RT9284B20GJ6

RT9284A/B Tiny Package, High Performance, Constant Current Switching Regulator for White LED General Description The RT9284A/B is a compact, high efficient and high integration LED driver. Internal 22V MOSFET can support 2 to 5 White LEDs for backlighting and camera flashing. Highly integration and internal compensation network minimizes as 5 external component counts. Optimized operation frequency can meet the requirement of small LC filters value and low operation current with high efficiency. Internal soft start function can reduce the inrush current. Tiny package type of TSOT-23-5 and TSOT-23-6 packages provide the best solution for PCB space saving and total BOM cost. Features VIN Operating Range : 2.7V to 5.5V Maximum Output Voltage up to 20V Dimming with Zero-inrush and Wide Frequency Range of 100 to 100kHz Over Voltage Protection Output Current up to 100mA at VOUT = 12V. Zero Shutdown Supply Current Minimize the External Component Small LC Filter Internal Soft Start RoHS Compliant and 100% Lead (Pb)-Free Ordering Information RT9284 () Package Type J5 : TSOT-23-5 J6 : TSOT-23-6 Operating Temperature Range P : Pb Free with Commercial Standard G : Green (Halogen Free with Commercial Standard) OVP Voltage 15 : 15V 20 : 20V FB Voltage A : 1.235V B : 0.25V Note : Richtek Pb-free and Green products are : RoHS compliant and compatible with the current requirements of IPC/JEDEC J-STD-020. Suitable for use in SnPb or Pb-free soldering processes. 100% matte tin (Sn) plating. Applications Camera Flash White LED Mobile Phone, Smart Phone LED Backlight PDA LED Backlight Digital Still Camera Camcorder Pin Configurations TOP VIEW VDD 5 1 LX 2 GND EN 4 3 FB TSOT-23-5 VDD OVP 6 1 LX 5 2 GND EN 4 3 FB Marking Information For marking information, contact our sales representative directly or through a Richtek distributor located in your area, otherwise visit our website for detail. TSOT-23-6 Note : There is no pin1 indicator on top mark for TSOT-23-6 type, and pin 1 will be lower left pin when reading top mark from left to right. DS9284A/B-05 August 2007 www.richtek.com 1 RT9284A/B Typical Application Circuit L1 4.7uH to 22uH VIN + 2.7V to 5.5V D1 SS0520 OVP 15V C2 1uF/16V ILED C1 1uF 6 RT9284 1 LX VDD EN GND OVP 5 Dimming Control 100Hz-100kHz 4 2 FB 3 R1 Figure 1. Application for Driving 3 Series WLEDs L1 4.7uH to 22uH VIN + 2.7V to 5.5V D1 SS0520 OVP 18V C2 1uF/25V ILED C1 1uF 6 RT9284 1 LX VDD EN GND OVP 5 OVP 15V R2 600k Dimming Control 100Hz-100kHz 4 2 FB 3 R1 Figure 2. Application for Driving 4 Series WLEDs L1 4.7uH to 22uH VIN + 2.7V to 5.5V D1 SS0520 OVP 20V C2 1uF/25V ILED C1 1uF 6 RT9284B 1 LX VDD EN GND OVP 5 Dimming Control 100Hz-100kHz 4 2 FB 3 VFB = 0.25V R1 Figure 3. Application for Driving 5 Series WLEDs L1 4.7uH to 22uH VIN + 2.7V to 5.5V D1 OVP SS0520 15V VOUT 12V R1 130k C2 1uF/16V C1 1uF 6 4 2 RT9284A 1 LX VDD EN GND OVP 5 FB 3 VFB = 1.235V R2 15k Figure 4. Application for Constant Output Voltage www.richtek.com 2 DS9284A/B-05 August 2007 RT9284A/B Pin Description Pin No. TSOT-23-5 TSOT-23-6 1 2 3 1 2 3 LX GND FB Switch Pin. Connect this Pin to inductor and catch diode. Minimize the track area to reduce EMI. Ground Pin Feedback Reference Voltage Pin. Series connect a resistor between WLED and ground as a current sense. Sense the current feedback voltage to set the current rating. Chip Enable (Active