RT8471 1.2A/1A, Hysteretic, High Brightness LED Driver with Internal Switch General Description Features 7V to 36V Input Voltage Range The RT8471 is a high efficiency, continuous mode inductive Hysteretic Control with High Side Current Sensing step-down converter, designed for driving single or multiple Internal N-MOSFET with 350m Low R DS(ON) series connected LEDs from a voltage source higher than 1A Output Current (For TSOT-23-5 Only) the LED voltage. It operates from an input voltage of 7V to 1.2A Output Current (For SOP-8 (Exposed Pad) and 36V and employs hysteretic control with a high side current MSOP-8 (Exposed Pad) Only) sense resistor to set the constant output current. Up to 97% Efficiency The RT8471 includes an output switch and a high side Typical 5% LED Current Accuracy output current sensing circuit, which uses an external Analog or PWM Control Signal for LED Dimming resistor to set the nominal average output current. LED 300Hz On-Board Ramp Generator brightness control is achieved with PWM dimming from Input Under Voltage Lockout an analog or PWM input signal. Thermal Shutdown Protection The RT8471 is available in a small TSOT-23-5 package or RoHS Compliant and Halogen Free a more thermal efficient SOP-8 (Exposed Pad) and MSOP- 8 (Exposed Pad) packages. Applications Automotive LED Lighting Ordering Information High Power LED Lighting RT8471 Indicator and Emergency Lighting Package Type Architectural Lighting J5 : TSOT-23-5 Low Voltage Industrial Lighting SP : SOP-8 (Exposed Pad-Option 1) Signage and Decorative LED Lighting FP : MSOP-8 (Exposed Pad) Lead Plating System Marking Information G : Green (Halogen Free and Pb Free) (for MSOP-8 (Exposed Pad) and RT8471GJ5 TSOT-23-5 ) 01= : Product Code Z : ECO (Ecological Element with 01=DNN DNN : Date Code Halogen Free and Pb free) (for SOP-8 (Exposed Pad) Only) RT8471ZSP Note : RT8471ZSP : Product Number Richtek products are : RT8471 YMDNN : Date Code RoHS compliant and compatible with the current require- ZSPYMDNN ments of IPC/JEDEC J-STD-020. Suitable for use in SnPb or Pb-free soldering processes. RT8471GFP 0D= : Product Code YMDNN : Date Code 0D=YM DNN Copyright 2013 Richtek Technology Corporation. All rights reserved. is a registered trademark of Richtek Technology Corporation. DS8471-02 December 2013 www.richtek.com 1RT8471 Pin Configurations (TOP VIEW) VIN SENSE 8 VIN GND 5 4 8 SENSE VIN 2 7 SENSE LX 2 GND 7 NC GND GND 3 6 3 6 GND NC GND LX 23 9 9 ADJ 4 5 LX 4 5 ADJ NC LX ADJ GND MSOP-8 (Exposed Pad) TSOT-23-5 SOP-8 (Exposed Pad) Typical Application Circuit V IN 7V to 36V C IN R S RT8471 optional VIN SENSE D ADJ GND L LX Functional Pin Description Pin No. Pin Name Pin Function SOP-8 MSOP-8 TSOT-23-5 (Exposed Pad) (Exposed Pad) 1 7 5, 6 LX Switch Output Terminal. Drain of internal N-MOSFET. Ground. The exposed pad must be soldered to a 3, 8, 2, 3, 2 GND large PCB and connected to GND for maximum 9 (Exposed Pad) 9 (Exposed Pad) power dissipation. Dimming Control Input : 3 4 4 ADJ --- Analog signal input for analog PWM dimming. --- PWM signal input for digital PWM dimming. Output Current Sense. Sense LED string current with 4 2 1 SENSE an external resistor connected between VIN and SENSE. 5 1 8 VIN Supply Input Voltage. -- 5, 6 7 NC No Internal Connection. Copyright 2013 Richtek Technology Corporation. All rights reserved. is a registered trademark of Richtek Technology Corporation. www.richtek.com DS8471-02 December 2013 2