, 2oz copper, with minimum recommended pad layout AP5726 Document number: DS31845 Rev. 3 - 2 4 of 17 www.diodes.com July 2010 © Diodes Incorporated AP5726 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 3.5 1.25 5 5.5 100 1.2 95 Max Duty(%) Frequency(MHz) 4.5 VIN vs. Max Duty VIN vs. Frequency 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 VIN vs. Feedback Voltage 3 3.5 4 VIN(V) 4.5 5 5.5 IOUT vs. Feedback Voltage 0.35 0.35 Feedback Voltage(V) Feedback Voltage(V) 4 VIN (V) 0.33 0.31 0.29 0.27 0.33 0.31 0.29 0.27 0.25 0.25 2.5 3 3.5 AP5726 Document number: DS31845 Rev. 3 - 2 4 VIN (V) 4.5 5 5.5 0 10 20 30 40 50 IOUT (mA) 5 of 17 www.diodes.com July 2010 © Diodes Incorporated AP5726 WHITE LED STEP-UP CONVERTER Typical Performance Characteristics (Continued) Temperature vs. Shutdown Current V IN 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 V IN (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(V) 0.35 VIN = 4.2V 0.33 0.31 VIN = 3.6V 0.29 0.27 0.25 -50 -25 0 25 50 75 Temperature(℃ ) AP5726 Document number: DS31845 Rev. 3 - 2 100 125 6 of 17 www.diodes.com July 2010 © Diodes Incorporated AP5726 WHITE LED STEP-UP CONVERTER Typical Performance Characteristics (Continued) IOUT vs. Efficiency IOUT vs. Efficiency 90 90 V IN = 4.2V 85 80 75 Efficiency(%) Efficiency(%) 85 V IN = 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 20 IOUT (m A) 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) AP5726 Document number: DS31845 Rev. 3 - 2 7 of 17 www.diodes.com July 2010 © Diodes Incorporated AP5726 WHITE LED STEP-UP CONVERTER Typical Performance Characteristics (Continued) VOUT Ripple VIN = 3.6V; 6 LEDs ; IOUT = 30mA VOUT Ripple VIN = 3.6V; 4 LEDs ; IOUT = 30mA SW SW VOUT VOUT POWER OFF VIN = 3.6V; 6 LEDs ; IOUT = 30mA POWER ON VIN = 3.6V; 6 LEDs ; IOUT = 30mA AP5726 Document number: DS31845 Rev. 3 - 2 VEN VEN VOUT VOUT Irushi Irushin g 8 of 17 www.diodes.com July 2010 © Diodes Incorporated AP5726 WHITE LED STEP-UP CONVERTER Applications Information Inductor Selection A 10μH~22μH inductor is recommended for most AP5726 applications. For high efficiency the inductor should have low core losses at 1.2MHz and low DCR (copper wire resistance). The inductor saturation current rating should also exceed the peak input current, especially for high load current applications (like 3S8P). Capacitor Selection The small size of ceramic capacitors are ideal for AP5726 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 AP5726 applications. For high output current applications like 3S8P, larger output capacitor of 2.2uF ~ 4.7uF is recommended to minimize output ripple. Diode Selection Schottky diodes, with their low forward voltage drop and fast reverse recovery, are the ideal choices for AP5726 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. Larger Schottky diode capacitance can cause significant switching losses at the 1.2MHz switching frequency of the AP5726. A Schottky diode rated at 100mA to 200mA is sufficient for most AP5726 applications. LED Current Control The LED current is controlled by the feedback resistor (RSET in Figure 1). The feedback reference is 0.31V. The LED current is 0.31V/ 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 = 0.31V/ILED (See Table 1) Table 1. RSET Resistor Value Selection ILED (mA) RSET (Ω) 5 62 10 31 15 20.6 20 15.5 30 10.3 AP5726 Document number: DS31845 Rev. 3 - 2 9 of 17 www.diodes.com July 2010 © Diodes Incorporated AP5726 WHITE LED STEP-UP CONVERTER Applications 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 