DEMO MANUAL DC1470A LT3743 High Current Synchronous Step-Down LED Driver with Three-State Control DESCRIPTION Demonstration circuit 1470A is a high current synchronous step-down LED driver with three-state control featuring the LT®3743EUFD. The demo board is optimized for 20A output from a 12V input. Being an LED driver, the output current is being regulated until the output voltage reaches a programmed voltage limit. This voltage limit on this demo board is set to around 6V by R5 and R6. The 6V is chosen because of the 6.3V voltage rating of the output capacitors. The ideal load to be used with this demo board is a single LED, such as PT120 from Luminus Devices. Smaller LEDs may not be able to handle the high current, even for a short period of time. At 20A, the demo circuit can operate continuously. However, it is necessary to mount the LED load on a proper heat sink and possibly with a fan to avoid exceeding its maximum temperate rating. Note: The DC470A will drive a LED with its cathode grounded. Grounding cathode of the LED allows customers to use positive input supply. The input voltage range of the LT3743 itself is 6V to 36V. However, the demo board utilizes 30V MOSFETs to demonstrate best efficiency so the maximum recommended input voltage is 24V for the demo board. When input is above 20V during PWM dimming, a slightly larger inductance PERFORMANCE SUMMARY may be needed. The typical efficiency of the demo board is 94% from a 12V input to 5V, 20A load. The lower the input voltage, the higher the efficiency tends to be with a given load. At output power level of 100W, a couple of percent of efficiency improvement is a huge advantage in minimizing temperature rise. If an efficiency measurement is needed in an application, the output voltage must be measured at the output capacitors instead of at the LED load. This prevents cable loss from being counted as a loss of the board. If efficiency measurement is required during PWM dimming, the average current and voltage values should be measured with proper equipment. All LT3743 circuits turn off unnecessary circuits during PWM off period to minimize power losses. As a result, efficiency in many PWM dimming applications is almost the same as efficiency of the constant current applications. The DC1470A uses a split output capacitor configuration to achieve <2μs current rise time from 0A to 20A. To see the real rise time, connecting wires between the LED and the board should be minimized to no more than 2 inches Design files for this circuit board are available at http://www.linear.com/demo/DC1470A 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. Specifications are at TA = 25°C SYMBOL PARAMETER CONDITIONS PVIN* Input Supply Range, PVIN = VIN VOUT* MIN TYP MAX UNITS L1 is Optimized for 12V 12 26.4 V Output Voltage With One PT120 LED, 6V is the Over Voltage Limit 4.5 6 V IOUT Output Current CTRL_SEL > 1V 18.8 20 21.2 A fSW Switching Frequency 400 430 460 kHz IRISE Current Rise Time Following a PWM Rising Edge 2 μs EFF Efficiency at DC VIN = 12V, VOUT = 5V, IOUT = 20A 94 % *PVIN and VIN of the demo circuit are limited to 24V typical by the selection of MOSFETs. The LT3743 input range is 6V to 36V. VOUT maximum of the demo circuit is limited to 6V due to the selection of the output capacitors. dc1470af 1 DEMO MANUAL DC1470A DESCRIPTION total to minimize the wire inductance. 