High). Voltage sensing input to trigger the function of over voltage protection. Note that this pin is high impedance. There should be a pull low 100kΩ resistor connected to GND when the control signal is floating. Over Voltage Protection Pin. Voltage sensing input to trigger the function of over voltage protection. Leave it unconnected to disable this function. Supply Input Voltage Pin. Bypass 1uF capacitor to GND to reduce the input noise. Pin Name Pin Function 4 4 EN -5 5 6 OVP VDD Function Block Diagram 1.2MHz OSC VDD Current Bias BandGap Protection Circuit OVP OVP UVLO Timer 5ms + Buffer + EN Soft Start VREF FB GND ibias VREF OCP 750mA PWM Logic LX DS9284A/B-05 August 2007 www.richtek.com 3 RT9284A/B Absolute Maximum Ratings (Note 1) −0.3V to 7V −0.3V to 22V −0.3V to 22V −0.3V to 6V 0.455W 0.455W 220°C/W 220°C/W 260°C 150°C −65°C to 150°C 2kV 200V Supply Input Voltage -----------------------------------------------------------------------------------------------------LX Input Voltage ----------------------------------------------------------------------------------------------------------OVP Voltage ---------------------------------------------------------------------------------------------------------------The Other Pins ------------------------------------------------------------------------------------------------------------Power Dissipation, PD @ TA = 25°C TSOT-23-5 ------------------------------------------------------------------------------------------------------------------TSOT-23-6 ------------------------------------------------------------------------------------------------------------------Package Thermal Resistance (Note 4) TSOT-23-5, θJA ------------------------------------------------------------------------------------------------------------TSOT-23-6, θJA ------------------------------------------------------------------------------------------------------------Lead Temperature (Soldering, 10 sec.) ------------------------------------------------------------------------------Junction Temperature ----------------------------------------------------------------------------------------------------Storage Temperature Range -------------------------------------------------------------------------------------------ESD Susceptibility (Note 2) HBM (Human Body Mode) ---------------------------------------------------------------------------------------------MM (Machine Mode) ------------------------------------------------------------------------------------------------------ Recommended Operating Conditions (Note 3) Supply Input Voltage ------------------------------------------------------------------------------------------------------ 2.7V to 5.5V Junction Temperature Range -------------------------------------------------------------------------------------------- −40°C to 125°C Ambient Temperature Range -------------------------------------------------------------------------------------------- −40°C to 85°C Electrical Characteristics (VIN = 3.7V, TA = 25°C unless otherwise specified) Parameter System Supply Input Operation voltage Range Under Voltage Lock Out Quiescent Current Supply Current Shut Down Current Line Regulation Oscillator Operation Frequency Maximum Duty Cycle Dimming Frequency Reference Voltage Symbol Test Condition Min Typ Max Units VDD VDD IDD IDD IDD FB = 1.5V, No switch FB = 0V, Switch VEN < 