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DIODES INC AP8803 handbook

1. DIODES N C O R PORATED Description The AP8803 is a step down DC DC converter designed to drive LEDs with a constant current The device can drive up to 7 LEDs depending on the forward voltage of the LEDs in series from a voltage source of 8V to 30V Series connection of the LEDs provides identical LED currents resulting in uniform brightness and eliminating the need for ballast resistors The AP8803 switches at frequency up to 700kHz This allows the use of small size external components hence minimizing the PCB area needed Maximum output current of AP8803 is set via an external resistor connected between the Viy and SET input pins Dimming is achieved by applying either a DC voltage ora PWM signal at the CTRL input pin An input voltage of 0 2V or lower at CTRL shuts down the output at SW and puts the device into a low current standby state Features e LED driving current up to 1A High efficiency up to 92 e Operating input voltage up to 30V e High switching frequency up to 700kHz PWM DC input for dimming control Built in output open circuit protection e TSOT23 5 is available in Green Mold Compound No Br Sb and lead Free Finish ROHS Compliant Note 1 Notes 1 http www diodes com products lead_free html Typical Application Circuit 12V_DC AP8803 30V 3W BUCK LED DRIVER Pin Assignments TSOT23 5 SW 1 5 Vin GND 2 CTRL 3 4 SET Top View EU Directive 2002 95 EC RoHS All appli
2. ac jae Lu Note Controlling dimensions are in millimeters Approximate dimensions are provided in inches AP8803 7 of 8 December 2009 Document number DS31970 Rev 3 www diodes com Diodes Incorporated AP8803 DIODES 30V 3W BUCK LED DRIVER N Cc O R P GORA TE D IMPORTANT NOTICE DIODES INCORPORATED MAKES NO WARRANTY OF ANY KIND EXPRESS OR IMPLIED WITH REGARDING 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 Shoul
3. t 30V 5 LEDs 200 100 o l r r l o 50 100 150 200 250 300 350 400 450 500 Inductor Value uH Figure 3 Switching Frequency vs Supply voltage Inductor and number of LEDs AP8803 4of8 December 2009 Document number DS31970 Rev 3 www diodes com Diodes Incorporated AP8803 DIODES 30V 3W BUCK LED DRIVER N C O R P OF R ATE OD Capacitor Selection The small size of ceramic capacitors makes them ideal for AP8803 applications X5R and X7R types are recommended because they retain their capacitance over wider voltage and temperature ranges than other types such as Z5U A 2 2uF input capacitor is sufficient for most intended applications of AP8803 Diode Selection Schottky diodes e g B240 or DFLS240L in the proprietary PowerDI 123 package with their low forward voltage drop and fast reverse recovery are the ideal choice for AP8803 applications In addition Super Barrier Rectifier devices as SBR2A40P1 can be used for their enhanced thermal performances PWM Dimming A Pulse Width Modulated PWM signal with a max resolution of 8bit can be applied to the CTRL pin to change the output current to a value above or below the nominal average value set by resistor Rser To achieve this resolution the PWM frequency has to be lower than 500Hz The recommended method of driving the CTRL pin and controlling the amplitude of the PWM waveform is to use a small NPN switching transistor as shown be
4. 6 V Isw Switch current 1 25 A Ts Junction Temperature 150 C TLeEAD Lead Temperature Soldering 300 C Tst Storage Temperature Range 65 to 150 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 Semiconductor devices are ESD sensitive and may be damaged by exposure to ESD events Suitable ESD precautions should be taken when handling and transporting these devices Recommended Operating Conditions Vin Operating Input Voltage 80 3 v Veru Voltage High Pos 25 v Voltage Low Oooo S oas d yv Ta Ambient Temperature Range 40 105 Duty Cycle _ Using Inductor gt 1004H Note 3 o1 095 Notes 2 For most applications the LED current will be within 8 over the duty cycle range specified Duty cycle accuracy is also dependent on propagation delay Smaller size inductors can be used but LED current accuracy may be greater than 8 at extremes of duty cycle This is most noticeable at low duty cycles less than 0 1 or when the input voltage is high and only one LED is being driven AP8803 2of8 December 2009 Document number DS31970 Rev 3 www diodes com Diodes Incorporated AP8803 DIODES 30V 3W BUCK LED DRIVER N Cc ORPORATED Electrical Characteristics vn 12V Ta 25 C unless otherwise specified Symbol Pa
