RT8415GSP

RT8415 Two-Stage Hysteretic LED Driver General Description Features The RT8415 is a two-stage LED driver controller with the 2nd stage MOSFET integrated inside. It consists of a Boost controller on the first stage and a Buck converter on the second stage. By adapting two-stage topology, RT8415 is highly compatible with ET (Electronic Transformer) and performs extremely high Power Factor in specific MR16 / AR111 LED lighting z Two-Stage Topology (Boost + Buck) 2nd Stage MOSFETs Inside Wide Input Voltage Range : 4.5V to 36V z z Excellent Power Factor Programmable Boost Output Voltage z z Independent Dual Stage Function Programmable LED Current with r6% LED Current Accuracy Flicker-Free LED Wide Electronic Transformer Compatibility Input Under Voltage Lockout Detection z z applications. z The Boost converter on the first stage provides constant output voltage with well inductor current control. The Buck converter on the second stage provides constant LED output current by hysteretic peak current regulation. z z z The RT8415 is available in the SOP-8 (Exposed Pad) Applications package. Ordering Information z MR16 Lighting z Signage and Decorative LED Lighting Architectural Lighting High Power LED Lighting Low Voltage Industrial Lighting z RT8415 Package Type SP : SOP-8 (Exposed Pad-Option 2) z Lead Plating System G : Green (Halogen Free and Pb Free) z z Indicator and Emergency Lighting Automotive LED Lighting z Note : Pin Configuration Richtek products are : f Thermal Shutdown Protection SOP-8 (Exposed Pad) Package z (TOP VIEW) RoHS compliant and compatible with the current requirements of IPC/JEDEC J-STD-020. f 8 GATE1 CS 2 OVP 3 VCOMP 4 Suitable for use in SnPb or Pb-free soldering processes. GND LX2 7 CREG 6 VCC 5 ISN 9 SOP-8 (Exposed Pad) Simplified Application Circuit D5 L1 D1 VCC R1 OVP D2 VL AC 12V ISN Q1 D3 GATE1 CS OVP D4 CS R4 July 2016 CREG VCOMP C1 Copyright © 2016 Richtek Technology Corporation. All rights reserved COUT C2 R2 VN DS8415-00 RT8415 VCC R3 BLD RSENSE ISN LED+ D6 C5 LED- C3 L2 LX2 GND is a registered trademark of Richtek Technology Corporation. www.richtek.com 1 RT8415 Marking Information RT8415 GSPYMDNN RT8415GSP : Product Number YMDNN : Date Code Functional Pin Description Pin No. Pin Name Pin Function 1 GATE1 The 1st stage output gate. 2 CS The 1st stage current sense input. 3 OVP Over-voltage protection sense input. 4 VCOMP Compensation node. A compensation network between VCOMP and GND is needed. 5 ISN LED current sense amplifier negative input. 6 VCC Power supply. For good bypass, place a ceramic capacitor near the VCC pin. 7 CREG Internal regulator output. Place a 4.7PF Capacitor between CREG and GND pins. 8 LX2 Switch node. The 2nd Stage Internal MOSFET Drain. 9 (Exposed Pad) GND Ground. The Exposed Pad must be soldered to a large PCB and connected to GND for maximum power dissipation. Copyright © 2016 Richtek Technology Corporation. All rights reserved www.richtek.com 2 is a registered trademark of Richtek Technology Corporation. DS8415-00 July 2016 RT8415 Functional Block Diagram ISN VCC -110mV V Regulator VCC CREG UV/OV LX2 EN2 OVP VCOMP Core Logic EN2 EN1 Duty Control CREG EN1 GATE1 GND CS Operation The RT8415 VCC is supplied from the first stage Boost output. The first stage is a constant output voltage Boost topology that controls the inductor current 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 110mV to minimize the power loss. Copyright © 2016 Richtek Technology Corporation. All rights reserved DS8415-00 July 2016 is a registered trademark of Richtek Technology Corporation. www.richtek.com 3 RT8415 Absolute Maximum Ratings (Note 1) y Supply Voltage, VCC to GND -------------------------------------------------------------------------------------- 0.3V to 40V z CREG, OVP, VCOMP, CS to GND -------------------------------------------------------------------------------- 