0.4V VIN : 3.0~4.3V 2.7 1.8 50 0.1 --- -2.2 300 2 -3 5.5 2.5 1000 3 1 -- V V uA mA uA % fOSC 0.9 85 100 1.2 --- 1.5 -100k MHz % Hz RT9284A Feedback Voltage (Note 5) RT9284B 1.173 0.237 1.235 0.25 1.296 0.263 V V To be continued www.richtek.com 4 DS9284A/B-05 August 2007 RT9284A/B Parameter MOSFET On Resistance of MOSFET Protection OVP Threshold OVP Sink Current OCP Shut Down Voltage Enable Voltage VEN VEN for 2,3,4 WLEDs application VOVP for 5 WLED application 14 19 ---1.5 15 20 5 750 --16 21 --0.4 -V V μA mA V V RDS(ON) -0.75 -Ω Symbol Test Condition Min Typ Max Units Note 1. Stresses listed as the above “ Absolute Maximum Ratings” may cause permanent damage to the device. These are for stress ratings. Functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may remain possibility to affect device reliability. Note 2. Devices are ESD sensitive. Handling precaution recommended. Note 3. The device is not guaranteed to function outside its operating conditions. Note 4. θJA i s measured in the natural convection at T A = 25 °C on a low effective thermal conductivity test board of JEDEC 51-3 thermal measurement standard. Note 5. Floating the OVP pin to disable OVP function. DS9284A/B-05 August 2007 www.richtek.com 5 RT9284A/B Typical Operating Characteristics Enable Voltage vs. Input Voltage 1.2 1.1 1.2 Shut Down Voltage vs. Input Voltage 1.1 -45°C Shut Down Voltage (V) Enable Voltage (V) -45°C 1 0.9 0.8 0.7 0.6 0.5 1.0 25°C 0.9 0.8 0.7 0.6 0.5 3 3.25 3.5 3.75 4 4.25 4.5 4.75 5 5.25 5.5 25°C 85°C 85°C 3 3.25 3.5 3.75 4 4.25 4.5 4.75 5 5.25 5.5 Input Voltage (V) Input Voltage (V) Efficiency vs. Input Voltage 84 83.5 83 LED Current vs. Input Voltage 22 21.5 ILED = 20mA, L = 4.7μH, DCR = 0.15Ω 4WLEDs, L = 10μH LED Current (mA) 3WLEDs 21 20.5 20 19.5 19 18.5 18 Efficiency (%) 82.5 4WLEDs 82 81.5 81 80.5 3 3.2 3.4 3.6 3.8 4 4.2 4.4 3 3.25 3.5 3.75 4 4.25 4.5 4.75 5 5.25 5.5 Input Voltage (V) Input Voltage (V) Maximum Duty Cycle vs. VDD 91% 91 2.7 2.5 2.3 POR (Rising/Falling) vs. Temperature Maximum Duty Cycle (%) 90% 90 89% 89 88% 88 Rising POR (V) 2.1 1.9 1.7 1.5 Falling 87 87% 86 86% 85 85% 3 3.25 3.5 3.75 4 4.25 4.5 4.75 5 5.25 5.5 -40 -30 -20 -10 0 10 20 30 40 50 60 70 80 90 VDD (V) www.richtek.com 6 Temperature (°C) DS9284A/B-05 August 2007 RT9284A/B Switching Current vs. Input Voltage 2 Switching Frequency vs. Temperature 1.5 Switching Current (mA) 1.6 1.4 1.2 1 0.8 0.6 0.4 0.2 0 3 3.25 3.5 3.75 4 4.25 4.5 4.75 25°C Switching Frequency (MHz) 1.8 -45°C 1.45 1.4 1.35 1.3 1.25 1.2 1.15 1.1 1.05 1 -40 -30 -20 -10 0 10 20 30 40 50 60 70 80 90 85°C 5 5.25 5.5 Input Voltage (V) Temperature (°C) Feedback Voltage vs. Temperature 252.2 252 Dimming Operation 4WLEDs, VIN = 3.7V, ILED = 20mA, L = 10μH (5V/Div) Feedback Voltage (mV) 251.8 251.6 251.4 251.2 251 250.8 250.6 -40 -30 -20 -10 0 10 20 30 40 50 60 70 80 90 EN I IN (50mA/Div) I LED (10mA/Div) f = 100Hz, Duty = 50% Temperature (°C) Time (2ms/Div) Dimming Operation 4WLEDs, VIN = 3.7V, ILED = 20mA, L = 10μH Dimming Operation 4WLEDs, VIN = 3.7V, ILED = 20mA, L = 10μH EN EN (5V/Div) (5V/Div) I IN (100mA/Div) I IN (100mA/Div) (10mA/Div) I LED (10mA/Div) I LED f = 1kHz, Duty = 50% f = 10kHz, Duty = 50% Time (400μs/Div) Time (40μs/Div) DS9284A/B-05 August 2007 www.richtek.com 7 RT9284A/B Dimming Operation 4WLEDs, VIN = 3.7V, ILED = 20mA, L = 10μH L = 10μH (10V/Div) (5V/Div) OCP EN VOUT I IN (100mA/Div) (10mA/Div) ILX (500mA/Div) I LED f = 100kHz, Duty = 50% LX (20V/Div) Time (4μs/Div) Time (25μs/Div) Inrush Current 4WLEDs, VIN = 3.0V, ILED = 20mA, L = 4.7μH (2V/Div) Inrush Current 4WLEDs, VIN = 4.3V, ILED = 20mA, L = 4.7μH (2V/Div) EN EN (2V/Div) (2V/Div) (5V/Div) VIN (5V/Div) VIN VOUT I IN (100mA/Div) VOUT I IN (100mA/Div) Time (500μs/Div) Time (500μs/Div) Normal Operation (5V/Div) (2V/Div) (2V/Div) 4WLEDs, VIN = 3.0V ILED = 20mA, L = 10μH (5V/Div) Normal Operation 4WLEDs, VIN = 3.7V ILED = 20mA, L = 10μH VOUT VIN LX (10V/Div) VOUT VIN LX (10V/Div) I IN (100mA/Div) I IN (100mA/Div) Time (400ns/Div) Time (400ns/Div) www.richtek.com 8 DS9284A/B-05 August 2007 RT9284A/B Normal Operation (5V/Div) (2V/Div) 4WLEDs, VIN = 4.3V ILED = 20mA, L = 10μH (5V/Div) (2V/Div) 4WLEDs, VIN = 5.5V ILED = 20mA, L = 10μH Normal Operation VOUT VIN LX (10V/Div) VOUT VIN LX (10V/Div) I IN (100mA/Div) I IN (100mA/Div) Time (400ns/Div) Time (400ns/Div) DS9284A/B-05 August 2007 www.richtek.com 9 RT9284A/B Application Information Power Sequence The RT9284A/B must take notice of the power sequence. The power sequence of RT9284A/B has to VDD early than EN or else the RT9284A/B maybe fall into the unknown state to result in RT9284A/B turn off. V DD > 2 .7V V DD EN > 1.5V EN EN < 0.4V b. Using a DC Voltage Using a variable DC voltage to adjust the brightness is a popular method in some applications. The dimming control using a DC voltage circuit is shown in Figure 6. According to the Superposition Theorem, as the DC voltage increases, the voltage contributed to VFB increases and the voltage drop on R2 decreases, i.e. the LED current decreases. For example, if the VDC range is from 0V to 2.8V, the selection of resistors in Figure 6 sets dimming control of LED current from 20mA to 0mA. V IN 2.7V to 5.5V C1 L1 4.7uH to 22uH D1 SS0520 V OUT Figure 5 LED Current Control The RT9284A/B regulates the LED current by setting the current sense resistor (R1) connecting to feedback and ground. As shown in Table 1, the RT9284A feedback voltage (VFB) is 1.235V and the RT9284B feedback voltage (VFB) is 0.25V. The LED current (ILED) can be set by a resistor R1. In order to have an accurate LED current, a precision resistor is preferred (1% is recommended). Table 1 Version RT9284A RT9284B Feedback Reference Voltage VFB (V) 1.235 0.25 LED Current Setting ILED (A) ILED = 1.235/R1 ILED = 0.25/R1 V EN > 1 .5V V EN < 0 .4V RT9284A 6 4 2 VDD EN GND LX OVP 1 5 C2 ILED FB 3 R3 13k V DC D imming 0V to 2.8V R2 10k R1 110 Figure 6. Dimming Control Using a DC Voltage for RT9284A The LED current can be calculated by the following equation. VFB − ILED = R2 × (VDC − VFB ) R3 R1 c. Using a Filtered PWM signal: Dimming Control a. Using a PWM Signal to EN Pin For controlling the LED brightness, the RT9284A/B can perform the dimming control by applying a PWM signal to EN pin. The internal soft start and the wide range dimming frequency from100 to100kHz can eliminate inrush current and audio noise when dimming. The average LED current is proportional to the PWM signal duty cycle. The magnitude of the PWM signal should be higher than the maximum enable voltage of EN pin, in order to let the dimming control perform correctly. www.richtek.com 10 Another common application is using a filtered PWM signal as an adjustable DC voltage for LED dimming control. A filtered PWM signal acts as