AP8802H 60V 1A LED STEP-DOWN CONVERTER Description Pin Assignments The AP8802H is a step-down DC/DC converter designed to drive (Top View) LEDs with a constant current. The device can drive up to thirteen LEDs, depending on the forward voltage of the LEDs, in series from SET 1 a voltage source of 8V to 60V. Series connection of the LEDs 8 CTRL 7 GND GND 2 provides identical LED currents resulting in uniform brightness and eliminating the need for ballast resistors. The AP8802H switches at NC 3 frequency up to 700kHz. This allows the use of small size external VIN components, hence minimizing the PCB area needed. AP8802H 4 6 SW 5 SW PRODUCT NEW PRELIMINARY Maximum output current of AP8802H is set via an external resistor connected between the VIN and SET input pins. Dimming is SO-8EP 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 Applications standby state. Features • Commercial & industrial lighting • Small LCD panel backlight • LED driving current up to 1A • Appliances interior lighting • High efficiency up to 95% • Architecture Detail lighting • Operating input voltage up to 60V • 5% nominal accuracy • High switching frequency up to 700kHz • PWM/DC input for dimming control • Built-in output open-circuit protection • SO-8EP is available in “Green” Molding Compound (No Br, Sb) Totally Lead-Free & Fully RoHS Compliant (Notes 1 & 2) Halogen and Antimony Free. “Green” Device (Note 3) Notes: 1. No purposely added lead. Fully EU Directive 2002/95/EC (RoHS) & 2011/65/EU (RoHS 2) compliant. 2. See http://www.diodes.com for more information about Diodes Incorporated’s definitions of Halogen- and Antimony-free, "Green" and Lead-free. 3. Halogen- and Antimony-free "Green” products are defined as those which contain <900ppm bromine, <900ppm chlorine (<1500ppm total Br + Cl) and <1000ppm antimony compounds. Typical Application Circuit RSET 48V VIN 0.33 SET CTRL AP8802H C1 2.2µF AP8802H Document number: DS32227 Rev. 7 - 2 GND D1 PDS3200 L1 68µF SW 1 of 14 www.diodes.com July 2015 © Diodes Incorporated AP8802H 60V 1A LED STEP-DOWN CONVERTER Pin Descriptions Pin Name SW Function 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. PRODUCT NEW PRELIMINARY Dual function dimming control pin with an input impedance approximately 50kΩ. Input voltage of 0.2V or lower forces the device into low current standby mode and shuts off the output. A PWM signal (driven by an open-drain/collector source) allows the output current to be adjusted over a wide range up to 100%. An analog voltage between 0.3V and 2.5V adjusts the output current between 24% and 200% of the current set by 0.2V/RS. CTRL If the CTRL pin is left open then its voltage will default to VREF VIN Input Supply Pin. Must be locally bypassed. EP Exposed pad: Internally connected to IC substrate. It should be connected to GND and as large as possible thermal mass for improved thermal impedance and power dissipation capability. See Land Pad diagrams. NC No connection Functional Block Diagram Figure. 1 Functional Block Diagram AP8802H Document number: DS32227 Rev. 7 - 2 2 of 14 www.diodes.com July 2015 © Diodes Incorporated AP8802H 60V 1A LED STEP-DOWN CONVERTER Absolute Maximum Ratings (Note 4) Symbol Rating Unit VIN VIN pin Voltage -0.3 to +65 V VSW SW Voltage -0.3 to +65 V V PRODUCT NEW PRELIMINARY VCTRL Parameter CTRL Pin Input Voltage -0.3 to +6 VSENSE SET Voltage (Note 5) +0.3 to -5 V TJ Junction Temperature 150 °C TLEAD Lead Temperature Soldering 300 °C TST Storage Temperature Range -65 to +150 °C Note: 4 All voltages unless otherwise stated are measured with respect to GND. 5. VSENSE is measured with respect to VIN. Caution: Stresses greater than the 'Absolute Maximum Ratings' specified above, may cause permanent damage to the device. These are stress ratings only; functional operation of the device at conditions between maximum recommended operating conditions and absolute maximum ratings is not implied. Device reliability may be affected by exposure to absolute maximum rating conditions for extended periods of time. 