RT8458. High Efficiency PWM Buck LED Driver Controller. Preliminary. General Description. Features. Applications. Pin Configurations

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1 High Efficiency PWM Buck LED Driver Controller General Description The is a PWM controller with an integrated high side floating gate driver. It is used for step down converters by well controlling the external MOSFET and regulating a constant output current. The output duty cycle of the can be up to 100% for wider input voltage application, such as E27 and PAR30 off-line LED lighting products. The also features a 46kHz fixed frequency oscillator, an internal 172mV precision reference, and a PWM comparator with latching logic. The accurate output LED current is achieved by an averaging current feedback loop and the LED current dimming can be easily controlled via the ACTL pin. The also has multiple features to protect the controller from fault conditions, including Under Voltage Lockout (UVLO), Over Current Protection circuit (OCP) and Over Voltage Protection (OVP). Additionally, to ensure the system reliability, a is built with the thermal protection function. The is housed in a tiny SOT23-6 package. Thus, the of components in the whole LED driver system can be made very compact. Ordering Information Package Type E : SOT-23-6 Operating Temperature Range G : Green (Halogen Free with Commercial Standard) Note : Richtek Green products are : RoHS compliant and compatible with the current requirements of IPC/JEDEC J-STD-020. Suitable for use in SnPb or Pb-free soldering processes. Features Low Cost and Efficient Buck Converter Solution Universal Input Voltage Range with Off-Line Topology Programmable Constant LED Current Dimmable LED Current by ACTL Output LED String Open Protection Output LED String Short Protection Output LED String Over Current Protection Built-in Hysteretic Thermal Protection Tiny SOT23-6 Package RoHS Compliant and Halogen Free Applications E27, PAR30, Offline LED Lights Pin Configurations (TOP VIEW) SENSE VC ACTL VCC GND GATE SOT-23-6 Marking Information 01= : Product Code 01=DNN DNN : Date Code 1

2 Typical Application Circuit 10µF µF 3.3k 3.3nF 1 VCC ACTL 3 5 VC SENSE 6 2 GND GATE 4 LED LED- Figure 1. For Typical Application 330nF 1.5M 1.5M 4.7µF/50V C7 C6 3.3nF R4 10k C5 1nF 1 VCC ACTL 3 5 VC SENSE 6 2 GND GATE 4 LED LED- Figure 2. For High PF Application Functional Pin Description Pin No. Pin Name Pin Function 1 VCC Power Supply Pin of the Chip. For good bypass, a ceramic capacitor near the VCC pin is required. 2 GND Ground of the Chip. 3 GATE Gate Driver for External MOSFET Switch. 4 ACTL Analog Dimming Control. The typical effective dimming range is between 0.2V to 1.2V. 5 VC PWM loop Compensation Node. 6 SENSE LED Current Sense Input Pin. Typical sensing threshold is 190mV. 2

3 Function Block Diagram VCC Chip Enable - 16V/7V OVP OSC 35V - S R R 12V 200k GATE - Control Circuit VC Dimming ACTL - SENSE GND 3

4 Absolute Maximum Ratings (Note 1) Supply Input Voltage, V CC V GATE Voltage V ACTL Voltage V VC Voltage V SENSE Voltage V to 6V Power Dissipation, P T A = 25 C SOT W Package Thermal Resistance (Note 2) SOT-23-6, θ JA C/W Junction Temperature C Lead Temperature (Soldering, 10 sec.) C Storage Temperature Range C to 150 C ESD Susceptibility (Note 3) HBM (Human Body Mode) kV MM (Machine Mode) V Recommended Operating Conditions (Note 4) Supply Input Voltage, V CC V to 35V Junction Temperature Range C to 125 C Electrical Characteristics (V CC = 24V DC, C LOAD = 1nF, R LOAD = 2.2Ω in series,t A = 25 C, unless otherwise specified) Parameter Symbol Test Conditions Min Typ Max Unit Input Start-Up Voltage V ST V Input Supply Current I CC After Start-Up, V CC = 24V ma Input Quiescent Current I QC Before Start-Up, V CC = 15V μa Over Voltage Protection V OVP VCC Pin V Current Sense Voltage V SENSE mv Switching Frequency f SW khz Oscillator Maximum Duty Cycle D MAX % Minimum Turn-On Time t ON(MIN) ns Gate Pin Maximum Voltage V Gate V Gate Voltage High Gate Voltage Low V Gate_H V Gate_F I Gate = 20mA I Gate = 100μA I Gate = 20mA I Gate = 100μA GATE Drive Rise and Fall Time 10nF Load at GATE ns GATE Drive Source and Sink Peak Current 10nF Load at GATE A V V To be continued 4

5 LED Dimming Parameter Symbol Test Conditions Min Typ Max Unit Analog Dimming ACTL Pin Input Current LED Current Off Threshold at ACTL I ACTL V ACTL = 0 to 1.3V V ACTL = 0.2V V ACTL_Off V VC Threshold for PWM Switch Off V VC V Thermal Protection Thermal Shutdown Temperature T SD C Thermal Shutdown Recovery T REC C Note 1. Stresses listed as the above "Absolute Maximum Ratings" may cause permanent damage to the device. These are for stress ratings. 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 for extended periods may remain possibility to affect device reliability. Note 2. θ JA is measured in natural convection at T A = 25 C on a low effective thermal conductivity test board of JEDEC 51-3 thermal measurement standard. Note 3. Devices are ESD sensitive. Handling precaution is recommended. Note 4. The device is not guaranteed to function outside its operating conditions. μa 5

6 Outline Dimension D H L C B b A A1 e Symbol Dimensions In Millimeters Dimensions In Inches Min Max Min Max A A B b C D e H L SOT-23-6 Surface Mount Package Richtek Technology Corporation Headquarter 5F, No. 20, Taiyuen Street, Chupei City Hsinchu, Taiwan, R.O.C. Tel: (8863) Fax: (8863) Richtek Technology Corporation Taipei Office (Marketing) 8F, No. 137, Lane 235, Paochiao Road, Hsintien City Taipei County, Taiwan, R.O.C. Tel: (8862) Fax: (8862) marketing@richtek.com Information that is provided by Richtek Technology Corporation is believed to be accurate and reliable. Richtek reserves the right to make any change in circuit design, specification or other related things if necessary without notice at any time. No third party intellectual property infringement of the applications should be guaranteed by users when integrating Richtek products into any application. No legal responsibility for any said applications is assumed by Richtek. 6

7 Datasheet Revision History Version Date Page No. Item Description P /7/29 First Edition P /9/1 General Description Features Typical Application Circuit Functional Pin Description Function Block Diagram Absolute Maximum Ratings Recommended Operating Conditions Electrical Characteristics Modify 7