DEMO MANUAL DC1205A LT3592: Step-Down 500mA LED Driver with 10:1 Dimming DESCRIPTION Demonstration circuit 1205A features the LT3592 36V step-down 500mA LED driver with 10:1 dimming. The demonstration circuit is designed to drive two red 500mA LEDs mounted on the PCB from a wide input voltage range. The high 2.2MHz switching frequency permits the use of a small inductor and ceramic capacitors to save space and cost. Current mode control provides fast transient response and cycle-by-cycle current limit for short-circuit protection. The LEDs have two brightness settings. With BRIGHT pulled high or left floating, the two red LEDs are driven with 500mA. With BRIGHT pulled to GND, the LED current drops to 50mA for 10:1 analog dimming. The typical efficiency of the LT3592 DC1205A is 85% with 12VIN and the two LEDs at 4.6V total with 500mA as shown in Figure 1. Although the board is stuffed with two red LEDs, different LED strings can be powered from 100 the LT3592. The minimum input voltage to run the stepdown converter at 2.2MHz with a given string of LEDs is shown in Figure 2. The LT3592 data sheet gives a complete description of the part, operation and applications information. The data sheet must be read in conjunction with this Demo Manual for DC1205A. The LT3592 is assembled in a 10-lead plastic DFN (3mm × 2mm) DDB package with a thermally enhanced ground pad. Proper board layout is essential for maximum thermal performance. See the data sheet section Layout Hints. Design files for this circuit board are available at http://www.linear.com/demo L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners. 12 4.6V LED 95 11 10 OUTPUT VOLTAGE (V) EFFICIENCY (%) 90 BRIGHT (500mA) 85 80 75 70 65 9 8 7 6 5 60 4 55 3 50 4 8 12 20 16 INPUT VOLTAGE (V) 24 28 DC1205 F01 Figure 1. Input Voltage vs Efficiency 2 2 4 8 6 10 12 INPUT VOLTAGE (V) 14 16 DC1205 F02 Figure 2. Minimum Input Voltage vs LED Voltage dc1205af 1 DEMO MANUAL DC1205A QUICK START PROCEDURE Demonstration circuit 1205A is easy to set up for evaluating the LT3592 36V step-down 500mA LED driver with 10:1 dimming. Follow the test procedure outlined below and see Figure 3. 3. Tie BRIGHT terminal to GND terminal and observe the LED current dropping to 50mA as brightness also decreases. 4. Use the SHDN terminal to turn the LEDs on and off by respectively floating or grounding the terminal. 1. Set up DC1205A as shown in Figure 3 with hand-held multimeters, and a bench supply (power turned off) with voltage greater than the LED string (approximately 3.5V to 5V) and less than 36V. 2. Turn on the bench power supply and observe a constant 500mA through the string of LEDs with BRIGHT terminal floating. OPTIONAL + A – + + – – V OPTIONAL + V – DC1205 F03 Figure 3. Proper Measurement Equipment Setup dc1205af 2 DEMO MANUAL DC1205A PARTS LIST ITEM QTY REFERENCE PART DESCRIPTION MANUFACTURER/PART NUMBER REQUIRED CIRCUIT COMPONENTS 1 1 C2 Capacitor, X7R, 2.2μF, 50V, 10%, 1206 Murata, GCM31CR71H225KA55 2 1 C3 Capacitor, X7R, 0.1μF, 16V, 10%, 0402 TDK, C1005X7R1C104K 3 1 C4 Capacitor, X5R, 4.7μF, 16V, 10%, 0805 TDK, C2012X5R1C475K 4 1 D1 Diode, Schottky, 1A, POWERDI123 Diode Inc., DFLS140-7-F 6 2 LED2, LED1 LED, Golden Dragon, Red, LED-SFH4230 Osram, LR W5SM-HYJY-1 7 1 L2 Inductor, PWR, 4.7μH, L-CDRH3D18 Sumida, CDRH3D18NP-4R7NC 9 1 R2 Resistor, Chip, 48.7k, 1/16W, 2.2MHz, 1%, 0402 Vishay, CRCW040248K7FKED 10 1 R3 Resistor, 0.4Ω, 1%, 1/4W, 0805 Susumu International USA Inc., RL1220S-R40-F 11 1 R4 Resistor, Chip, 51.1k, 1/16W, 1%, 0402 Vishay, CRCW040251K1FKED 12 1 R5 Resistor, Chip, 10k, 1/16W, 1%, 0402 Vishay, CRCW040210K0FKED 13 1 U1 IC, LT3592EDDB#PBF, DFN10DDB Linear Tech, LT3592EDDB#PBF ADDITIONAL DEMO BOARD CIRCUIT COMPONENTS 8 1 R1 5 7 E1-E7 Resistor, Chip, 100k, 1/16W, 1%, 0402 Vishay, CRCW0402100KFKED HARDWARE FOR DEMO BOARD ONLY TP, Turret, 0.094" Mill-Max, 2501-2-00-80-00-00-07-0 dc1205af 3 A B C E5 E4 E3 E2 E1 C2 2.2uF 50V 1206 1 2 3 R2 48.7k 1% 2.2MHz R1 100k 5% 4 RT BRIGHT SHDN VIN U1 LT3592EDDB 5 4 1. ALL RESISTORS ARE IN OHMS, 0402. ALL CAPACITORS ARE IN MICROFARADS, 0402. NOTE: UNLESS OTHERWISE SPECIFIED GND BRIGHT SHDN GND VIN 6V - 36V 4 VFB OUT CAP DA SW 3 10 9 8 5 6 3 