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 VIN VCTRLDC VCTRLL fOSC TA Duty Cycle Notes: Min Max Unit Operating Input Voltage relative to GND Parameter 8.0 60.0 V Voltage range for 24% to 200% DC dimming relative to GND (Note 6) 0.3 2.5 V Voltage Low for PWM dimming relative to GND 0 0.2 V Maximum Switching Frequency (Note 7) — 625 kHz Ambient Temperature Range -40 +125 °C Using Inductor ≥ 100µH (Note 8) 0.10 0.95 — 6. For 100% brightness either leave floating or connect to 1.25V relative to GND. 7. AP8802H will operate at higher frequencies but accuracy will be affected due to propagation delays. 8. For most applications the LED current will be within 5% 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. Electrical Characteristics (VIN = 12V, TA = +25°C, unless otherwise specified.) Symbol IOUT IQ Parameter Continuous switch current Quiescent Current VTHD Internal Threshold Voltage VSENSEHYS Sense threshold hysteresis SET SET pin input current VREF Internal Reference Voltage RDS(ON) On Resistance of MOSFET ISW_LEAKAGE Notes: Conditions (Note 9) VSET = VIN -0.2 ISW = 0.8A Switch leakage current Min Typ Max Unit — — 1 A - 75 120 μA 190 200 210 mV — 15 — % — 5 — μA — 1.25 — V — 0.65 1.10 Ω — - 8 μA θJA Thermal Resistance Junction-to-Ambient SO-8EP (Note 10) — 45 — C/W θJC Thermal Resistance Junction-to-Case SO-8EP (Note 10) — 7 — C/W 9. Refer to figure 8 for the device derating curve. 10. Test condition for SO-8EP: 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. See Land pad diagram For better thermal performance, larger copper pad for heat-sink is needed. AP8802H Document number: DS32227 Rev. 7 - 2 3 of 14 www.diodes.com July 2015 © Diodes Incorporated AP8802H 60V 1A LED STEP-DOWN CONVERTER 0.8 1.254 0.7 CTRL VOLTAGE (V) NON-SWITCHING SUPPLY CURRENT (mA) 1.256 0.9 0.6 0.5 0.4 0.3 1.252 1.250 1.248 0.2 1.246 0.1 1.244 -40 -25 -10 5 0 0 5 10 15 20 25 30 35 40 45 50 55 60 20 35 50 65 80 95 110 125 AMBIENT TEMPERATURE (°C) Figure. 3 VCTRL vs. Ambient Temperature INPUT VOLTAGE (V) Figure. 2 Supply Current (not switching) vs. Input Voltage 1000 1.2 900 800 LED CURRENT (mA) CTRL VOLTAGE (V) 1.0 0.8 0.6 0.4 700 600 500 400 300 200 0.2 100 0 -40 -25 -10 5 0 20 35 50 65 80 95 110 125 0 1.0 1.5 2.0 RSET RESISTANCE () Figure. 5 LED Current vs. R SET 0 0.5 AMBIENT TEMPERATURE (°C) Figure. 4 RDS(ON) vs. Ambient Temperature 1200 0.5 2.5 800 RSET = 0.3 SWITCHING FREQUENCY (kHz) RSET = 0.2 1000 LED CURRENT (mA) PRODUCT NEW PRELIMINARY Typical Characteristics 800 RSET = 0.68 600 400 200 700 600 500 400 300 200 100 0 0 0 0.5 1.0 1.5 2.0 2.5 CTRL VOLTAGE (V) Figure. 6 LED Current vs. VCTRL AP8802H Document number: DS32227 Rev. 7 - 2 4 of 14 www.diodes.com 1.0 1.5 2.0 2.5 CTRL VOLTAGE (V) Figure. 7 Switching Frequency vs. V CTRL July 2015 © Diodes Incorporated AP8802H 60V 1A LED STEP-DOWN CONVERTER Typical Characteristics (TA = +25°C, VIN = 60V, L = 68µH; unless otherwise stated.) 100 8 95 6 90 4 EFFICIENCY (%) PRODUCT NEW PRELIMINARY OUTPUT CURRENT DEVIATION (%) 10 2 0 -2 -4 85 80 75 -6 70 -8 -10 6 65 12 18 24 30 36 42 48 54 60 6 500 100 450 90 400 80 350 70 DUTY CYCLE (%) SWITCHING FREQUENCY (kHz) 12 18 24 30 36 42 48 54 60 INPUT VOLTAGE (V) Figure. 