® RT8471 1.2A/1A, Hysteretic, High Brightness LED Driver with Internal Switch General Description Features The RT8471 is a high efficiency, continuous mode inductive step-down converter, designed for driving single or multiple series connected LEDs from a voltage source higher than the LED voltage. It operates from an input voltage of 7V to 36V and employs hysteretic control with a high side current sense resistor to set the constant output current. The RT8471 includes an output switch and a high side output current sensing circuit, which uses an external resistor to set the nominal average output current. LED brightness control is achieved with PWM dimming from an analog or PWM input signal. The RT8471 is available in a small TSOT-23-5 package or a more thermal efficient SOP-8 (Exposed Pad) and MSOP8 (Exposed Pad) packages. Applications Ordering Information RT8471 Package Type J5 : TSOT-23-5 SP : SOP-8 (Exposed Pad-Option 1) FP : MSOP-8 (Exposed Pad) Lead Plating System G : Green (Halogen Free and Pb Free) (for MSOP-8 (Exposed Pad) and TSOT-23-5 ) Z : ECO (Ecological Element with Halogen Free and Pb free) (for SOP-8 (Exposed Pad) Only) Automotive LED Lighting High Power LED Lighting Indicator and Emergency Lighting Architectural Lighting Low Voltage Industrial Lighting Signage and Decorative LED Lighting Marking Information RT8471GJ5 01= : Product Code 01=DNN DNN : Date Code RT8471ZSP Note : Richtek products are : 7V to 36V Input Voltage Range Hysteretic Control with High Side Current Sensing Internal N-MOSFET with 350mΩ Ω Low RDS(ON) 1A Output Current (For TSOT-23-5 Only) 1.2A Output Current (For SOP-8 (Exposed Pad) and MSOP-8 (Exposed Pad) Only) Up to 97% Efficiency Typical ±5% LED Current Accuracy Analog or PWM Control Signal for LED Dimming 300Hz On-Board Ramp Generator Input Under Voltage Lockout Thermal Shutdown Protection RoHS Compliant and Halogen Free RoHS compliant and compatible with the current require- RT8471ZSP : Product Number RT8471 ZSPYMDNN YMDNN : Date Code ments of IPC/JEDEC J-STD-020. Suitable for use in SnPb or Pb-free soldering processes. RT8471GFP 0D= : Product Code 0D=YM DNN Copyright © 2013 Richtek Technology Corporation. All rights reserved. DS8471-02 December 2013 YMDNN : Date Code is a registered trademark of Richtek Technology Corporation. www.richtek.com 1 RT8471 Pin Configurations (TOP VIEW) VIN SENSE 5 4 2 VIN SENSE 2 GND 3 ADJ 4 3 GND 9 8 GND 7 LX 6 NC 5 NC SENSE GND GND ADJ VIN NC LX LX 8 2 3 GND 9 4 7 6 5 LX GND ADJ TSOT-23-5 MSOP-8 (Exposed Pad) SOP-8 (Exposed Pad) Typical Application Circuit VIN 7V to 36V CIN RS RT8471 VIN optional SENSE D ADJ GND L LX Functional Pin Description Pin No. TSO T-23-5 SOP-8 (Exposed Pad) MSOP-8 (Exposed Pad) 1 7 5, 6 2 Pin Name LX 3, 8, 2, 3, GND 9 (Exposed Pad) 9 (Exposed Pad) Pin Function Switch O utput Terminal. Dr ai n of inter nal N-MOSFET. Ground. The exposed pad must be soldered to a large PCB and connected to GND for maximum power dissipation. 3 4 4 ADJ 4 2 1 SENSE 5 1 8 VIN Dimming Control Input : --- Analog signal input for analog PWM dimming. --- PWM signal input for digital PWM dimming. Output Current Sense. Sense LED string current with an external resistor connected between VIN and SENSE. Supply Input Voltage. -- 5, 6 7 NC No Internal Connection. Copyright © 2013 Richtek Technology Corporation. All rights reserved. www.richtek.com 2 is a registered trademark of Richtek Technology Corporation. DS8471-02 December 2013 RT8471 Function Block Diagram VIN Regulator Bandgap SENSE + - UVLO UVLO VCC 1.25V + - UVLO Dimming Ramp Gen. LX GND + ADJ Dimming - Copyright © 2013 Richtek Technology Corporation. All rights reserved. DS8471-02 December 2013 is a registered trademark of Richtek Technology Corporation. www.richtek.com 3 RT8471 Absolute Maximum Ratings (Note 1) Supply Input Voltage, VIN ------------------------------------------------------------------------------------Switch Voltage, LX -------------------------------------------------------------------------------------------- Sense Voltage, SENSE ------------------------------------------------------------------------------------- All Other Pins ---------------------------------------------------------------------------------------------------- Power Dissipation, PD @ TA = 25°C TSOT-23-5 (Two-layer PCB) ---------------------------------------------------------------------------------TSOT-23-5 (Four-layer PCB) --------------------------------------------------------------------------------SOP-8 (Exposed pad, Two-layer PCB) -------------------------------------------------------------------SOP-8 (Exposed pad, Four-layer PCB) ------------------------------------------------------------------MSOP-8 (Exposed pad, Two-layer PCB) ----------------------------------------------------------------MSOP-8 (Exposed pad, Four-layer PCB) --------------------------------------------------------------- Package Thermal Resistance (Note 2) TSOT-23-5, θJA (Two-layer PCB) ---------------------------------------------------------------------------TSOT-23-5, θJC (Two-layer PCB) ---------------------------------------------------------------------------TSOT-23-5, θJA (Four-layer PCB) --------------------------------------------------------------------------TSOT-23-5, θJC (Four-layer PCB) --------------------------------------------------------------------------SOP-8 (Exposed pad, Two-layer PCB), θJA -------------------------------------------------------------SOP-8 (Exposed pad, Two-layer PCB), θJC -------------------------------------------------------------SOP-8 (Exposed pad, Four-layer PCB), θJA ------------------------------------------------------------SOP-8 (Exposed pad, Four-layer PCB), θJC ------------------------------------------------------------MSOP-8 (Exposed pad, Two-layer PCB), θJA ----------------------------------------------------------MSOP-8 (Exposed pad, Two-layer PCB), θJC ----------------------------------------------------------MSOP-8 (Exposed pad, Four-layer PCB), θJA ---------------------------------------------------------MSOP-8 (Exposed pad, Four-layer PCB), θJC --------------------------------------------------------- Junction Temperature ----------------------------------------------------------------------------------------- Lead Temperature (Soldering, 10 sec.) ------------------------------------------------------------------- Storage Temperature Range -------------------------------------------------------------------------------- ESD Susceptibility (Note 3) HBM (Human Body Model) ----------------------------------------------------------------------------------MM (Machine Model) ----------------------------------------------------------------------------------------- Recommended Operating Conditions −0.3V to 40V −0.3V to (VIN + 0.7V) (VIN − 5V) to (VIN + 0.3V) −0.3V to 6V 0.37W 0.43W 2.35W 3.26W 1.38W 2.1W 264.4°C/W 21.8°C/W 230.6°C/W 21.8°C/W 42.5°C/W 3.4°C/W 30.6°C/W 3.4°C/W 72°C/W 11.9°C/W 47.4°C/W 11.9°C/W 150°C 260°C −65°C to 150°C 2kV 200V (Note 4) Supply Input Voltage, VIN ------------------------------------------------------------------------------------- 7V to 36V Junction Temperature Range --------------------------------------------------------------------------------- −40°C to 125°C Copyright © 2013 Richtek Technology Corporation. All rights reserved. www.richtek.com 4 is a registered trademark of Richtek Technology Corporation. DS8471-02 December 2013 RT8471 Electrical Characteristics (VIN = 12V, TA = 25°C, unless otherwise specified) Parameter Symbol Mean Current Sense Threshold Voltage V SENSE Sense Threshold Hysteresis V SENSE Test Conditions Measure on SENSE Pin with Respecting to V IN. ADJ is Floating. Min Typ Max Unit 95 100 105 mV -- ±15 -- % Low Side Switch On-Resistance RDS(ON) Low Side Switch Leakage Current V LX = 12V, VADJ = 0V --- 350 0.01 500 10 m A Under Voltage Lockout Threshold V UVLO VIN Rising -- 5.2 -- V Under Voltage Lockout Threshold Hysteresis V UVLO -- 400 -- mV Ramp Frequency fRAMP -- 300 -- Hz Logic-High V ADJ, H 1.4 -- -- Logic-Low V ADJ, L -- -- 0.2 0.3 -- 1.3 Logic-High -- 1.2 1.3 Logic-Low 0.3 0.4 -- ADJ Input Threshold Voltage Analog Dimming Range Analog Dimming Threshold Voltage V V V Minimum Switch On-Time tON(MIN) LX Switch On -- 210 -- ns Minimum Switch Off-Time Quiescent Input Current with Output Off Quiescent Input Current with Output Switching Internal Propagation Delay tOFF(MIN) LX Switch Off -- 170 -- ns IVIN, Off V ADJ = 0V -- 450 -- A IVIN, On ADJ is Floating, fSW = 250kHz, V IN = 8V -- 1000 -- A tPD -- 25 -- ns Sense Pin Input Current ISENSE -- 300 -- nA Thermal Shutdown Thermal Shutdown Hysteresis TSD T SD --- 150 30 --- C C V SENSE = VIN 0.1V Note 1. Stresses beyond those listed “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and 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 may affect device reliability. Note 2. θJA is measured in natural convection at TA = 25°C on a two-layer and four-layer test board of JEDEC 51 thermal measurement standard. For SOP-8 (Exposed Pad) and MSOP-8 (Exposed Pad) the measurement case position of θJC is on the exposed pad of the package. For TSOT-23-5, the measurement case position of θJC is on the lead of the package. Note 3. Devices are ESD sensitive. Handling precaution is recommended. Note 4. The device is not guaranteed to function outside its operating conditions. Copyright © 2013 Richtek Technology Corporation. All rights reserved. DS8471-02 December 2013 is a registered trademark of Richtek Technology Corporation. www.richtek.com 5 RT8471 Typical Operating Characteristics Output Current vs. Input Voltage 1 LED 2 LED 3 LED 4 LED 5 LED 6 LED 7 LED 8 LED 9 LED 10 LED 1.03 Output Current (A) Output Current Deviation vs. Input Voltage 4%4 1.02 1.01 1.00 0.99 0.98 0.97 ILED = 1A, L = 33μH Output Current Deviation (%)1 1.04 1 LED 3%3 2 LED 3 LED 2%2 4 LED 5 LED 1%1 6 LED 7 LED 0%0 8 LED 9 LED 10 LED -1% -1 -2% -2 -3% -3 ILED = 1A, L = 33μH -4% -4 0.96 0 10 20 30 0 40 10 Input Voltage (V) Switching Frequency vs. Input Voltage 40 Duty Cycle vs. Input Voltage 100% 100 10 LED 9 LED 8 LED 7 LED 6 LED 5 LED 4 LED 3 LED 2 LED 1 LED 800 700 600 500 400 300 Duty Cycle (%) Duty Cycle (%) Switching Frequency (kHz)1 30 Input Voltage (V) 900 200 90% 90 10 LED 9 LED 80 8 LED 80% 7 LED 70 6 LED 70% 60 5 LED 60% 4 LED 50 3 LED 50% 2 LED 40 40% 1 LED 30 30% 20 20% 100 10 10% ILED = 1A, L = 33μH 0 0 10 20 30 ILED = 1A, L = 33μH 0%0 0 40 10 Input Voltage (V) Efficiency vs. Input Voltage 40 LX Switch On-Resistance vs. Temperature 560 (mΩ) On-Resistance (m ) 3 LED 90 90% 1 LED 85% 85 30 620 9LED 7 LED 