0.3V to 6V z LX2 to GND ------------------------------------------------------------------------------------------------------------- 0.3V to 40V z VCC to ISN-------------------------------------------------------------------------------------------------------------- 0.3V to 3V z Power Dissipation, PD @ TA = 25°C z SOP-8 (Exposed Pad) ---------------------------------------------------------------------------------------------- 2.46W Package Thermal Resistance (Note 2) SOP-8 (Exposed Pad), TJA ---------------------------------------------------------------------------------------- 40.6°C/W SOP-8 (Exposed Pad), TJC ---------------------------------------------------------------------------------------- 2°C/W z Lead Temperature (Soldering, 10 sec.) ------------------------------------------------------------------------- 260qC z Junction Temperature ----------------------------------------------------------------------------------------------- 150qC z Storage Temperature Range -------------------------------------------------------------------------------------- 65qC to 150qC z ESD Susceptibility (Note 3) HBM (Human Body Model) ---------------------------------------------------------------------------------------- 2kV MM (Machine Model) ----------------------------------------------------------------------------------------------- 200V Recommended Operating Conditions (Note 4) z Supply Input Voltage, VCC ----------------------------------------------------------------------------------------- 4.5V to 36V z Ambient Temperature Range--------------------------------------------------------------------------------------- 40qC to 85qC z Junction Temperature Range -------------------------------------------------------------------------------------- 40qC to 125qC Electrical Characteristics (VCC = 20VDC, 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 = 2V -- 10 -- PA VCC Quiescent Current IQ -- 2 -- mA VCC OVP Trigger Level VCC_OVP -- 39 -- V Internal Reference Voltage VCREG -- 5 -- V -- 4.9 -- V Supply Current Internal Reference Voltage (ICREG = 20mA) ICREG = 20mA Boost Converter Stage 1 OVP High Level VOVP_H -- 1.88 -- V Low Level VOVP_L 1.52 1.6 1.68 V -- 1 -- PA -- 50 -- k: OVP Pin Leakage Current CS Input Impendence IOVP CS = 0.2V Copyright © 2016 Richtek Technology Corporation. All rights reserved www.richtek.com 4 is a registered trademark of Richtek Technology Corporation. DS8415-00 July 2016 RT8415 Parameter Symbol Test Conditions Min Typ Max Unit UGATE1 Drive Sink RUGATE1sk Sink = 50mA -- 2 -- : LGATE1 Drive Source RLGATE1sr Source = 50mA -- 1.5 -- : GATE1 Default Pull Down Resistor RLGATE1sr -- 90 -- k: 103 110 117 mV (dV1 + dV2) / 2 -- 15 -- % Sink = 100mA -- 0.2 -- : Over-Temperature Threshold TSD (Note 5) -- 150 -- o Over-Temperature Threshold 'TSD Hysteresis (Note 5) -- 30 -- o Buck Converter ISN Threshold VCCVISN Stage 2 Peak to Peak Sense Voltage LX2 Internal Switch RDS(ON) RDS(ON)_LX2 Temperature Protection C C 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. TJA is measured under natural convection (still air) at TA = 25qC with the component mounted on a low effective-thermal-conductivity two-layer test board on a JEDEC thermal measurement standard. TJC is measured at the exposed pad of the package. Note 3. Devices are ESD sensitive. Handling precaution recommended. Note 4. The device is not guaranteed to function outside its operating conditions. Note 5. Guaranteed by design. Copyright © 2016 Richtek Technology Corporation. All rights reserved DS8415-00 July 2016 is a registered trademark of Richtek Technology Corporation. www.richtek.com 5 RT8415 Typical Application Circuit L1 D1 D5 R1 OVP D2 LIN RIN VL AC 12V VCC C6 RT8415 6 VCC C2 R2 ISN VN CIN D3 Q1 D4 CS R4 C1 COUT 5 7 1 GATE1 CREG 2 CS 3 OVP 8 LX2 4 VCOMP R3 BLD RSENSE ISN LED+ D6 C5 LED- C3 L2 GND 