KIM T. DESIGNER: ENGINEER: KEITH S. APPROVED: CHECKED: DRAWN: APPROVALS CONTRACT NO. + 200/20mV _ D1 DFLS140 SUMIDA C3 CDRH3D18 0.1uF L2 16V 4.7uH 1 2 7 BOOST GND 11 0805 R3 0.4 1% 3 E7 E6 GND LED + 1630 McCarthy Blvd. Milpitas, CA 95035 Phone: (408)432-1900 Fax: (408)434-0507 LTC Confidential-For Customer Use Only LED2 LR W5SM RED OSRAM 3 LED1 LR W5SM RED OSRAM 1 DATE: A SIZE 2 1 SHEET DC1205A * LT3592EDDB Wednesday, September 16, 2009 DWG NO. 1 OF 1 A REV STEP-DOWN 500mA LED DRIVER WITH 10:1 DIMMING TECHNOLOGY R5 10k 1% R4 51.1k 1% TITLE: SCHEMATIC C4 4.7uF 16V 0805 2 2 1 2 4 1 D 5 A B C D DEMO MANUAL DC1205A SCHEMATIC DIAGRAM dc1205af DEMO MANUAL DC1205A PCB LAYOUT AND FILM Top Silkscreen Layer 1—Top Layer Layer 2—GND Plane 1 Layer 3—GND Plane 2 dc1205af 5 DEMO MANUAL DC1205A PCB LAYOUT AND FILM Layer 4—Bottom Layer Top Solder Mask Bottom Solder Mask Top Solder Paste Mask dc1205af 6 DEMO MANUAL DC1205A FABRICATION DRAWING dc1205af Information furnished by Linear Technology Corporation is believed to be accurate and reliable. However, no responsibility is assumed for its use. Linear Technology Corporation makes no representation that the interconnection of its circuits as described herein will not infringe on existing patent rights. 7 DEMO MANUAL DC1205A DEMONSTRATION BOARD IMPORTANT NOTICE Linear Technology Corporation (LTC) provides the enclosed product(s) under the following AS IS conditions: This demonstration board (DEMO BOARD) kit being sold or provided by Linear Technology is intended for use for ENGINEERING DEVELOPMENT OR EVALUATION PURPOSES ONLY and is not provided by LTC for commercial use. As such, the DEMO BOARD herein may not be complete in terms of required design-, marketing-, and/or manufacturing-related protective considerations, including but not limited to product safety measures typically found in finished commercial goods. As a prototype, this product does not fall within the scope of the European Union directive on electromagnetic compatibility and therefore may or may not meet the technical requirements of the directive, or other regulations. If this evaluation kit does not meet the specifications recited in the DEMO BOARD manual the kit may be returned within 30 days from the date of delivery for a full refund. THE FOREGOING WARRANTY IS THE EXCLUSIVE WARRANTY MADE BY THE SELLER TO BUYER AND IS IN LIEU OF ALL OTHER WARRANTIES, EXPRESSED, IMPLIED, OR STATUTORY, INCLUDING ANY WARRANTY OF MERCHANTABILITY OR FITNESS FOR ANY PARTICULAR PURPOSE. EXCEPT TO THE EXTENT OF THIS INDEMNITY, NEITHER PARTY SHALL BE LIABLE TO THE OTHER FOR ANY INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES. The user assumes all responsibility and liability for proper and safe handling of the goods. Further, the user releases LTC from all claims arising from the handling or use of the goods. Due to the open construction of the product, it is the user’s responsibility to take any and all appropriate precautions with regard to electrostatic discharge. Also be aware that the products herein may not be regulatory compliant or agency certified (FCC, UL, CE, etc.). No License is granted under any patent right or other intellectual property whatsoever. LTC assumes no liability for applications assistance, customer product design, software performance, or infringement of patents or any other Intellectual property rights of any kind. LTC currently services a variety of customers for products around the world, and therefore this transaction is not exclusive. Please read the DEMO BOARD manual prior to handling the product. Persons handling this product must have electronics training and observe good laboratory practice standards. Common sense is encouraged. This notice contains important safety information about temperatures and voltages. For further safety concerns, please contact a LTC application engineer. Mailing Address: Linear Technology 1630 McCarthy Blvd. Milpitas, CA 95035 Copyright © 2004, Linear Technology Corporation dc1205af 8 Linear Technology Corporation LT 0909 • PRINTED IN USA 1630 McCarthy Blvd., Milpitas, CA 95035-7417 (408) 432-1900 ● FAX: (408) 434-0507 ● www.linear.com © LINEAR TECHNOLOGY CORPORATION 2009