1-inch is even better. The cathode of the LED should return to LED– with R25 populated with a resistor in a few mΩ. It is recommended to measure the voltage on R25 with a short 50Ω coax cable directly into a BNC connector on the oscilloscope. The current can then be calculated from the measured voltage. To get accurate current, R25 should be measured before it is mounted on the board. A current probe adds more delays to the rise time so using a current probe is not recommended. If fast rise time measurement is not necessary, the cathode of the LED can be connected to GND as shown in Figure 1. R27 can be used to slow down the gate drive. Slower gate drive helps to reduce ringing on the SW node without noticeable effect on the efficiency. A 10Ω is usually more than enough to completely damp any ringing. R15, R16 and C15 help filtering out voltage spikes seen on the SENSE+ or SENSE– pin. It is critical to have those components on a board. The LT3743 has a three-state control. It can change output current among zero, a low level and a high level, all in a few μs. The low current level of the demo board is set to around 5A. The high current level is 20A. Both levels can be adjusted by changing the voltage dividers on CTRL_H and CTRL_L. Applying a PWM signal to CTRL_SEL will toggle the output between 5A to 20A. While applying a PWM signal to the PWM pin will toggle the output between either 0A to 5A or 0A to 20A depending on the CTRL_SEL level. The LT3743 data sheet gives a complete description of the part, operation and application information. The data sheet must be read in conjunction with this demo manual for DC1470A. QUICK START PROCEDURE Demonstration circuit 1470A is easy to set up to evaluate the performance of the LT3743. Refer to Figure 1 for proper measurement equipment setup and follow the procedure below: 1.With power off, connect the input power supply to PVIN and GND. The input power supply should have a current limit of 10A or more. 2.With power off, connect a LED between VOUT and GND or between VOUT and LED–, if fast rise time is to be verified. When returning LED to LED–, R25 needs to be populated. To check voltage across R25, the best set up is to solder a short 50Ω coax cable across R25. Connect the other end of the cable directly into a BNC connector on an oscilloscope. A less perfect but easier set up is to touch the probe tip directly across the IS+ and IS– terminals with out the probe ground wire. See Figure 2 for setup. The latter set up tends to have more noise but is ok for non-critical measurements. The LED connecting wires should be as short as possible, 1 inch total being ideal. 4.At this time, the output current will be slightly below 5A. If no output current is observed, turn off PVIN and check the connections. 