® RT8479 Two-Stage Hysteretic LED Driver with Internal MOSFETs General Description Features The RT8479 is a two-stage controller with dual MOSFETs and consists of a Boost converter (first stage) and a Buck converter (second stage). The advantage of two-stage topology is highly compatible with ET (Electronic Transformer) and extremely high Power Factor performance in MR16 / AR111 lighting market fields applications. Two-Stage Topology (Boost + Buck) Dual MOSFETs Inside Wide Input Voltage Range : 4.5V to 36V Excellent Power Factor Programmable Boost Output Voltage Independent Dual Stage Function Programmable LED current with ±5% LED Current Accuracy Input Under-Voltage Lockout Detection Thermal Shutdown Protection SOP-8 (Exposed Pad) Package RoHS Compliant and Halogen Free The first stage is a Boost converter for constant voltage output with inductor peak current over-current protection. The second stage is a Buck converter for constant output current by typical constant peak current regulation. The RT8479 is equipped with dual output gate drivers for internal power MOSFETs. The RT8479 is available in the SOP-8 (Exposed Pad) package. Ordering Information RT8479 Package Type SP : SOP-8 (Exposed Pad-Option 2) Lead Plating System G : Green (Halogen Free and Pb Free) Applications MR16 Lighting Signage and Decorative LED Lighting Architectural Lighting High Power LED Lighting Low Voltage Industrial Lighting Indicator and Emergency Lighting Automotive LED Lighting Note : Richtek products are : RoHS compliant and compatible with the current require- Suitable for use in SnPb or Pb-free soldering processes. ments of IPC/JEDEC J-STD-020. Simplified Application Circuit L1 D1 VCC R1 D2 VL AC 12V D5 ISN CIN C1 Copyright © 2014 Richtek Technology Corporation. All rights reserved. September 2014 LED- C2 VCOMP D4 D6 C3 CREG LX1 D3 RSENSE LED+ R2 VN DS8479-01 RT8479 OVP VCC COUT L2 LX2 GND is a registered trademark of Richtek Technology Corporation. www.richtek.com 1 RT8479 Marking Information Pin Configurations (TOP VIEW) RT8479GSP : Product Number RT8479 GSPYMDNN YMDNN : Date Code 8 LX1 OVP 2 GND 3 VCOMP 4 GND LX2 7 CREG 6 VCC 5 ISN 9 SOP-8 (Exposed Pad) Functional Pin Description Pin No. Pin Name Pin Function 1 LX1 Switch Node. The first stage internal MOSFET Drain. 2 OVP Over-Voltage Protection Sense Input. 3, 9 (Exposed Pad) GND Ground. The exposed pad must be soldered to a large PCB and connected to GND for maximum power dissipation. 4 VCOMP Compensation Node. A compensation network between VCOMP and GND is needed. 5 ISN LED Negative Current Sense Input. 6 VCC Supply Voltage Input. For good bypass, place a ceramic capacitor near the VCC pin. 7 CREG Internal Regulator Output. Place an 1F capacitor between the CREG and GND pins. 8 LX2 Switch Node. The second stage internal MOSFET Drain. Function Block Diagram ISN VCC -130mV Regulator V VCC + - UV/OV CREG LX2 OVP Core Logic EN2 EN2 EN1 LX1 EN1 VCOMP + - Copyright © 2014 Richtek Technology Corporation. All rights reserved. www.richtek.com 2 GND is a registered trademark of Richtek Technology Corporation. DS8479-01 September 2014 RT8479 Operation The RT8479 VCC is supplied from the first stage Boost output. The first stage is a constant output voltage Boost topology and senses the peak inductor current for over-current protection with excellent Power Factor. The second stage is a constant output current Buck topology. The current sense voltage threshold between the VCC and ISN pins is only 130mV to reduce power loss. Copyright © 2014 Richtek Technology Corporation. All rights reserved. DS8479-01 September 2014 is a registered trademark of Richtek Technology Corporation. www.richtek.com 3 RT8479 Absolute Maximum Ratings (Note 1) Supply Voltage, VCC to GND -----------------------------------------------------------------------------------------CREG, OVP, VCOMP to GND ----------------------------------------------------------------------------------------LX1, LX2 to GND ----------------------------------------------------------------------------------------------------------VCC to ISN ----------------------------------------------------------------------------------------------------------------Power Dissipation, PD @ TA = 25°C −0.3V to 45V −0.3V to 6V −0.3V to 40V −1V to 3V SOP-8 (Exposed