the DC voltage to regulate the output current. The recommended application circuit is shown in the Figure 7. In this circuit, the output ripple depends on the frequency of PWM signal. For smaller output voltage ripple ( 1 .5V V EN < 0 .4V 4 2 EN GND OVP 5 R2 10k R3 10k R DC 3k 2.8V 0V PWM Signal C DC 1uF Input and output ceramic capacitors of 1 μ F are recommended for RT9284A/B applications. For better voltage filtering, ceramic capacitors with low ESR are recommended. X5R and X7R types are suitable because of their wider voltage and temperature ranges. Diode Selection Schottky diode is a good choice for RT9284A/B because of its low forward voltage drop and fast reverse recovery. Using Schottky diode can get better efficiency. The highspeed rectification is also a good characteristic of Schottky diode for high switching frequency. Current rating of the diode must meet the root mean square of the peak current and output average current multiplication as following : ID (RMS) ≈ (IOUT × IPEAK ) FB 3 R1 110 Figure 7. Filtered PWM Signal for LED Dimming Control of RT9284A The LED current can be calculated by the following equation. VFB − ILED = 20 18 16 R2 × (VPWM × Duty − VFB ) R3 + RDC R1 The diode’ s reverse breakdown voltage should be larger than the output voltage. SS0520 is recommended Schottky diode for rectifier. Layout Guide A full GND plane without gap break. VCC to GND noise bypass–Short and wide connection for the 1μF MLCC capacitor between Pin6 and Pin2. Minimized LX node copper area to reduce EMI. Minimized FB node copper area and keep far away from noise sources. LED Current (mA) 14 12 10 8 6 4 2 0 0 10 20 30 40 50 60 70 80 90 100 PWM Duty (%) Figure 8 Inductor Selection The recommended value of inductor for 3 to 5 WLEDs applications are 4.7 to 22μH. Small size and better efficiency are the major concerns for portable device, such as RT9284A/B used for mobile phone. The inductor should have low core loss at 1.2MHz and low DCR for better efficiency. To avoid inductor saturation current rating should be considered. Figure 9. Top Layer DS9284A/B-05 August 2007 www.richtek.com 11 RT9284A/B Figure 10. Bottom Layer www.richtek.com 12 DS9284A/B-05 August 2007 RT9284A/B Outline Dimension H D L C B b A A1 e Symbol A A1 B b C D e H L Dimensions In Millimeters Min 0.700 0.000 1.397 0.300 2.591 2.692 0.838 0.080 0.300 Max 1.000 0.100 1.803 0.559 3.000 3.099 1.041 0.254 0.610 Dimensions In Inches Min 0.028 0.000 0.055 0.012 0.102 0.106 0.033 0.003 0.012 Max 0.039 0.004 0.071 0.022 0.118 0.122 0.041 0.010 0.024 TSOT-23-5 Surface Mount Package DS9284A/B-05 August 2007 www.richtek.com 13 RT9284A/B H D L C B b A A1 e Symbol A A1 B b C D e H L Dimensions In Millimeters Min 0.700 0.000 1.397 0.300 2.591 2.692 0.838 0.080 0.300 Max 1.000 0.100 1.803 0.559 3.000 3.099 1.041 0.254 0.610 Dimensions In Inches Min 0.028 0.000 0.055 0.012 0.102 0.106 0.033 0.003 0.012 Max 0.039 0.004 0.071 0.022 0.118 0.122 0.041 0.010 0.024 TSOT-23-6 Surface Mount Package Richtek Technology Corporation Headquarter 5F, No. 20, Taiyuen Street, Chupei City Hsinchu, Taiwan, R.O.C. Tel: (8863)5526789 Fax: (8863)5526611 Richtek Technology Corporation Taipei Office (Marketing) 8F, No. 137, Lane 235, Paochiao Road, Hsintien City Taipei County, Taiwan, R.O.C. Tel: (8862)89191466 Fax: (8862)89191465 Email: marketing@richtek.com www.richtek.com 14 DS9284A/B-05 August 2007