5.To increase the load current to 20A, turn off PVIN. Pull CTRL_SEL high either by populating R21 or by using an external voltage source. Make sure the load can handle 20A continuously and the load voltage is not too high for the board. Then turn on PVIN. 6.Both the low current level, 5A and the high current level 20A can be adjusted by changing the voltage on CTRL_L and CTRL_H terminals between 0V and 2V. 7.To evaluate the transient between 0A and a non-zero current level, apply a PWM signal to the PWM terminal. The nonzero current level is dictated by the CTRL_SEL and CTRL_H or CTRL_L voltages. 8.To evaluate the transient between two non-zero cur rent levels, apply a PWM signal to the CTRL_SEL terminal. 9. To modify the demo board for other applications, please contact Linear Applications Group for help. 3.Turn on the power at the input. 2 dc1470af DEMO MANUAL DC1470A QUICK START PROCEDURE Figure 1. Proper Measurement Equipment Setup IS– IS+ Figure 2. Measuring Voltage Across R25 dc1470af 3 DEMO MANUAL DC1470A PARTS LIST ITEM QTY REFERENCE PART DESCRIPTION MANUFACTURER/PART NUMBER Required Circuit Components 1 4 C1, C12, C16, C17 CAP., X7R, 4.7μF, 50V, 10%, 1210 MURATA, GRM32ER71H475KA88L 2 1 C2 CAP., X7R, 1μF, 50V, 10%,0805 MURATA, GRM21BR71H105KA12L 3 1 C3 CAP., X7R, 0.22μF, 10V,10%,0603 MURATA, GRM188R71A224KA01D 4 1 C4 CAP., X5R, 22μF, 6.3V, 20%, 0805 MURATA, GRM21BR60J226ME39L 5 6 C5, C6, C18, C21, C23, C25 CAP., POSCAP, 470μF, 6.3V, D4D PANSONIC, 6TPF470MAH 6 1 C7 CAP., C0G, 2nF, 50V, 0603 MURATA, GRM1885C1H202JA01 7 1 C8 CAP., X7R, 1μF, 16V, 10%,0603 MURATA, GRM188R71C105KA12D 8 2 C9,C10 CAP., C0G, 5600pF, 50V, 5% 0603 MURATA, GRM1885C1H562JA01D 9 1 C11 CAP., ALUM., ELECT., 100μF, 50V SUN ELECTRONICS., 50CE100LX 10 1 C15 CAP., X5R, 0.033μF, 50V, 0603 AVX, 06035D333KAT2A 11 1 C26 CAP., X7R, 1200pF, 50V,5%, 0603 AVX, 06035C122JAT2A 12 1 C27 CAP., X7R, 10μF, 25V,10%,1206 MURATA, GRM31CR71E106KA12L 13 1 D1 SCHOTTKY RECTIFIER, 40V, SOD523 NXP SEMI., PMEG4002EB,115 14 1 D2 2.0A LOW VF SCHOTTKY RECTIFIER DIODES INC., DFLS240L-7 15 1 L1 INDUCTOR, 1.3μH WURTH ELECTRONICS, 7443551130 16 2 Q1,Q2 N-CHANNEL MOSFET, LFPAK INFINEON, BSC080N03LS G 17 1 Q3 N-CHANNEL MOSFET, LFPAK INFINEON, BSC011N03LSI 18 2 Q5,Q6 MOSFET, 40V, DUAL N-CHANEL, PPAK VISHAY, Si7234DP 19 1 R1 RES., CHIP, 124k, 1%, 1/W, 0603 VISHAY, CRCW0603124KFKEA 20 1 R2 RES., CHIP, 374k, 1%, 1/W, 0603 VISHAY, CRCW0603374KFKEA 21 1 R3 RES., CHIP, 0.0025Ω, 1W, 1%, 2512 VISHAY, WSL25122L500FEA 22 7 R4, R9, R10, R12, R13, R14, R20 RES., CHIP, 100k, 1%, 1/W, 0603 VISHAY, CRCW0603100KFKEA 23 3 R5, R7, R8 RES., CHIP, 51k, 1%, 1/W, 0603 VISHAY, CRCW060351K0FKEA 24 1 R6 RES., CHIP, 10k, 1%, 1/W, 0603 VISHAY, CRCW060310K0FKEA 25 2 R15, R16 RES., CHIP, 10Ω, 1%, 1/W, 0603 VISHAY, CRCW060310R0FKEA 26 1 R18 RES., CHIP, 24.9k, 1%, 1/W, 0603 VISHAY, CRCW060324K9FKEA 27 1 R19 RES., CHIP, 432k, 1%, 1/W, 0603 VISHAY, CRCW0603432KFKEA 28 1 R23 RES., CHIP, 3.01k, 1%, 1/W, 0603 VISHAY, CRCW06033K01FKEA 29 1 R24 