9 (Exposed Pad) Copyright © 2016 Richtek Technology Corporation. All rights reserved www.richtek.com 6 is a registered trademark of Richtek Technology Corporation. DS8415-00 July 2016 RT8415 Typical Operating Characteristics Quiescent Current vs. Temperature 2.6 2.4 2.4 Quiescent Current (mA) Quiescent Current (mA) Quiescent Current vs. VCC 2.6 2.2 2.0 1.8 1.6 1.4 2.2 2.0 1.8 1.6 1.4 OVP = 5V, VCC = 30V OVP = 5V 1.2 1.2 0 5 10 15 20 25 30 35 -50 -25 0 25 50 75 100 125 Temperature (°C) VCC (V)   VCC OVP vs. Temperature CREG Voltage vs. VCC 42 7 6 CREG Voltage (V) VCC OVP (V) 40 38 36 34 5 ICREG = 0mA ICREG = 20mA 4 3 32 2 30 -50 -25 0 25 50 75 100 0 125 5 10 Temperature (°C) 15 20 25 30 35 VCC (V)   CREG Voltage vs. Temperature ISN Sense Threshold vs. VCC 130 ISN Sense Threshold (mV) 5.4 CREG Voltage (V) 5.3 5.2 5.1 ICREG = 0mA 5.0 ICREG = 20mA 4.9 125 120 115 110 105 100 95 90 85 VCC = 30V 80 4.8 -50 -25 0 25 50 75 100 0 125 5 10 15 20 25 30   Copyright © 2016 Richtek Technology Corporation. All rights reserved DS8415-00 July 2016 35 VCC (V) Temperature (°C) is a registered trademark of Richtek Technology Corporation. www.richtek.com 7 RT8415 LX2 RDS(ON) vs. VCC 0.30 130 0.25 LX2 RDS(ON) (Ω) ISN Sense Threshold (mV) ISN Sense Threshold vs. Temperature 140 120 110 100 90 0.20 0.15 0.10 0.05 VCC = 20V 80 0.00 -50 -25 0 25 50 75 100 125 Temperature (°C) 0 5 10 15 20 25 30 35 VCC (V)    LX2 RDS(ON) vs. Temperature 0.30 LX2 RDS(ON) (Ω) 0.25 0.20 0.15 0.10 0.05 VCC = 20V 0.00 -50 -25 0 25 50 75 100 125 Temperature (°C)   Copyright © 2016 Richtek Technology Corporation. All rights reserved www.richtek.com 8  is a registered trademark of Richtek Technology Corporation. DS8415-00 July 2016 RT8415 Application Information The RT8415 consists of a constant voltage Boost controller and a constant output current Buck controller. The Boost controller is based on a peak current, well PFC control architecture, and designed to operate up VCC Voltage Setting to 1MHz to use a very small inductor for space constrained applications. 1.88V, the power switch is turned off. The power switch can be turned on again once the voltage at the OVP pin Under-Voltage Lockout (UVLO) drops below 1.6V. For Boost applications, the output voltage can be set by the following equation : The RT8415 includes an under-voltage lockout function with 300mV hysteresis. The internal MOSFET turns off when VCC falls below 3.9V (typ.). VCC(MAX) = 1.88V u §¨1 + R1 ·¸ R2 ¹ © CREG Regulator R1 and R2 are the voltage divider resistors from VOUT to GND with the divider center node connected to the The CREG pin requires a capacitor for stable operation and to store the charge for the large GATE switching currents. Choose a 10V rated low ESR, X7R or X5R, ceramic capacitor for best performance. A 4.7PF capacitor will be adequate for many applications. Place the capacitor close to the IC to minimize the trace length to the CREG pin and to the IC ground. An internal current limit on the CREG output protects the RT8415 from excessive on-chip power dissipation. The CREG pin has set the output to 4.2V (typ.) to protect the internal FETs from excessive power dissipation caused by not being fully enhanced. If the CREG pin is used to drive extra circuits beside RT8415, the extra loads should be limited to less than 10mA. Average Output Current Setting The output current that flows through the LED string is set by an external resistor, RSENSE, which is connected between the VCC and ISN terminal. The relationship between output current, IOUT, and RSENSE is shown below : IOUT = 110mV RSENSE LED Current Ripple Reduction Higher LED current ripple will shorten the LED life time and increase heat accumulation of LED. To reduce the LED current ripple, an output capacitor in parallel with the LED should be added. The typical value of output capacitor is 4.7PF. The VCC voltage