AP8800 350mA LED Step-down Converter General Description Features • • • • • • • • • LED driving current up to 350mA Compatible with 12V & 24V standard systems High efficiency up to 92% High switching frequency up to 0.6MHz PWM/DC input for dimming control Built-in soft-start function Built-in output open-circuit protection SOP-8L, MSOP-8L and DFN3030-10 are available in “Green” Molding Compound (No Br, Sb) Lead Free Finish/RoHS Compliant (Note 1) The AP8800 is a step-down DC/DC converter designed to drive LEDs with a constant current. The device can drive up to seven LEDs, depending on the forward voltage of the LEDs, in series from a voltage source of 8V to 28V. Series connection of the LEDs provides identical LED currents resulting in uniform brightness and eliminates the need for ballast resistors. The AP8800 switches at frequency up to 0.6MHz. This allows the use of small size external components, hence minimizing the PCB area needed. Maximum output current of AP8800 is set via an external resistor connected between the VIN and SET input pins. Dimming is achieved by applying either a DC voltage or a 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. Applications • • • • Commercial & Industrial lighting Small LCD panel backlight Architecture Detail lighting Appliances interior lighting Typical Application Circuit Figure 1: Typical Application Circuit AP8800 Rev. 4 DS31764 1 of 13 www.diodes.com DECEMBER 2009 © Diodes Incorporated AP8800 350mA LED Step-down Converter Ordering Information AP 8800 XX G - X Package S : SOP-8L M8 : MSOP-8L FN : DFN3030-10 Device AP8800SG-13 AP8800M8G-13 AP8800FNG-7 Notes: Green Packing G : Green 7/ 13 : Tape & Reel Package Code Packaging (Note 2) S M8 FN SOP-8L MSOP-8L DFN3030-10 7”/13” Tape and Reel Quantity Part Number Suffix 2500/Tape & Reel 2500/Tape & Reel 3000/Tape & Reel -13 -13 -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. AP8800 Rev. 4 DS31764 2 of 13 www.diodes.com DECEMBER 2009 © Diodes Incorporated AP8800 350mA LED Step-down Converter Pin Assignments (1) SOP-8L (2) MSOP-8L ( Top View ) CTRL 1 2 RSVD SW AP8800 3 GND 4 ( Top View ) 8 SET CTRL 1 7 NC 6 5 NC RSVD SW VIN 2 3 GND 4 AP8800 8 SET 7 NC 6 5 NC VIN (3) DFN3030-10 ( Top View ) CTRL 1 10 SET RSVD 2 9 NC NC 3 8 NC SW 4 7 NC GND 5 6 VIN AP8800 Pin Descriptions Pin Name SW Description Switch Pin. Connect inductor/freewheeling diode here. Minimize trace area at this pin to reduce EMI. GND GND pin SET Set Nominal Output Current Pin. To configure the output current of the device. CTRL VIN RSVD NC AP8800 Rev. 4 DS31764 Dimming and On/Off Control Input. 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. The input impedance is about 200kΩ, and if the pin is left open VCTRL = VREF Input Supply Pin. Must be locally bypassed. Reserved. Normally connected to Ground No Connection. 3 of 13 www.diodes.com DECEMBER 2009 © Diodes Incorporated AP8800 350mA LED Step-down Converter Block Diagram SET SW VIN Voltage Regulator 5V Comparator PWM/DC Control CTRL Sensing Block AP8800 VREF 1.25V R GND Figure 2: AP8800 Block Diagram Absolute Maximum Ratings Symbol Parameter Rating Unit V VIN VIN pin voltage -0.3~30 VSW SW voltage -0.3~30 TJ C 300 o C -65 to +125 o C Maximum Lead Temperature TST Caution: 125 Maximum Junction Temperature TLEAD Storage Temperature Range V o 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 Symbol Parameter TA Ambient Temperature Range Duty Cycle Using Inductor ≥ 100µH (Note 3) Notes: Min -40 0.1 Max 85 0.95 Unit ºC 3. 