95 95% 20 Input Voltage (V) 100 100% Efficiency (%) 20 80% 80 500 440 380 320 75% 75 ILED = 1A, L = 33μH 260 70% 70 0 10 20 30 Input Voltage (V) Copyright © 2013 Richtek Technology Corporation. All rights reserved. www.richtek.com 6 40 -50 -25 0 25 50 75 100 125 150 Temperature (°C) is a registered trademark of Richtek Technology Corporation. DS8471-02 December 2013 RT8471 Quiescent Input Current vs. Input Voltage Quiescent Input Current vs. Input Voltage 500 1000 800 600 400 200 VADJ = 2V 0 0 10 20 30 Quiescent Input Current (μA)1 Quiescent Input Current (μA) 1200 495 490 485 480 475 VADJ = 0V 470 40 0 10 Input Voltage (V) 1200 1000 1000 Output Current (mA) Output Current (mA) 40 Output Current vs. PWM Duty Cycle Output Current vs. PWM Duty Cycle 800 600 400 800 600 400 200 200 RS = 0.1Ω, fDimming = 10kHz 0 0% 20 20% 40 40% 60 60% 80 80% RS = 0.1Ω, fDimming = 500Hz 0 0 0% 100 100% 20 20% 40 40% 60 60% 80 80% 100 100% PWM Duty Cycle (%) PWM Duty Cycle (%) Output Current vs. ADJ Voltage Ramp Frequency vs. Temperature 1200 330 R = 100mΩ 325 800 Ramp Frequency (Hz)1 1000 Output Current (mA) 30 Input Voltage (V) 1200 0 20 R = 150mΩ 600 400 R = 350mΩ 200 320 315 310 305 300 295 VIN = 12V, 1LED 0 290 0.2 0.5 0.8 1.1 1.4 ADJ Voltage (V) Copyright © 2013 Richtek Technology Corporation. All rights reserved. DS8471-02 December 2013 1.7 -50 -25 0 25 50 75 100 125 150 Temperature (C) is a registered trademark of Richtek Technology Corporation. www.richtek.com 7 RT8471 Digital Dimming from ADJ On VADJ (2V/Div) Digital Dimming from ADJ Off VADJ (2V/Div) IOUT (500mA/Div) IOUT (500mA/Div) VIN = 12V, RS = 0.1Ω, fDimming = 500Hz, 1 LED VIN = 12V, RS = 0.1Ω, fDimming = 500Hz, 1 LED Time (5μs/Div) Time (5μs/Div) Power On from VIN Power Off from VIN VIN (5V/Div) VIN (5V/Div) IOUT (500mA/Div) IOUT (500mA/Div) RS = 0.1Ω, 1 LED Time (1ms/Div) Copyright © 2013 Richtek Technology Corporation. All rights reserved. www.richtek.com 8 RS = 0.1Ω, 1 LED Time (1ms/Div) is a registered trademark of Richtek Technology Corporation. DS8471-02 December 2013 RT8471 Application Information The RT8471 is a simple high efficiency, continuous mode inductive step-down converter. The device operates with an input voltage range from 7V to 36V and delivers up to 1.2A of output current. A high side current sense resistor sets the output current. A dedicated PWM dimming input enables pulsed LED dimming over a wide range of brightness levels. A high side current sensing scheme and an onboard current setting circuitry minimize the number of external components. A 1% sense resistor performs a ±5% LED current accuracy for the best performance. Under Voltage Lockout (UVLO) The RT8471 includes a UVLO feature with 400mV hysteresis. The internal MOSFET turns off when VIN falls below 4.8V (typ.). Setting Average Output Current The RT8471 output current which flows through the LEDs is set by an external resistor (RS) connected between the VIN and SENSE terminal. The relationship between output current (IOUT) and RS is shown as below : IOUTavg = 0.1V RS (A) Analog Dimming Control The ADJ terminal can be driven by an external voltage (VADJ) to adjust the average output current. The average output current is given by : V 0.4 IOUTavg = 0.1V ADJ 0.8 RS where VADJ is ranged from 0.4V to 1.2V. When VADJ is larger than 1.2V, the output current value will only depend on the external resistor (RS). Digital Dimming Control A Pulse Width Modulated (PWM) signal can drive the ADJ terminal directly. Notice that the PWM signal logic high level must