BUCK DRIVER AP8803 step-down DC/DC converter designed drive LEDs

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BUCK DRIVER AP8803 step-down DC/DC converter designed drive LEDs

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AP8803
BUCK DRIVER
AP8803 step-down DC/DC converter designed drive LEDs with constant current. device drive LEDs, depending forward voltage LEDs, series from voltage source 30V. Series connection LEDs provides identical currents resulting uniform brightness eliminating need ballast resistors. AP8803 switches frequency 700kHz. This allows small size external components, hence minimizing area needed.
Assignments
TSOT23-5
CTRL View
PRODUCT
Maximum output current AP8803 external resistor connected between input pins. Dimming achieved applying either voltage signal CTRL input pin. input voltage 0.2V lower CTRL shuts down output puts device into low-current standby state.
Features
driving current High efficiency Operating input voltage High switching frequency 700kHz PWM/DC input dimming control Built-in output open-circuit protection TSOT23-5 available "Green" Mold Compound lead Free Finish/RoHS Compliant (Note
Directive 2002/95/EC (RoHS). applicable RoHS exemptions applied. Please visit website
Notes:
Typical Application Circuit
12V_DC CTRL AP8803 RSET
Figure Typical Application Circuit
AP8803
Document number: DS31970 Rev.
www.diodes.com
September 2009
Diodes Incorporated
AP8803
BUCK DRIVER Descriptions
Name Description Switch Pin. Connect inductor/freewheeling diode here, minimizing track length this reduce EMI. Nominal Output Current Pin. Configure output current device. Dimming On/Off Control Input. Leave floating normal operation. (VCTRL VREF 1.25V giving nominal average output current IOUTnom 0.1/RS) Drive voltage below 0.2V turn output current Drive with voltage (0.3V VCTRL 1.25V) adjust output current from 100% IOUTnom Input voltage 0.2V lower forces device into current standby mode shuts output. signal allows output current adjusted above below level resistor connected input pin. Input Supply Pin. Must locally decoupled with 2.2µF ceramic capacitor.
CTRL
PRODUCT
Absolute Maximum Ratings
Symbol VCTRL TLEAD Parameter Continuous voltage Transient 0.5s) voltage Transient 0.5s) CTRL input voltage Switch current Junction Temperature Lead Temperature Soldering Storage Temperature Range Rating -0.3~30 -0.3~30 -0.3 1.25 +150 Unit
Caution: absolute maximum ratings rated values exceeding which product could suffer physical damage. These values must therefore exceeded under condition. Semiconductor devices sensitive damaged exposure events. Suitable precautions should taken when handling transporting these devices
Recommended Operating Conditions
Symbol VCTRLH VCTRLL Parameter Operating Input Voltage Voltage High Voltage Ambient Temperature Range 0.25 Unit
AP8803
Document number: DS31970 Rev.
www.diodes.com
September 2009
Diodes Incorporated
AP8803
BUCK DRIVER Electrical Characteristics (VIN 12V, 25°C, unless otherwise specified.)
Symbol VINSU VINSD VTHD ISET VREF RDS(on) Parameter Internal regulator start threshold Internal regulator shutdown threshold Quiescent Current Internal Threshold Voltage input current Internal Reference Voltage Resistance MOSFET Continuous switch current Switch leakage current Switching Frequency Thermal Resistance Junction-toAmbient Conditions rising falling CTRL floating 250kHz VSET VIN-0.1 (Note Typ. 5.65 5.55 1.25 1.25 Unit °C/W
PRODUCT
ISW_Leakage fOSC
Notes:
TSOT23-5 (Note
Refer figure device derating curve. Test condition SOT23-5: Device mounted FR-4 PCB, 2"x2", copper, minimum recommended layout layer thermal vias bottom layer ground plane. better thermal performance, larger copper heat-sink needed.
Applications Information
Current Control current controlled resistor RSET Figure Connected between nominal average output current LED(s) defined