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. AP8800 Rev. 4 DS31764 4 of 13 www.diodes.com DECEMBER 2009 © Diodes Incorporated AP8800 350mA LED Step-down Converter Electrical Characteristics Symbol VIN IOUT IQ FOSC VTHD VREF SET Rds(on) EN EN Parameter Operating Input Voltage Continuous switch Current Quiescient Current Switching Frequency Internal Threshold Voltage Internal Reference Voltage SET pin input current On Resistance of MOSFET Switch leakage current Voltage High Voltage Low θJA Thermal Resistance Junction-to-Ambient θJC Thermal Resistance Junction-to-Case ISW Leakage Notes: (VIN =12V, TA=25oC, unless otherwise specified) Conditions VSET=VIN-0.1 Min 8.0 92 - ON OFF SOP-8L (Note 5) MSOP-8L (Note 5) DFN3030-10 (Note 5) SOP-8L (Note 5) MSOP-8L (Note 5) DFN3030-10 (Note 5) 1.25 - (Note 4) Typ. 20 0.25 100 1.25 1.3 1.7 92 120 46 60 98 32 Max 28 350 30 108 2.2 5 0.2 - Unit V mA μA MHz mV V μA Ω μA V V °C/W °C/W °C/W °C/W °C/W °C/W 4. Refer to figure 5 for the device derating curve. 5. Test condition for SOP-8L, MSOP-8L and DFN3030-10: Device mounted on FR-4 PCB, 2”x2”, 2oz 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. Application Information AP8800 Rev. 4 DS31764 5 of 13 www.diodes.com DECEMBER 2009 © Diodes Incorporated AP8800 350mA LED Step-down Converter LED Current Control The LED current is controlled by the resistor RSET in Figure 1. If the CTRL pin is floating and at a nominal voltage of VREF, the external current sense resistor RSET (greater than 0.3 Ω) is connected between VIN and SET and defines the nominal average output current in the LED(s) as: VTHD RSET ILED = If the CTRL pin is driven by an external voltage (lower than 2.5V), the average LED current in this case is: ILED = VCTRL VTHD VREF RSET The graph in figure 3 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 voltages applied on the CTRL pin. LED current Versus RSET and VCTRL 400 0.56 350 0.3 0.33 LED Current [mA] 300 0.39 250 0.47 200 0.3 150 50 LED current @ VCTRL = 2.5V 1 0.56 0.68 0.39 0.47 0.56 100 LED current @ VCTRL = 1.25V 0.68 0.75 0.82 1.2 0.82 0.68 1 1.2 0.82 LED current @ VCTRL = 0.625V 1.5 1 1.2 2 1.5 1.5 2 3 2 3 3 0 0 0.15 0.3 0.45 0.6 0.75 0.9 1.05 1.2 1.35 1.5 1.65 1.8 1.95 2.1 2.25 2.4 2.55 2.7 2.85 3 RSET value [Ohms] Figure 3: LED Current setting Vs RSET and VCTRL AP8800 Rev. 4 DS31764 6 of 13 www.diodes.com DECEMBER 2009 © Diodes Incorporated AP8800 350mA LED Step-down Converter Application Information (Continued) Switching Frequency 700 600 100 47 Frequency [kHz] 500 150 400 12V - 1LED 68 24V - 3 LEDs 220 300 28V - 4LEDs 100 200 150 470 220 100 470 0 0 50 100 150 200 250 300 350 400 450 500 Inductor Value [uH] Figure 4: Switching Frequency Vs Supply voltage, Inductor, and number of LEDs Capacitor Selection The small size of ceramic capacitors makes them ideal for AP8800 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 1μF input capacitor is sufficient for most intended applications of AP8800. Diode Selection Schottky diode, e.g. B140, with their low forward voltage drop and fast reverse recovery, is the ideal choice for AP8800 applications. PWM