setting is equipped with an over-voltage protection (OVP) function. When the voltage at the OVP pin exceeds threshold approximately OVP pin. For MR16 LED lamp application, the minimum voltage of VCC should maintain above 25V for stable operation. The VCC voltage setting is equipped with an Over-Voltage Protection function. When the voltage at the VCC pin exceeds threshold approximately 39V, the power switch is turned off. Step-Down Converter Inductor Selection The RT8415 implemented a simple high efficiency, continuous mode inductive step-down converter. The inductance L2 in Buck converter is determined by the following factors : inductor ripple current, switching frequency, VOUT/VCC ratio, internal MOSFET, topology specifications, and component parameter. The inductance L2 is calculated according to the following equation : L2 t ª¬ VCC(MAX)  VOUT  0.11 RDS(ON)_LX2 u IOUT  º¼ u D2 f  SW2 u 'IOUT  where f SW2 is the switching frequency of Buck controller (Hz). RDS2(ON)_LX2 is the low-side switch on-resistance of internal MOSFET M2. The typical value is 0.2:. D2 is the duty cycle = VOUT / VCC. IOUT is the required LED current (A). 'IOUT is the inductor peak-peak ripple current (internally set to 0.3 x IOUT). VCC is the Buck input voltage (V). Copyright © 2016 Richtek Technology Corporation. All rights reserved DS8415-00 July 2016 is a registered trademark of Richtek Technology Corporation. www.richtek.com 9 RT8415 VOUT is the total LED forward voltage (V). L2 is the inductance (H). The selected inductor must have saturation current higher than the peak output LED current and continuous current rating above the required average output LED current. In general, the inductor saturation current should be 1.5 times the LED current. In order to minimize output current ripple, higher values of inductance are recommended at higher supply voltages. Because high values of inductance has high line resistance, it will cause lower efficiency. Step-Up Converter Inductor Selection The RT8415 uses a continuous mode and well inductor control to provide wide electronic transformer compatibility step-up converter. higher than the limit current of inductance L1. In general, the inductor saturation current should be 1.2 times the limit current of inductance L1. A 10PH to 22PH inductor will meet the demand of most of the RT8415 applications. 1st Stage Current Sense Resistor Selection The resistor, R4, between CS and GND should be selected to provide adequate switch current to drive the application without exceeding the current limit threshold set by the CS pin sense threshold of the RT8415. The Sense resistor value can be calculated according to the following equation : R4 = VCL IL1_LIMIT Where Following the continuous mode mechanism, the inductance L1 is calculated according to the following equation : IL1_LIMIT is the limit current of first inductor. L1 t ª¬ VIN  VFBR  RDS(ON)_Q1 u IL1   R4 u IL1  º¼ Diode Selection u D1  fSW1 u 'IL1  The limit current of first inductor is calculated according to the following equation : VCL is the current limit threshold (0.125V, typ.). 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 increases overall efficiency. V I L1_LIMIT = CL R4 where f SW1 is the switching frequency of Boost controller (Hz). RDS(ON)_Q1 is the switch on-resistance of external MOSFET Q1. D1 is the duty cycle = (VCC  VIN ) / VCC. IL1 is the input current. The typical value is 2A for MR16 application. 