9 Efficiency vs. Input Voltage INPUT VOLTAGE (V) Figure. 8 LED Current vs. Input Voltage 300 250 200 150 60 50 40 30 100 20 50 10 0 0 6 12 18 24 30 36 42 48 54 6 60 AP8802H Document number: DS32227 Rev. 7 - 2 18 24 30 36 42 48 54 60 SUPPLY VOLTAGE (V) Figure. 11 Duty Cycle vs. Input Voltage INPUT VOLTAGE (V) Figure. 10 Switching Frequency vs. Input Voltage Figure. 12 Steady State Waveforms 12 Figure. 13 Start-Up Showing LED Current Soft Start 5 of 14 www.diodes.com July 2015 © Diodes Incorporated AP8802H 60V 1A LED STEP-DOWN CONVERTER Application Information LED Current Control The LED current is controlled by the resistor RSET in Figure 14 connected between VIN and SET. The nominal average output current in the LED(s) with the CTRL pin open circuit is defined as: ILED VTHD R SET PRODUCT NEW PRELIMINARY RSET 48V 0.33 VIN SET CTRL AP8802H C1 2.2µF D1 PDS3200 L1 68µF GND SW Figure. 14 Typical Application Circuit Inductor Selection This section highlights how to select the inductor suitable for the application requirements in terms of switching frequency, LED current accuracy and temperature. 500 68 Switching Frequency @I LED = 700mA 450 12V - 3 LEDs FREQUENCY (kHz) 400 47 24V - 5 LEDs 100 48V - 10 LEDs 350 300 150 68 250 100 220 200 150 150 47 100 470 220 68 100 50 470 150 220 470 0 0 50 100 150 200 250 300 350 400 450 500 INDUCTOR VALUE (µ) Figure. 15 Switching Frequency vs. Inductor Value The inductor influences the LED current accuracy that the system is able to provide. The following section highlights how to select the inductor in relation to the device packages and the LED current, while maintaining the chip temperature below +70°C. AP8802H Document number: DS32227 Rev. 7 - 2 6 of 14 www.diodes.com July 2015 © Diodes Incorporated AP8802H 60V 1A LED STEP-DOWN CONVERTER Applications Information (cont.) 15 14 13 12 11 10 PRODUCT NEW PRELIMINARY 9 8 7 6 5 4 3 2 1 0 10 20 30 40 50 SUPPLY VOLTAGE (V) AP8802H SO-8EP Minimum Recommended Inductor Figure. 16 Recommended Inductor with 1A LED Current 60 Capacitor Selection The small size of ceramic capacitors makes them ideal for AP8802H 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 2.2μF input capacitor is sufficient for most intended applications of AP8802H. A 4.7μF input capacitor is suggested for application with an input voltage equal or higher than 60V. Diode Selection Schottky diodes, e.g. B2100 or B1100, with their low forward voltage drop and fast reverse recovery, are the ideal choice for AP8802H applications. AP8802H Document number: DS32227 Rev. 7 - 2 7 of 14 www.diodes.com July 2015 © Diodes Incorporated AP8802H 60V 1A LED STEP-DOWN CONVERTER Applications Information (cont.) LED Current Adjustment/Dimming The LED current for the AP8802H can be adjusted by driving the CTRL with a digital signal (PWM dimming) or by driving the CTRL with a DC voltage between 0.3V and 2.5V (DC dimming). If the CTRL pin is driven by an external voltage (lower than 2.5V), the average LED current is: VCTRL VTHD VREF R SET PRODUCT NEW PRELIMINARY ILED where VREF is nominally 1.25V 1200 LED Current @ 0.39 1000 VCTRL = 1.25V 0.2 LED Current @ VCTRL = 2.5V LED CURRENT (mA) 0.47 LED Current @ 800 VCTRL = 0.625V 0.56 600 0.68 0.33 0.2 0.82 0.39 0.47 400 1 1.2 0.56 0.68 0.82 0.33 1.5 1 200 1.5 0.68 0.82 0 0 0.3 2 1.2 0.47 0.6 0.9 1 1.2 1.5 3 2 2 1.2 1.5 1.8 2.1 RSET VALUE ( ) Figure. 