RES., CHIP, 2k, 1%, 1/W, 0603 VISHAY, CRCW06032K00FKEA 30 1 U1 I.C. LT3743EUFD, 28-PIN QFN-4×5 LINEAR TECH., LT3743EUFD#PBF Additional Demo Board Circuit Components 1 0 C13, C14, C19, C20, C22, C24 CAP., D4D, OPT 2 0 R11, R21, R22, R26 RES., OPT, 0603 3 2 R17, R27 RES., CHIP, 0Ω, 0603 4 0 R25 RES., CHIP, 2512, OPT 5 0 Q4 OPT VISHAY, CRCW06030000Z0EA Hardware for Demo Board Only 4 1 10 E1-E8, E13, E14 TURRET, TESTPOINT, 091" MILL MAX 2501-2-00-80-00-00-07-0 2 4 E9-E12 JACK BANANA KEYSTONE, 575-4 3 4 STAND-OFF STAND-OFF, NYLON 0.5" TALL KEYSTONE, 8833(SNAP ON) dc1470af 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. A B C VIN * SYNC CTRL_SEL PWM CTRL_L CTRL_H EN/UVLO GND 6V - 36V E8 E7 E6 E5 E4 E2 E3 E1 5 R9 100K R18 24.9K R10 100K R19 432K R11 OPT R20 100K R12 100K R21 OPT R1 124K R13 100K C7 2nF R2 374K R4 C8 1uF R14 100K (400kHz) R22 OPT 100K C2 1uF 50V VIN 15 8 16 17 18 7 6 4 3 2 28 RT SS SYNC CTRL_SEL PWM CTRL_L CTRL_H CTRL_T VREF EN/UVLO VIN U1 LT3743EUFD 4 23 HG 25 CBOOT VCL VCH PWMGL PWMGH SENSE- SENSE+ LG SW VCC_INT C4 22uF 6.3V VCC_INT C3 0.22uF 13 14 22 19 12 11 R8 51K C15 33nF 3 10 R16 R7 51K 0.0025 R3 + + + C24 OPT C25 470uF Si7234DP Q5 R24 2K A SIZE DATE: IC NO. OPT 1.2nF C26 E14 E13 E11 DATE * IS- IS+ LED- VOUT* GND 6V - 36V PVIN 10-02-09 LT3743EUFD 1 DEMO CIRCUIT 1470A SHEET 3 1 OF 1 REV 1630 McCarthy Blvd. Milpitas, CA 95035 Phone: (408)432-1900 Fax: (408)434-0507 LTC Confidential-For Customer Use Only R6 10k R5 51K E10 E12 E9 C27 10uF Si7234DP Friday, July 31, 2015 THIS CIRCUIT IS PROPRIETARY TO LINEAR TECHNOLOGY AND SUPPLIED FOR USE WITH LINEAR TECHNOLOGY PARTS. 2 APPROVED WALKER B. R25 C20 OPT C21 470uF 1 Q6 8 7 5 6 + TECHNOLOGY + PRODUCTION DESCRIPTION REVISION HISTORY HIGH CURRENT SYNCHRONOUS STEP-DOWN LED DRIVER WITH THREE-STATE CONTROL SCHEMATIC 4 2 C14 OPT C13 OPT 8 7 5 6 C6 470uF C5 470uF C11 100uf,50V 50CE100LX CONTRACT NO. C22 OPT C23 470uF 4 2 + + * 3 1 VIN REV ECO R17 0 LINEAR TECHNOLOGY HAS MADE A BEST EFFORT TO DESIGN A APPROVALS CIRCUIT THAT MEETS CUSTOMER-SUPPLIED SPECIFICATIONS; HOWEVER, IT REMAINS THE CUSTOMER'S RESPONSIBILITY TO PCB DES. ANTONINA K. VERIFY PROPER AND RELIABLE OPERATION IN THE ACTUAL APPLICATION. COMPONENT SUBSTITUTION AND PRINTED ENG. WALKER B. TITLE: CIRCUIT BOARD LAYOUT MAY SIGNIFICANTLY AFFECT CIRCUIT PERFORMANCE OR RELIABILITY. CONTACT LINEAR TECHNOLOGY APPLICATIONS ENGINEERING FOR ASSISTANCE. CUSTOMER NOTICE R23 3.01K VCC_INT C19 OPT C18 470uF C1 C12 4.7uF C16 C17 4.7uF * See Quick Start Guide C9 5.6nF D2 DFLS240 OPT L1 1.3uH BSC080N03LS G Q2 Q1 C10 5.6nF 10 R15 Q3 BSC011N03LSI Q4 OPT 4 26 24 27 D1 PMEG4002EB R27 0 4 R26 OPT 2 1 5 6 7 8 1 2 3 5 6 7 8 1 2 3 D 2 1 3 3 1 3 4 GND 1 GND 5 GND 9 GND 20 GND 21 GND 29 FB 10 5 A B C D DEMO MANUAL DC1470A SCHEMATIC DIAGRAM dc1470af 5 DEMO MANUAL DC1470A 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 6 dc1470af Linear Technology Corporation LT 0915 • PRINTED IN USA 1630 McCarthy Blvd., Milpitas, CA 95035-7417 (408) 432-1900 ● FAX: (408) 434-0507 ● www.linear.com LINEAR TECHNOLOGY CORPORATION 2015