5. cable ROHS exemptions applied Please visit our website at AP8803 Figure 1 Typical Application Circuit AP8803 Document number DS31970 Rev 3 1of8 www diodes com December 2009 Diodes Incorporated AP8803 DIODES 30V 3W BUCK LED DRIVER N C O RPORATED Pin Descriptions Pin Name Description SW Switch Pin Connect inductor freewheeling diode here minimizing track length at this pin to reduce EMI GND GND pin SET Set Nominal Output Current Pin Configure the output current of the device Dimming and On Off Control Input e Leave floating for normal operation Verr Vrer 1 25V giving nominal average output current loutnom 0 1 Rs CTRL e Drive to voltage below 0 2V to turn off output current e Drive with DC voltage 0 3V lt Vctri lt 1 25V to adjust output current from 25 to 100 of loutnom e Input voltage of 0 2V or lower forces the device into low current standby mode and shuts off the output A PWM signal allows the output current to be adjusted above or below the level set by the resistor connected to SET input pin Vin Input Supply Pin Must be locally decoupled to GND with gt 2 2uF X7R ceramic capacitor Absolute Maximum Ratings Symbol Parameter Rating Unit V Continuous Vn pin voltage 0 3 30 V 5 Transient t lt 0 5s 40 v SW voltage 0 3 30 v SW Transient t lt 0 5s 40 VCTRL CTRL pin input voltage 0 3
6. d 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 ex
7. low Thermal Considerations The graph below in figure gives details for power derating This assumes the device to be mounted on a 25x25mm PCB with Loz copper standing in still air CTRL AP8803 This scheme uses the 200k resistor between the CTRL pin and the internal voltage reference as a pull up resistor for the external transistor eg MMBT3904 Thermal Considerations The graph below in figure 4 gives details for power derating This assumes the device to be mounted on a 25x25mm PCB with 10z copper standing in still air AP8803 5 of 8 December 2009 Document number DS31970 Rev 3 www diodes com Diodes Incorporated AP8803 DIODES 30V 3W BUCK LED DRIVER N C O R PORATED Maximum Power Dissipation 1 2 0 25 50 75 100 125 150 Ambient Temperature Deg C D E PRODUCT Figure 4 Derating curve Ordering Information Device Package Packaging 7 13 Tape and Reel Code Note 2 Quantity Part Number Suffix E AP8803WTG 7 WT TSOT23 5 3000 Tape amp Reel 7 Marking Information AY Identification Code Y Year 0 9 W Week A Z 1 26 week a z 27 52 week z represents 52 and 53 week AP8803 6of8 December 2009 Document number DS31970 Rev 3 www diodes com Diodes Incorporated AP8803 3 _ aancmone 30V 3W BUCK LED DRIVER I N COR P ORATEO Package Outline Dimensions e O O
8. pertise 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 AP8803 8 of 8 December 2009 Document number DS31970 Rev 3 www diodes com Diodes Incorporated
9. rameter Conditions Min Typ Max Unit Vinsu Internal regulator start up threshold Vin rising 5 65 V Internal regulator shutdown Vin fallin Vins fthreshold j i 3 99 X lo Quiescent Current CTRL pin floating f 250kHz 1 8 5 mA V HD Internal Threshold Voltage 92 100 108 mV Iset SET pin input current Vset Vin 0 1 1 25 10 uA VREF Internal Reference Voltage 1 25 V Ros on On Resistance of MOSFET Isw 1A 0 5 1 Q Isw Continuous switch current Note 3 1 A Isw_Leakage_ Switch leakage current 8 yA fosc Switching Frequency 0 7 MHz Ora Hen Resistance Junction to TSOT23 5 Note 4 125 C W Notes 3 Refer to figure 7 for the device derating curve 4 Test condition for SOT23 5 Device mounted on FR 4 PCB 2 x2 20z copper minimum recommended pad layout on top layer and thermal vias to bottom layer ground plane For better thermal performance larger copper pad for heat sink is needed Applications Information LED Current Control The LED current is controlled by the resistor Rser in Figure 1 Connected between Vij and SET the nominal average output current in the LED s is defined as Vrap Rser hep If the CTRL pin is driven by an external voltage lower than 2 5V the average LED current is Verret Vip I LED Veer Rser The graph in figure 2 gives values of nominal average output current for several values of current setting resistor RSET in the typical application circuit shown on Figure 1 for different voltage
10. s applied on the CTRL pin It can be used to determine the RSET value based on the desired LED current and the condition of the CTRL pin floating or driven with an external DC voltage lower than 2 5V and higher than 0 2V AP8803 3of8 December 2009 Document number DS31970 Rev 3 www diodes com Diodes Incorporated m aa a AP838803 DIODES 30V 3W BUCK LED DRIVER N C O R PORATED LED current Versus RSET and VCTRL e LED current VCTRL 1 25V s LED current VCTRL 2 5V LED current VCTRL 0 625V LED Current mA 0 015 03 045 06 075 09 105 12 135 15 165 18 19 21 225 24 255 27 285 3 RSET value Ohms Figure 2 LED Current setting Vs Rset and Vctrt Inductor Selection A 33HH inductor or higher is recommended for most AP8803 applications with input voltage at 24V Figure 3 displays the resulting switching frequency varying the main circuit parameters Supply voltage inductor value and number of LEDs to be driven In particular the graph in figure 3 gives values of nominal switching frequency for several values of inductors L1 in the typical application circuit shown on Figure 1 for different input voltages and load condition It can be used to determine the inductor value based on the desired switching frequency and the input and load conditions Switching Frequency ILe gt 1A e 12V 1 LED E 24V 3 LEDs

DIODES INC AP8803 handbook

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