Dimming A Pulse Width Modulated (PWM) signal with a max resolution of 8bit can be applied to the CTRL pin to regulate the output current to a value above or below the nominal average value set by resistor RSET. Miscellaneous To ensure optimal performance, RSVD pin should be connected to the GND pin with the shortest trace length AP8800 Rev. 4 DS31764 7 of 13 www.diodes.com DECEMBER 2009 © Diodes Incorporated AP8800 350mA LED Step-down Converter Application Information (Continued) Inductor Selection A 100μH inductor is recommended for most AP8800 applications with input voltage at 24V. Figure 4 displays the resulting switching frequency varying the main circuit parameters: Supply voltage, Inductor value and number of LEDs to be driven. Thermal Considerations The graph below in figure 5, gives details for power derating. This assumes the device to be mounted on a 25x25mm PCB with 1oz copper standing in still air. Maximum Power Dissipation 2 1.8 1.6 DFN3030-10 1.4 Power (W) 1.2 1 0.8 SOP8L 0.6 0.4 MSOP8L 0.2 0 0 25 50 75 100 125 150 Ambient Temperature (Deg C) Figure 5: Derating curve AP8800 Rev. 4 DS31764 8 of 13 www.diodes.com DECEMBER 2009 © Diodes Incorporated AP8800 350mA LED Step-down Converter Marking Information (1) SOP-8L ( Top View ) 5 8 Logo Part Number G : Green YY : Year : 08, 09,10~ WW : Week : 01~52; 52 represents 52 and 53 week X : Internal Code AP8800 YY WW X X 1 4 (2) MSOP-8L ( Top View ) 8 7 Logo 6 5 YWX Part Number AP8800 1 2 3 A~Z : Green Y : Year : 0~9 W : Week : A~Z : 1~26 week; a~z : 27~52 week; z represents 52 and 53 week 4 (3) DFN3030-10 ( Top View ) XX YW X Part Number AP8800FNG-7 AP8800 Rev. 4 DS31764 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 DFN3030-10 9 of 13 www.diodes.com Identification Code A4 DECEMBER 2009 © Diodes Incorporated AP8800 350mA LED Step-down Converter Package Information (All Dimensions in mm) 0.254 0.10/0.20 3.85/3.95 5.90/6.10 (1) Package Type: SOP-8L Gauge Plane Seating Plane 0.62/0.82 Detail "A" 7°~9° 7°~9° 0.15/0.25 1.75max. 1.30/1.50 0.35max. 45° Detail "A" 0°/8° 0.3/0.5 1.27typ 4.85/4.95 5.4 8x-0.60 8x-1.55 6x-1.27 Land Pattern Recommendation (Unit: mm) (2) Package Type: MSOP-8L 4.4 4.7/5.1 2.9/3.1 8x-0.45 8x-1.4 6x-0.65 0.25 0.4/0.8 DETAIL "A" AP8800 Rev. 4 DS31764 0.95Ref. ° Gauge plane 0°/8 0.75/0.95 Land Pattern Recommendation (Unit:mm) "A" 0.05/0.15 0.05 2.9/3.1 0/0.15 0.22/0.38 0.15Typ. 1 0.65Bsc. 10 of 13 www.diodes.com DECEMBER 2009 © Diodes Incorporated AP8800 350mA LED Step-down Converter Package Information (Continued) (3) Package Type: DFN3030-10 0.15Typ. 0/0.05 Seating Plane Side View 2X- 0.25 A 0.08 C 0.57/0.60 TOP MARK 0.10 C C 2.9/3.1 2.3/2.5 B A R0 .30 0 0.25/0.55 2.9/3.1 1.5/1.7 (Pin #1 ID) 2X- 0.25 B 0.375Typ. 0.50Typ. 0.2/0.3 0.10 C A B Bottom View AP8800 Rev. 4 DS31764 11 of 13 www.diodes.com DECEMBER 2009 © Diodes Incorporated AP8800 350mA LED Step-down Converter Taping Orientation (Note 6) For DFN3030-10 Notes: 6. The taping orientation of the other package type can be found on our website at http://www.diodes.com/datasheets/ap02007.pdf. AP8800 Rev. 4 DS31764 12 of 13 www.diodes.com DECEMBER 2009 © Diodes Incorporated AP8800 350mA LED Step-down Converter 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. 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