17 LED Current vs. R 3 SET and 3 2.4 2.7 3 V CTRL Figure 17 shows that reducing the CTRL voltage by a factor of 2 also reduces the LED current by a factor of 2. The AP8802H has the ability vary the LED current by a factor of 2 above the default value set by RSET down to a factor of 0.24 of the nominal LED current. This provides an 8.33:1 dynamic range of the DC dimming. A low pass filter (pole frequency ~ 500kHz) on the CTRL pin of the AP8802H automatically provides some soft-start function of the LED current on initial start-up (this phenomenon can be seen in Figure 7); the built in soft-start period can be increased by the addition of an external capacitor onto the CTRL pin. The AP8802H’s dimming range can be increased above this DC dimming factor by applying a PWM signal to the CTRL pin using this method dimming dynamic ranges above 100 can be achieved. AP8802H Document number: DS32227 Rev. 7 - 2 8 of 14 www.diodes.com July 2015 © Diodes Incorporated AP8802H 60V 1A LED STEP-DOWN CONVERTER Applications Information (cont.) PWM Dimming of LED Current When a low frequency PWM signal with voltages between 2.5V and a low level of zero is applied to the CTRL pin the output current will be switched on and off at the PWM frequency. The resultant LED current ILEDavg will be proportional to the PWM duty cycle. See Figure 6. A Pulse Width Modulated (PWM) signal with a max resolution of 8-bit, 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 RSET. PRODUCT NEW PRELIMINARY To achieve this resolution the PWM frequency has to be lower than 500Hz. The ultimate resolution will be determined by the number of switching cycles required to get back to nominal LED current once the PWM voltage is high relative to PWM frequency. Lower switching frequencies and higher PWM frequencies will result in lower PWM dimming dynamic ranges. Figure. 18 Low Frequency PWM Operating Waveforms There are different ways of accomplishing PWM dimming of the AP8802H LED current: Directly Driving CTRL Input A Pulse Width Modulated (PWM) signal with duty cycle DPWM can be applied to the CTRL pin to adjust the output current to a value above or below the nominal average value set by resistor RSET. When driving the CTRL with a voltage waveform care should be taken not to exceed a drive voltage of 2.5V (where extra brightness is required) or 1.25V if a maximum of 100% brightness is required. A way of avoiding over-driving the CTRL pin is use an open collector/drain driver to drive the CTRL pin. Driving the CTRL Input via Open Collector Transistor The recommended method of driving the CTRL pin and controlling the amplitude of the PWM waveform is to use a small NPN switching transistor. This uses the internal pull-up resistor between the CTRL pin and the internal voltage reference to pull-up CTRL pin when the external transistor is turned off. Driving the CTRL Input From a Microcontroller If the CTRL pin is driven by a MOSFET (either discrete or open-drain output of a micro-controller) then Schottky diode maybe be required due to high Gate / Drain capacitance, which could inject a negative spike into CTRL input of the AP8802H and cause erratic operation but the addition of a Schottky clamp diode (eg Diodes Inc. SD103CWS) to ground and inclusion of a series resistor (3.3k) will prevent this. AP8802H Document number: DS32227 Rev. 7 - 2 9 of 14 www.diodes.com July 2015 © Diodes Incorporated AP8802H 60V 1A LED STEP-DOWN CONVERTER Applications Information (cont.) Soft-Start An external capacitor from the CTRL pin to ground will provide a soft-start delay, by increasing the time taken for the voltage on this pin to rise to the turn-on threshold and by slowing down the rate of rise of the control voltage at the input of the comparator. Adding capacitance increases this delay by approximately 200µs/nF. The graph below shows the variation of soft-start time for different values of capacitor. 