be above 1.4V and the logic low level must be below 0.2V at the ADJ terminal. It's recommended to maintain the PWM dimming at low frequency (ex. 500Hz ) in order to obtain a linear dimming curve. PWM Soft-Start Behavior The RT8471 features an optional PWM soft-start behavior that allows for gradual brightness transition. This is achieved by simply connecting an external capacitor between the ADJ pin and GND. An internal current source will then charge this capacitor for soft-start behavior, resulting in steady LED current increase and decrease during power on and power off, as shown in Figure 1. 1.2V Internal VRAMP 0.4V VADJ 0V 1.2A ILED 0A Figure 1. PWM Soft-Start Behavior Mechanism Copyright © 2013 Richtek Technology Corporation. All rights reserved. DS8471-02 December 2013 is a registered trademark of Richtek Technology Corporation. www.richtek.com 9 RT8471 The capacitor can be selected according to below equation : t OFF C = 1.5 x 10-6 x tSS VOUT L IL VD VSEN IOUT RL tOFF(MIN) (170ns typ.) where tss is the soft-start period. where LED Current Ripple Reduction VD is the rectifier diode forward voltage (V) Higher LED current ripple will shorten the LED life time and increase heat accumulation of LED. There are two ways to reduce the LED current ripple. One way is by increasing the inductance to lower LED current ripple in absence of an output capacitor. The other way is by adding an output capacitor in parallel with the LED. This will then allow the use of a smaller inductor. VSEN is the voltage cross current sense resistor (V) Inductor Selection The inductance is determined by inductor current ripple, switching frequency, duty ratio, circuit specifications and component parameters, as expressed in the following equation : D L > VIN VOUT VSEN RDS(ON) IOUT f SW IL where fSW is the switching frequency (Hz) RDS(ON) is the low side switch on-resistance of internal MOSFET ( = 0.35Ω typical) RL is the inductor DC resistance (Ω) L is the inductance (H) The saturation current of the selected inductor must be higher than the peak output LED current, and the continuous current rating must be above the average output LED current. In general, the inductor saturation current should be 1.5 times the LED current. In order to reduce the output current ripple, a higher inductance is recommended at higher supply voltages. However, it could also cause a higher line resistance and result in a lower efficiency. Diode selection To obtain better efficiency, the Schottky diode is recommended for its low reverse leakage current, low recovery time and low forward voltage. With its low power dissipation, the Schottky diode outperforms other silicon diodes and increase overall efficiency. D is the duty cycle determined by VOUT/VIN IOUT is the required LED current (A) ΔIL is the inductor peak-peak ripple current (internally set to 0.3 x IOUT) VIN is the input supply voltage (V) VOUT is the total LED forward voltage (V) Besides, the selected inductance has also to satisfy the limit of the minimum switch on/off time. The calculated on time must be greater than 210ns of the minimum on time, and the off time must be greater than 170ns of the minimum off time. The following equation can be used to verify the suitability of the inductor value. tON L IL VIN VOUT IOUT RSEN RL RDS(ON) tON(MIN) (210ns typ.) Copyright © 2013 Richtek Technology Corporation. All rights reserved. www.richtek.com 10 Input Capacitor selection Input capacitor has to supply peak current to the inductor and flatten the current ripple on