AP5726 will then switch at a high duty cycle resulting in a high output voltage, which may cause the SW and OVP pin voltage to exceed the voltage rating of these pins. The OVP pin monitors the output voltage. If the output voltage reaches the over voltage protection threshold at the OVP pin (Figure 2), the over voltage protection is activated and SW pin stops switching. L1 22uH VIN D1 COUT 1uF C IN 1uF V IN SW x AP5726 OVP EN x FB RSET 15 GND 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 AP5726 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 AP5726 and corresponds to zero LED current. A 100% duty cycle corresponds to full current. The typical frequency range of the PWM signal is below 2kHz. AP5726 Document number: DS31845 Rev. 3 - 2 10 of 17 www.diodes.com July 2010 © Diodes Incorporated AP5726 WHITE LED STEP-UP CONVERTER Applications 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. AP5726 FB VDC R3 100k R2 5k RSET 15 Figure 3. Dimming Control Using a DC Voltage 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. 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. AP5726 FB RINC Logic Signal RSET Figure 4. Dimming Control Using a Logic Signal AP5726 Document number: DS31845 Rev. 3 - 2 11 of 17 www.diodes.com July 2010 © Diodes Incorporated AP5726 WHITE LED STEP-UP CONVERTER Applications Information (Continued) VOUT VIN L1 C1 1uF D2 D1 22uH B0540WS LED C2 1uF U1 1 2 D3 R1 15ohm LED 3 Vin SW GND OVP FB EN 6 5 4 ON OFF AP5726 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 AP5726 Document number: DS31845 Rev. 3 - 2 12 of 17 www.diodes.com July 2010 © Diodes Incorporated AP5726 WHITE LED STEP-UP CONVERTER Ordering Information AP 5726 XXX G - 7 Device AP5726WG-7 AP5726WUG-7 AP5726FDCG-7 Notes: Package Green W : SOT26 WU : TSOT23-6 FDC : DFN2020C-6 G : Green Package Code W WU FDC Packing 7 : Tape & Reel 7” Tape and Reel Quantity Part Number Suffix 3000/Tape & Reel -7 3000/Tape & Reel -7 3000/Tape & Reel -7 Packaging (Note 3) SOT26 TSOT23-6 DFN2020C-6 3. 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. Marking Information (1) SOT26 and TSOT23-6 ( Top View ) 5 4 7 6 XX Y W X 1 2 3 Part Number AP5726WG-7 AP5726WUG-7 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 SOT26 TSOT23-6 Identification Code FD GD (2) DFN2020C-6 ( Top View ) XX YWX Part Number AP5726FDCG-7 AP5726 Document number: DS31845 Rev. 3 - 2 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 17 www.diodes.com Identification Code GD July 2010 © Diodes Incorporated AP5726 WHITE LED STEP-UP CONVERTER Package Outline Dimensions (All Dimensions in mm) (1) Package Type: SOT26 (2) Package Type: TSOT23-6 AP5726 Document number: DS31845 Rev. 3 - 2 14 of 17 www.diodes.com July 2010 © Diodes Incorporated AP5726 WHITE LED STEP-UP CONVERTER Package Outline Dimensions (Continued) 0.43mon. 0.57/0.63 (3) 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 Top View 0.37 A 2x- 0.9 0.45 0.25/0.35 0.86/1.06 1.95/2.075 R0. 15 1 R0. 0.65 0.25 B 0.65nom. 0.25/0.35 Bottom View AP5726 Document number: DS31845 Rev. 3 - 2 1.59 0.10 M C A B Land Pattern Recommendation (Unit:mm) 15 of 17 www.diodes.com July 2010 © Diodes Incorporated AP5726 WHITE LED STEP-UP CONVERTER Taping Orientation For 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. AP5726 Document number: DS31845 Rev. 3 - 2 16 of 17 www.diodes.com July 2010 © Diodes Incorporated AP5726 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. 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