Pad) --------------------------------------------------------------------------------------------------Package Thermal Resistance (Note 2) SOP-8 (Exposed Pad), θJA ---------------------------------------------------------------------------------------------SOP-8 (Exposed Pad), θJC --------------------------------------------------------------------------------------------Junction Temperature ----------------------------------------------------------------------------------------------------Lead Temperature (Soldering, 10 sec.) ------------------------------------------------------------------------------Storage Temperature Range -------------------------------------------------------------------------------------------ESD Susceptibility (Note 3) HBM (Human Body Model) ---------------------------------------------------------------------------------------------MM (Machine Model) ----------------------------------------------------------------------------------------------------- 3.44W Recommended Operating Conditions 29°C/W 2°C/W 150°C 260°C −65°C to 150°C 2kV 200V (Note 4) Supply Input Voltage, VCC ---------------------------------------------------------------------------------------------- 4.5V to 36V Junction Temperature Range -------------------------------------------------------------------------------------------- −40°C to 125°C Ambient Temperature Range -------------------------------------------------------------------------------------------- −40°C to 85°C Electrical Characteristics (VCC = 10VDC, No Load, CLOAD = 1nF, TA = 25°C, unless otherwise specified) Parameter Symbol Test Conditions Min Typ Max Unit Supply Voltage CREG UVLO_ ON VUVLO_ ON OVP = 0V -- 4.2 -- V CREG UVLO_ OFF VUVLO_ OFF OVP = 0V -- 3.9 -- V VCC Shutdown Current ISHDN VCC = 3.5V -- 10 -- A VCC Quiescent Current IQ VCC = 10V -- 1.5 -- mA Internal Reference Voltage VCREG -- 5 -- V -- 4.9 -- V -- 5 -- s Supply Current Internal Reference Voltage (ICREG = 20mA) I CREG = 20mA Stage 1 Max On-Time Stage 1 OVP High-Lev el VOVP_H 1.85 1.94 2.04 Low-Level VOVP_L 1.52 1.6 1.68 -- 1 -- OVP Pin Leakage Current IOVP Copyright © 2014 Richtek Technology Corporation. All rights reserved. www.richtek.com 4 V A is a registered trademark of Richtek Technology Corporation. DS8479-01 September 2014 RT8479 Parameter ISN Threshold Symbol Test Conditions Min Typ Max Unit 123.5 130 136.5 mV (dV1 + dV2) / 2 -- 15 -- % VISN Stage 2 Peak to Peak Sense Voltage LX1 Internal Switch RDS(ON) RDS(ON)_1 Sink = 100mA -- 0.2 -- LX2 Internal Switch RDS(ON) RDS(ON) _2 Sink = 100mA -- 0.3 -- 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 at TA = 25°C on a high effective thermal conductivity four-layer test board per JEDEC 51-7. θJC is measured at the exposed pad 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 © 2014 Richtek Technology Corporation. All rights reserved. DS8479-01 September 2014 is a registered trademark of Richtek Technology Corporation. www.richtek.com 5 RT8479 Typical Application Circuit L1 10µH D1 CIN 1µF VN D3 VCC R1 130k D2 VL AC 12V D5 D4 COUT 4.7µF RT8479 2 OVP VCC 6 R2 10k 1 LX1 4 VCOMP C1 0.47µF ISN 5 CREG 7 COUT_EC 220µF RSENSE 250m LED+ C5 C2 4.7µF C3 4.7µF 4LED D6 LED- L2 68µH LX2 8 GND 3, 9 (Exposed Pad) D1,D2, D3, D4, D5, D6 = PMEG4020 C5 depends on PCB layout and noise immunity. Copyright © 2014 Richtek Technology Corporation. All rights reserved. www.richtek.com 6 is a registered trademark of Richtek Technology Corporation. DS8479-01 September 2014 RT8479 Typical Operating Characteristics Quiescent Current vs. Temperature 3.5 1.6 3.0 Quiescent Current (mA) Quiescent Current (mA) Quiescent Current vs.VCC 1.7 1.5 1.4 1.3 1.2 2.5 2.0 1.5 1.0 0.5 OVP = 5V VCC = 4.5V to 30V, OVP = 5V 0.0 1.1 4 9.2 14.4 19.6 24.8 -50 30 -25 0 Operating Current vs. VCC 75 125 Operating Current vs. Temperature Operating Current (mA) 3.2 2.8 2.4 2.0 VCC = 4.5V to 30V, LX1/LX2 Capacitor = 1nF, OVP = 0V 3.5 3.0 2.5 2.0 1.5 VCC = 10V, LX1/LX2 Capacitor = 1nF, OVP = 0V 1.0 1.6 4 9.2 14.4 19.6 24.8 -50 30 -25 0 VCC (V) 25 50 75 100 125 Temperature (°C) CREG Voltage vs. VCC CREG Voltage vs. Temperature 7 5.4 5.3 CREG Voltage (V) 6 ICREG = 0mA 5 ICREG = −20mA 4 3 5.2 ICREG = 0mA 5.1 ICREG = −20mA 5.0 4.9 VCC = 4.5V to 30V 2 VCC = 10V 4.8 4.5 9.6 14.7 19.8 24.9 VCC (V) Copyright © 2014 Richtek Technology Corporation. All rights reserved. DS8479-01 100 4.0 3.6 Operating Current (mA) 50 Temperature (°C) VCC (V) CREG Voltage (V) 25 September 2014 30 -50 -25 0 25 50 75 100 125 Temperature (°C) is a registered trademark of Richtek Technology Corporation. www.richtek.com 7 RT8479 ISN Threshold vs. Temperature ISN Threshold vs. VCC 150 150 140 ISN Threshold (V) ISN Threshold (mV) 140 130 120 130 120 110 110 100 VCC = 10V VCC = 4.5V to 30V 90 100 4 9.2 14.4 19.6 24.8 -50 30 -25 0 OVP Hi/Low Level Voltage vs. VCC 75 100 125 OVP Hi/Low Level Voltage vs. Temperature 2.2 2.0 Hi 1.9 1.8 1.7 Low 1.6 1.5 VCC = 4.5V to 30V OVP Hi/Low Level Voltage (V) 2.1 OVP Hi/Low Level Voltage (V) 50 Temperature (°C) VCC (V) 1.4 2.1 2.0 Hi 1.9 1.8 1.7 Low 1.6 1.5 1.4 VCC = 10V 1.3 4.5 9.6 14.7 19.8 24.9 30 -50 -25 0 VCC (V) 25 50 75 100 125 Temperature (°C) LX1_RDS(ON) vs. Temperature LX2_RDS(ON) vs. Temperature 0.25 0.30 0.25 LX2 RDS(ON) (Ω) 0.20 LX1 RDS(ON) (Ω) 25 0.15 0.10 0.05 0.20 0.15 0.10 0.05 VCC = 10V 0.00 VCC = 10V 0.00 -50 -25 0 25 50 75 100 Temperature (°C) Copyright © 2014 Richtek Technology Corporation. All rights reserved. www.richtek.com 8 125 -50 -25 0 25 50 75 100 125 Temperature (°C) is a registered trademark of Richtek Technology Corporation. DS8479-01 September 2014 RT8479 LED Current vs. Output Voltage 440 440 435 LED Current (mA) LED Current (mA) LED Current vs. Input Voltage 450 430 420 410 400 430 425 420 415 390 Load = 1LED to 6LED VCC = 7V to 20V, IOUT = 420mA, Load = 4LED 410 380 6 8 10 12 14 16 18 4.5 20 7.6 10.7 Input Voltage (V) PK-Current vs. Temperature 16.9 20 CREG UVLO vs. Temperature 5.0 2500 4.5 2000 UVLO-H VC = 5V 4.0 UVLO (V) PK-Current (mA) 13.8 Output Voltage (V) 1500 1000 VC = 0V UVLO-L 3.5 3.0 500 2.5 VCC = 10V 0 2.0 -50 -25 0 25 50 75 100 125 -50 0 25 50 75 Temperature (°C) Power On from VCC Power Off from VCC IOUT (500mA/Div) IOUT (500mA/Div) LX2 (50V/Div) LX2 (50V/Div) VOUT (10V/Div) VOUT (10V/Div) V CC (10V/Div) V CC (10V/Div) VCC = 10V, 4LEDs Time (25ms/Div) Copyright © 2014 Richtek Technology Corporation. All rights reserved. DS8479-01 -25 Temperature (°C) September 2014 100 125 VCC = 10V, 4LEDs Time (25ms/Div) is a registered trademark of Richtek Technology Corporation. www.richtek.com 9 RT8479 Power On from AC-IN Power Off from AC-IN IOUT (200mA/Div) IOUT (200mA/Div) VOUT (10V/Div) VOUT (10V/Div) V CC (20V/Div) AC-IN (50V/Div) V CC (20V/Div) AC-IN (50V/Div) Time (10ms/Div) Copyright © 2014 Richtek Technology Corporation. All rights reserved. www.richtek.com 10 Time (10ms/Div) is a registered trademark of Richtek Technology Corporation. DS8479-01 September 2014 RT8479 Application Information Thermal Considerations The maximum power dissipation depends on the operating ambient temperature for fixed T J(MAX) and thermal resistance, θJA. The derating curve in Figure 1 allows the designer to see the effect of rising ambient temperature on the maximum power dissipation. 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 : Maximum Power Dissipation (W)1 3.6 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 SOP-8 (Exposed Pad) package, the thermal resistance, θJA, is 29°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 formula : Four-Layer PCB 3.0 2.4 1.8 1.2 0.6 0.0 0 25 50 75 100 125 Ambient Temperature (°C) Figure 1. Derating Curve of Maximum Power Dissipation P D(MAX) = (125°C − 25°C) / (29°C/W) = 3.44W for SOP-8 (Exposed Pad) package Layout Consideration Locate input capacitor as close to the VCC as possible. D6 L1 VCC R4 OVP R5 RSENSE COUT C15 D7 C6 GND D1 D2 CIN L2 LX1 VL VN D3 D4 OVP 2 GND 3 VCOMP 4 GND 8 LX2 7 CREG 6 VCC 5 ISN 9 ISN LED+ C8 C4 C5 LED- C3 C5: VCC-ISN bypass capacitor; noise interference like inductive and magnetic pick up will be rejected by C5. GND Figure 2. PCB Layout Guide Copyright © 2014 Richtek Technology Corporation. All rights reserved. DS8479-01 September 2014 is a registered trademark of Richtek Technology Corporation. www.richtek.com 11 RT8479 Outline Dimension H A M EXPOSED THERMAL PAD (Bottom of Package) Y J X B F C I D Dimensions In Millimeters Dimensions In Inches Symbol 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 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. www.richtek.com 12 DS8479-01 September 2014