the input. The low ESR condition is required to avoid increasing power loss. The ceramic capacitor is recommended due to its excellent high frequency characteristic and low ESR, which are suitable for the RT8471. For maximum stability over the entire operating temperature range, capacitors with better dielectric are suggested. Thermal Protection A thermal protection feature is included to protect the RT8471 from excessive heat damage. When the junction temperature exceeds a threshold of 150°C, the thermal protection will turn off the LX terminal. When the junction temperature drops below 120°C, the RT8471 will turn back on the LX terminal and return to normal operations. is a registered trademark of Richtek Technology Corporation. DS8471-02 December 2013 RT8471 Thermal Considerations PD(MAX) = (TJ(MAX) − TA) / θJA where TJ(MAX) is the maximum junction temperature, TA is the ambient temperature, and θJA is the junction to ambient thermal resistance. For recommended operating condition specifications, the maximum junction temperature is 125°C. The junction to ambient thermal resistance, θJA, is layout dependent. For TSOT-23-5 packages, the thermal resistance, θJA, is 264.4°C/W on a standard JEDEC 51-3 two-layer thermal test board and 230.6°C/W on a standard JEDEC 51-7 fourlayer thermal test board. For SOP-8 (Exposed pad) package, the thermal resistance, θJA, is 42.5°C/W on a standard JEDEC 51-7 two-layer thermal test board, and 30.6°C/W on a standard JEDEC 51-7 four-layer thermal test board. For MSOP-8 (Exposed pad) package, the thermal resistance, θJA, is 72°C/W on a standard JEDEC 51-7 two-layer thermal test board, and 47.4°C/W on a standard JEDEC 51-7 four-layer thermal test board. The maximum power dissipation at TA = 25°C can be calculated by the following formulas : The maximum power dissipation depends on the operating ambient temperature for fixed T J(MAX) and thermal resistance, θJA. The derating curves in Figure 2 allow the designer to see the effect of rising ambient temperature on the maximum power dissipation. 4.0 Maximum Power Dissipation (W)1 For continuous operation, do not exceed absolute maximum junction temperature. The maximum power dissipation depends on the thermal resistance of the IC package, PCB layout, rate of surrounding airflow, and difference between junction and ambient temperature. The maximum power dissipation can be calculated by the following formula : SOP-8 (Exposed Pad, Four-Layer PCB) SOP-8 (Exposed Pad, Two-Layer PCB) MSOP-8 (Exposed Pad, Four-Layer PCB) MSOP-8 (Exposed Pad, Two-Layer PCB) TSOT23-5 (Four-Layer PCB) TSOT23-5 (Two-Layer PCB) 3.5 3.0 2.5 2.0 1.5 1.0 0.5 0.0 0 25 50 75 100 125 Ambient Temperature (°C) Figure 2. Derating Curves of Maximum Power Dissipation PD(MAX) = (125°C − 25°C) / (264.4°C/W) = 0.37W for TSOT-23-5 package (Two-Layer PCB) PD(MAX) = (125°C − 25°C) / (230.6°C/W) = 0.43W for TSOT-23-5 package (Four-Layer PCB) PD(MAX) = (125°C − 25°C) / (42.5°C/W) = 2.35W for SOP-8 (Exposed pad, Two-Layer PCB) package PD(MAX) = (125°C − 25°C) / (30.6°C/W) = 3.26W for SOP-8 (Exposed pad, Four-Layer PCB) package P D(MAX) = (125°C − 25°C) / (72°C/W) = 1.38W for MSOP-8 (Exposed pad, Two-Layer PCB) package PD(MAX) = (125°C − 25°C) / (47.4°C/W) = 2.1W for MSOP-8 (Exposed pad, Four-Layer PCB) package Copyright © 2013 Richtek Technology Corporation. All rights reserved. DS8471-02 December 2013 is a registered trademark of Richtek Technology Corporation. www.richtek.com 11 RT8471 Layout Considerations For best performance of the RT8471, please