16 PRODUCT NEW PRELIMINARY SOFT-START TIME (ms) 14 12 10 8 6 4 2 0 -2 0 20 40 60 80 100 120 CAPACITANCE (nF) Soft Start Time vs. Capacitance from ADJ Pint to Ground Thermal Considerations The graph below in Figure 19, gives details for power derating. This assumes the device to be mounted on a 25x25mm PCB with 1oz copper standing in still air. 2.5 POWER DISSIPATION (W) 2 1.5 1 0.5 0 -40 AP8802H Document number: DS32227 Rev. 7 - 2 -25 -10 5 20 35 50 65 80 AMBIENT TEMPERATURE (°C) Maximum Power Dissipation Figure. 19 AP880H Derating Curve 10 of 14 www.diodes.com 95 110 125 July 2015 © Diodes Incorporated AP8802H 60V 1A LED STEP-DOWN CONVERTER Applications Information (cont.) Fault Condition Operation The AP8802H has by default open LED protection. If the LEDs should become open circuit the AP8802H will stop oscillating; the SET pin will rise to VIN and the SW pin will then fall to GND. No excessive voltages will be seen by the AP8802H. PRODUCT NEW PRELIMINARY If the LEDs should become shorted together the AP8802H will continue to switch however the duty cycle at which it will operate will change dramatically and the switching frequency will most likely decrease. The on-time of the internal power MOSFET switch will be significantly reduced because almost all of the input voltage is now developed across the inductor. The off-time will be significantly increased because the reverse voltage across the inductor is now just the Schottky diode voltage (See Figure 20) causing a much slower decay in inductor current. During this condition the inductor current will remain within its controlled levels and so no excessive heat will be generated within the AP8802H. Fig. 20 Switching Characteristics (normal open to short LED chain) AP8802H Document number: DS32227 Rev. 7 - 2 11 of 14 www.diodes.com July 2015 © Diodes Incorporated AP8802H 60V 1A LED STEP-DOWN CONVERTER Ordering Information PRODUCT NEW PRELIMINARY AP8802H SP - 13 Device Package Code AP8802HSP-13 SP Note: Package Packing SP : SO-8EP 13 : Tape & Reel 13” Tape and Reel Packaging (Note 11) Quantity Part Number Suffix SO-8EP 2500/Tape & Reel -13 11. 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 SO-8EP ( Top View ) 8 Logo Part No. AP8802H YY WW X X E 1 AP8802H Document number: DS32227 Rev. 7 - 2 5 A~Z : Internal code YY : Year : 08, 09,10~ WW : Week : 01~52; 52 represents 52 and 53 week X : Internal Code SO-8-EP 4 12 of 14 www.diodes.com July 2015 © Diodes Incorporated AP8802H 60V 1A LED STEP-DOWN CONVERTER Package Outline Dimensions (All Dimensions in mm) SO-8EP Exposed Pad 8 5 E1 1 H 4 PRODUCT NEW PRELIMINARY F b Bottom View E 9° (All sides) N 7° A e D 45° Q C 4° ± 3° Gauge Plane Seating Plane E0 A1 L SO-8EP (SOP-8L-EP) Dim Min Max Typ A 1.40 1.50 1.45 A1 0.00 0.13 b 0.30 0.50 0.40 C 0.15 0.25 0.20 D 4.85 4.95 4.90 E 3.80 3.90 3.85 E0 3.85 3.95 3.90 E1 5.90 6.10 6.00 e 1.27 F 2.75 3.35 3.05 H 2.11 2.71 2.41 L 0.62 0.82 0.72 N 0.35 Q 0.60 0.70 0.65 All Dimensions in mm Suggested Pad Layout SO-8EP X Exposed Pad X1 C1 Y1 Dimensions X Y X1 Y1 C1 C2 Value (in mm) 0.60 1.55 3.30 2.66 5.4 1.27 Y C2 AP8802H Document number: DS32227 Rev. 7 - 2 13 of 14 www.diodes.com July 2015 © Diodes Incorporated AP8802H 60V 1A LED STEP-DOWN 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). 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