RT8479BGSP Richtek

RT8479B Two-Stage Hysteretic LED Driver with Internal MOSFETs General Description Features zz z zz Two-Stage Topology (Boost + Buck) The RT8479B is a two-stage controller with dual zz z zz Dual MOSFETs Inside MOSFETs and consists of a Boost converter (first stage) zz z zz Wide Input Voltage Range : 4.5V to 36V and a Buck converter (second stage). The advantage of zz z zz Excellent Power Factor two-stage topology is highly compatible with ET (Electronic zz z zz Programmable Boost Output Voltage Transformer) and extremely high Power Factor zz z zz Independent Dual Stage Function performance in MR16 / AR111 lighting market fields zz z zz Programmable LED current with 5% LED Current applications. Accuracy The first stage is a Boost converter for constant voltage zz z zz Input Under-Voltage Lockout Detection output with inductor peak current over-current protection. zz z zz Thermal Shutdown Protection The second stage is a Buck converter for constant output current by typical constant peak current regulation. Ordering Information The RT8479B is equipped with dual output gate drivers RT8479B for internal power MOSFETs. Package Type SP : SOP-8 (Exposed Pad-Option 2) The RT8479B is available in the SOP-8 (Exposed Pad) package. Lead Plating System G : Green (Halogen Free and Pb Free) Note : Applications Richtek products are : z MR16 Lighting RoHS compliant and compatible with the current require- z Signage and Decorative LED Lighting ments of IPC/JEDEC J-STD-020. z Architectural Lighting Suitable for use in SnPb or Pb-free soldering processes. z High Power LED Lighting z Low Voltage Industrial Lighting z Indicator and Emergency Lighting z Automotive LED Lighting Simplified Application Circuit L1 D5 VCC C OUT R1 RT8479B D1 D2 R SENSE OVP VCC VL LED+ R2 ISN AC 12V D6 C IN C3 CREG VN LX1 LED- C2 VCOMP D3 D4 L2 LX2 C1 GND Copyright 2014 Richtek Technology Corporation. All rights reserved. is a registered trademark of Richtek Technology Corporation. DS8479B-01 January 2014 www.richtek.com 1+ - RT8479B Marking Information Pin Configurations RT8479BGSP : Product Number (TOP VIEW) RT8479B YMDNN : Date Code 8 GSPYMDNN LX1 LX2 2 7 OVP CREG GND 3 6 GND VCC 9 4 5 VCOMP ISN 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, Ground. The exposed pad must be soldered to a large PCB and connected to GND 9 (Exposed Pad) GND for maximum power dissipation. Compensation Node. A compensation network between VCOMP and GND is 4 VCOMP needed. 5 ISN LED Negative Current Sense Input. Supply Voltage Input. For good bypass, place a ceramic capacitor near the 6 VCC VCC pin. Internal Regulator Output. Place an 1F capacitor between the CREG and 7 CREG GND pins. 8 LX2 Switch Node. The second stage internal MOSFET Drain. Function Block Diagram ISN VCC -130mV Regulator CREG V VCC UV/OV LX2 EN2 EN2 Core OVP Logic EN1 LX1 EN1 VCOMP + GND - Copyright 2014 Richtek Technology Corporation. All rights reserved. is a registered trademark of Richtek Technology Corporation. www.richtek.com DS8479B-01 January 2014 2