abide the following layout guide. The capacitor CIN, CADJ and external resistor, RS, must be placed as close as possible to the VIN and SENSE pins of the device respectively. The GND should be connected to a strong ground plane. Keep the main current traces as short and wide as possible. The inductor (L) should be mounted as close to the device with low resistance connections. The ADJ pin trace need to be kept far away from LX terminal. Place the resistor RS as close as possible to VIN and SENSE pins. RS VIN CIN GND D Place the capacitor CIN as close as possible to VIN pin. LED+ VIN SENSE 5 4 1 2 Place the capacitor CADJ as close as possible to the ADJ pin. 3 LX GND ADJ L CADJ LED- Figure 3. PCB Layout Guide Copyright © 2013 Richtek Technology Corporation. All rights reserved. www.richtek.com 12 is a registered trademark of Richtek Technology Corporation. DS8471-02 December 2013 RT8471 Outline Dimension H D L B C b A A1 e Symbol Dimensions In Millimeters Dimensions In Inches Min Max Min Max A 0.700 1.000 0.028 0.039 A1 0.000 0.100 0.000 0.004 B 1.397 1.803 0.055 0.071 b 0.300 0.559 0.012 0.022 C 2.591 3.000 0.102 0.118 D 2.692 3.099 0.106 0.122 e 0.838 1.041 0.033 0.041 H 0.080 0.254 0.003 0.010 L 0.300 0.610 0.012 0.024 TSOT-23-5 Surface Mount Package Copyright © 2013 Richtek Technology Corporation. All rights reserved. DS8471-02 December 2013 is a registered trademark of Richtek Technology Corporation. www.richtek.com 13 RT8471 H A M EXPOSED THERMAL PAD (Bottom of Package) Y J X B F C I D Dimensions In Millimeters Symbol Dimensions In Inches Min Max Min Max A 4.801 5.004 0.189 0.197 B 3.810 4.000 0.150 0.157 C 1.346 1.753 0.053 0.069 D 0.330 0.510 0.013 0.020 F 1.194 1.346 0.047 0.053 H 0.170 0.254 0.007 0.010 I 0.000 0.152 0.000 0.006 J 5.791 6.200 0.228 0.244 M 0.406 1.270 0.016 0.050 X 2.000 2.300 0.079 0.091 Y 2.000 2.300 0.079 0.091 X 2.100 2.500 0.083 0.098 Y 3.000 3.500 0.118 0.138 Option 1 Option 2 8-Lead SOP (Exposed Pad) Plastic Package Copyright © 2013 Richtek Technology Corporation. All rights reserved. www.richtek.com 14 is a registered trademark of Richtek Technology Corporation. DS8471-02 December 2013 RT8471 D L EXPOSED THERMAL PAD (Bottom of Package) U E V E1 e A2 A A1 b Symbol Dimensions In Millimeters Dimensions In Inches Min Max Min Max A 0.810 1.100 0.032 0.043 A1 0.000 0.150 0.000 0.006 A2 0.750 0.950 0.030 0.037 b 0.220 0.380 0.009 0.015 D 2.900 3.100 0.114 0.122 e 0.650 0.026 E 4.800 5.000 0.189 0.197 E1 2.900 3.100 0.114 0.122 L 0.400 0.800 0.016 0.031 U 1.300 1.700 0.051 0.067 V 1.500 1.900 0.059 0.075 8-Lead MSOP (Exposed Pad) Plastic Package Richtek Technology Corporation 14F, No. 8, Tai Yuen 1st Street, Chupei City Hsinchu, Taiwan, R.O.C. Tel: (8863)5526789 Richtek products are sold by description only. Richtek reserves the right to change the circuitry and/or specifications without notice at any time. Customers should obtain the latest relevant information and data sheets before placing orders and should verify that such information is current and complete. Richtek cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Richtek product. Information furnished by Richtek is believed to be accurate and reliable. However, no responsibility is assumed by Richtek or its subsidiaries for its use; nor for any infringements of patents or other rights of third parties which may result from its use. No license is granted by implication or otherwise under any patent or patent rights of Richtek or its subsidiaries. DS8471-02 December 2013 www.richtek.com 15