VTHD RSET
CTRL driven external voltage (lower than 2.5V), average current
ILED
VCTRL VTHD VREF RSET
graph figure gives values nominal average output current several values current setting resistor (RSET) typical application circuit shown Figure different voltages applied CTRL pin. used determine RSET value based desired current condition CTRL (floating driven with external voltage lower than 2.5V higher than 0.2V).
AP8803
Document number: DS31970 Rev.
www.diodes.com
September 2009
Diodes Incorporated
AP8803
BUCK DRIVER
current Versus RSET VCTRL
1200
1000 Current [mA]
current VCTRL 1.25V current VCTRL 2.5V 0.39 0.47 0.75 0.82 0.47 0.75 0.82 current VCTRL 0.625V
PRODUCT
0.15
0.15 0.45 0.75 1.05 1.35 1.65 1.95 2.25 2.55 2.85 RSET value [Ohms]
Figure Current setting RSET VCTRL
Inductor Selection inductor higher) recommended most AP8803 applications with input voltage 24V. Figure displays resulting switching frequency varying main circuit parameters: Supply voltage, inductor value number LEDs driven. particular, graph figure gives values nominal switching frequency several values inductors (L1) typical application circuit shown Figure different input voltages load condition. used determine inductor value based desired switching frequency input load conditions.
Switching Frequency ILED=1A
LEDs LEDs
Frequency [kHz]
Inductor Value [uH]
Figure Switching Frequency Supply voltage, Inductor, number LEDs
AP8803
Document number: DS31970 Rev.
www.diodes.com
September 2009
Diodes Incorporated
AP8803
BUCK DRIVER
Capacitor Selection small size ceramic capacitors makes them ideal AP8803 applications. types recommended because they retain their capacitance over wider voltage temperature ranges than other types such Z5U. 2.2F input capacitor sufficient most intended applications AP8803. Diode Selection Schottky diodes, e.g. B240 DFLS240L proprietary PowerDI®123 package, with their forward voltage drop fast reverse recovery, ideal choice AP8803 applications. addition, Super Barrier Rectifier devices SBR2A40P1) used their enhanced thermal performances.
PRODUCT
Dimming Pulse Width Modulated (PWM) signal with resolution 8bit, applied CTRL change output current value above below nominal average value resistor RSET. achieve this resolution frequency lower than 500Hz. recommended method driving CTRL controlling amplitude waveform small switching transistor shown below: Thermal Considerations graph below figure gives details power derating. This assumes device mounted 25x25mm with copper standing still air.
This scheme uses 200k resistor between CTRL internal voltage reference pull-up resistor external transistor MMBT3904.
Thermal Considerations
graph below figure gives details power derating. This assumes device mounted 25x25mm with copper standing still air.
AP8803
Document number: DS31970 Rev.
www.diodes.com
September 2009
Diodes Incorporated
AP8803
BUCK DRIVER
Maximum Power Diss ipation
Power
SOT23-5
PRODUCT
Ambient Temperature (Deg
Figure Derating curve
Ordering Information Device
AP8803-WTG-7
Package Code
Packaging (Note
TSOT23-5
7"/13" Tape Reel Quantity Part Number Suffix
3000/Tape Reel
Marking Information
Identification Code Year Week: A~Z: 1~26 week a~z: 27~52 week; represents week A~Z: Green
AP8803
Document number: DS31970 Rev.
www.diodes.com
September 2009
Diodes Incorporated
AP8803
BUCK DRIVER
Package Outline Dimensions
PRODUCT
AP8803
Document number: DS31970 Rev.
www.diodes.com
September 2009
Diodes Incorporated
AP8803
BUCK DRIVER
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PRODUCT
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AP8803
Document number: DS31970 Rev.
www.diodes.com
September 2009
Diodes Incorporated

BUCK DRIVER AP8803 step-down DC/DC converter designed drive LEDs

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