'IL1 is the inductor peak-peak ripple current (typically set to 0.055 / R4). VFBR is the bridge rectifier forward voltage (V). VIN is the supply input voltage (V). VCC is the Boost output voltage (V). VCL is the current limit threshold (0.125V, typ.). L1 is the inductance (H). R4 is the CS resistance (:). The selected inductor must have saturation current Copyright © 2016 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 is suitable for the RT8415. For maximum stability over the entire operating temperature range, capacitors with better dielectric are suggested. Thermal Protection A thermal protection feature is to protect the RT8415 from excessive heat damage. When the junction temperature exceeds 150qC, the thermal protection will turn off the GATE1 and LX2 terminals. When the junction temperature drops below 125qC, the RT8415 will turn on the GATE1 and LX2 terminals terminal and return to normal operation. is a registered trademark of Richtek Technology Corporation. DS8415-00 July 2016 RT8415 Thermal Considerations Maximum Power Dissipation (W)1 3.0 The junction temperature should never exceed the absolute maximum junction temperature TJ(MAX), listed under Absolute Maximum Ratings, to avoid permanent damage to the device. The maximum allowable power dissipation depends on the thermal resistance of the IC package, the PCB layout, the rate of surrounding airflow, and the difference between the junction and ambient temperatures. The maximum power dissipation can be calculated using the following formula : Two-Layer PCB 2.5 2.0 1.5 1.0 0.5 0.0 PD(MAX) = (TJ(MAX) TA) / TJA 0 where TJ(MAX) is the maximum junction temperature, TA is the ambient temperature, and TJA is the 25 50 75 100 125 Ambient Temperature (°C) Figure 1. Derating Curve of Maximum Power junction-to-ambient thermal resistance. Dissipation For continuous operation, the maximum operating junction temperature indicated under Recommended Operating Conditions is 125qC. The junction-to-ambient thermal resistance,TJA, is highly package dependent. For a SOP-8 (Exposed Pad) package, the thermal resistance, TJA, is 40.6qC/W on a standard JEDEC low effective-thermal-conductivity two-layer test board. The maximum power dissipation at TA = 25qC can be calculated as below : Layout Consideration PCB layout is very important to design power switching converter circuits. Some recommended layout guidelines are suggested as follows : f The power components L1, D5, Q1, CIN, and COUT must be placed as close to each other as possible to reduce the ac current loop area. The power PD(MAX) = (125qC 25qC) / (40.6qC/W) = 2.46W for a SOP-8 (Exposed Pad) package. components L2, D6, and LX2 pin of device must be The maximum power dissipation depends on the operating ambient temperature for the fixed TJ(MAX) and the ac current loop area. The PCB trace between the thermal resistance, TJA. The derating curves in Figure 1 allows the designer to see the effect of rising power components must be as short and wide as possible due to large current flow through these ambient temperature dissipation. traces during operation. on the maximum placed as close to each other as possible to reduce power f The capacitor COUT, C5 and external resistor, RSENSE, must be placed as close as possible to the VCC and ISN pins of the device respectively. f The GND should be connected to a strong ground plane. f Keep the main current traces as short and wide as possible. Copyright © 2016 Richtek Technology Corporation. All rights reserved DS8415-00 July 2016 is a registered trademark of Richtek Technology Corporation. www.richtek.com 11 RT8415 D5 L1 VIN VCC R1 COUT OVP R2 RSENSE C6 ISN LED+ D6 GND VL LIN D1 D2 RIN Q1 GATE1 CS 2 OVP 3 VCOMP 4 VN D3 D4 CIN R4 C5 L2 C1 GND 8 LX2 7 CREG 6 VCC 5 ISN 9 LED- C2 C3 GND CS Figure 2. PCB Layout Guide Copyright © 2016 Richtek Technology Corporation. All rights reserved www.richtek.com 12 is a registered trademark of Richtek Technology Corporation. DS8415-00 July 2016 RT8415 Outline Dimension 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 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. Copyright © 2016 Richtek Technology Corporation. All rights reserved DS8415-00 July 2016 is a registered trademark of Richtek Technology Corporation. www.richtek.com 13