RT8458D High Voltage, High Efficiency, Constant Current PWM Buck Controller for LED Lighting General Description Features zz z zz Low Cost and Efficient Buck Converter Solution The RT8458D is a PWM controller with an internal high zz z zz Input Voltage Depends On External MOSFET side gate driver. Because of the Buck topology, the input zz z zz Programmable Constant LED Current voltage for the Buck system is only limited by the voltage zz z zz Dimmable LED Current by ACTL rating of the external MOSFET. It is used for step down zz z zz 100% Maximum Duty Cycle converters by well controlling the external MOSFET and zz z zz 160kHz Fixed Switching Frequency regulating a constant output current. The output duty cycle zz z zz Output LED String Open Protection of the RT8458D can be up to 100% for wider input voltage zz z zz Output LED String Short Protection application. zz z zz Output LED String Over Current Protection The RT8458D also features a 160kHz fixed frequency zz z zz Built-in Thermal Protection oscillator, an internal 220mV precision reference, and a zz z zz TSOT-23-6 Package PWM comparator with latching logic. The accurate output zz z zz RoHS Compliant and Halogen Free LED current is achieved by an averaging current feedback loop and the LED current dimming can be easily controlled Applications via the ACTL pin. The RT8458D also has multiple features z E27, PAR30, Offline LED Lights to protect the controller from fault conditions, including Under Voltage Lockout (UVLO), Over Current Protection (OCP) and Over Voltage Protection (OVP). Additionally, Marking Information to ensure the system reliability, the RT8458D is built with 13= : Product Code the thermal protection function. 13=DNN DNN : Date Code The RT8458D is housed in a TSOT-23-6 package. Thus, the components in the whole LED driver system can be made very compact. Simplified Application Circuit V IN C IN R VCC D2 RT8458D Analog ACTL VCC Dimming C VCC VC GATE Q1 R VC C GND SENSE VC2 C VC1 R L1 S LED+ C OUT D1 LED- Copyright 2013 Richtek Technology Corporation. All rights reserved. is a registered trademark of Richtek Technology Corporation. DS8458D-06 October 2013 www.richtek.com 1RT8458D Ordering Information Pin Configurations (TOP VIEW) RT8458D Package Type SENSE VC ACTL J6 : TSOT-23-6 6 5 4 Lead Plating System G : Green (Halogen Free and Pb Free) 23 Note : VCC GND GATE Richtek products are : TSOT-23-6 RoHS compliant and compatible with the current require- ments of IPC/JEDEC J-STD-020. Suitable for use in SnPb or Pb-free soldering processes. Functional Pin Description Pin No. Pin Name Pin Function Supply Voltage Input of the chip. For good bypass, a ceramic capacitor near the 1 VCC VCC pin is required. 2 GND Ground of the Chip. 3 GATE Gate Driver Output for External MOSFET Switch. Analog Dimming Control Input. Dimming signal can still be applied to ACTL pin. 4 ACTL ACTL dimming signal high is internally clamped around 1.3V. The sourcing and sinking current should be limited to no more than 10A. 5 VC PWM Loop Compensation Node. LED Current Sense Input. The typical sensing threshold is 220mV between the 6 SENSE SENSE and GND pin. Copyright 2013 Richtek Technology Corporation. All rights reserved. is a registered trademark of Richtek Technology Corporation. www.richtek.com DS8458D-06 October 2013 2