DEMO MANUAL DC1602A LT3741 High Power Constant Current, Constant Voltage Synchronous Buck Controller Description Demonstration circuit 1602A is a high power constant current, constant voltage synchronous buck controller featuring the LT®3741. 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. The voltage limit on this demo board is set to around 6V by R11 and R14. The 6V is chosen because of the 10V voltage rating of the output capacitors. Higher output voltage can be easily achieved with higher voltage rated 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. The input voltage range of the LT3741 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. 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. Output current can be adjusted by varying the CTRL1 voltage. R16 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. R10, R13 and C14 help filtering out voltage spikes seen on the SENSE+ or SENSE– pin. It is critical to have those components on a board. The LT3741 data sheet gives a complete description of the part, operation and application information. The data sheet must be read in conjunction with this quick start guide for demo circuit 1602A. Design files for this circuit board are available at http://www.linear.com/demo/DC1602A. 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. Performance Summary Specifications are at TA = 25°C SYMBOL PARAMETER CONDITIONS TYP MAX PVIN* Input Supply Range. PVIN = VIN L1 is Optimized for 12V. 12 24 V VOUT* Output Voltage With ONE PT120 LED. 6V Is the Overvoltage Limit 4.5 6 V IOUT Output Current In Current Mode 18.8 20 21.2 A VOUT Output Voltage In Voltage Mode 5.88 6 6.12 V FSW Switching Frequency R3 = 100k 380 420 460 kHz EFE Efficiency at DC VIN = 12V, VOUT = 5V, IOUT = 20A MIN UNITS 94 % * PVIN and VIN of the demo circuit are limited to 24V typical by the selection of MOSFETs. The LT3741 input range is 6V to 36V. VOUT maximum of the demo circuit is limited to 6V due to the selection of the output capacitors. dc1602af 1 DEMO MANUAL DC1602A Quick Start Procedure Demonstration circuit 1602A is easy to set up to evaluate the performance of the LT3741. 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. 3. Turn on the power at the input. Be careful not to look at a powered LED directly. 4. Carefully evaluate other design parameters as needed. 5. Adjust CTRL1 to change output current. 6. To modify the demo board for other applications, please contact Linear Applications Group for help. – LOAD + DC1602 F01 Figure 1. Proper Measurement Equipment Setup 2 dc1602af DEMO MANUAL DC1602A Parts List ITEM QTY REFERENCE PART DESCRIPTION MANUFACTURER/PART NUMBER Required Circuit Components 1 1 C1 CAP., ALUM., ELECT., 100µF, 50V SUN ELECT., 50CE100LX 2 4 C2, C3, C4, C5 CAP., X7R, 4.7µF, 50V, 10%, 1210 MURATA, GRM32ER71H475KA88L 3 2 C8, C10 CAP., POSCAP, 150µF, 10V SANYO, 10TPF150ML 4 1 C6 CAP., X7R, 1µF, 50V, 10%, 0805 MURATA, GRM21BR71H105KA12L 5 1 C7 CAP., X7R, 0.22µF, 10V, 10%, 0603 MURATA, GRM188R71A224KA01D 6 2 C9, C11 CAP., X5R, 47µF, 16V, 10%, 1210 MURATA, GRM32ER61C476KE15L 7 1 C12 CAP., X5R, 22µF, 6.3V, 20%, 0805 MURATA, GRM21BR60J226ME39L 8 1 C13 CAP., COG, 2nF, 50V, 0603 MURATA, GRM1885C1H202JA01D 9 1 C14 CAP., NPO, 33nF, 16V, 0603 MURATA, GRM188R71C333KA01D 10 1 C15 CAP., X7R, 10000pF, 16V, 0603 MURATA, GRM188R71C103KA01D 11 1 C17 CAP., U2J, 5100pF, 50V, 0603 MURATA, GRM1887U1H512JA01D 12 1 D1 1.0A LOW VF SCHOTTKY RECTIFIER DIODES INC., DFLS140 13 1 D2 2.0A LOW VF SCHOTTKY RECTIFIER DIODES INC., DFLS240L 14 1 L1 INDUCTOR, 1.3µH WE., 7443551130 15 2 Q1, Q2 MOSFET, N-CHANNEL, PG-TDSON-8 INFINEON, BSC080N03LS G 16 1 Q3 MOSFET, N-CHANNEL, PG-TDSON-8 INFINEON, BSC011N03LSI 17 1 R1 RES., CHIP, 374k, 1%, 0603 VISHAY, CRCW0603374KFKEA 18 1 R2 RES., CHIP, 124k, 1%, 0603 VISHAY, CRCW0603124KFKEA 19 3 R3, R5, R8 RES., CHIP, 100k, 1%, 0603 VISHAY, CRCW0603100KFKEA 20 1 R4 RES., CHIP, 0.0025, 1W, 1%, 2512 VISHAY, WSL25122L500FEA 21 1 R7 RES., CHIP, 45.3k, 1%, 0603 VISHAY, CRCW060345K3FKEA 22 2 R10, R13 RES., CHIP, 10Ω, 1%, 0603 VISHAY, CRCW060310R0FKEA 23 1 R11 RES., CHIP, 40.2k, 1%, 0603 VISHAY, CRCW060340K2FKEA 24 1 R12 RES., CHIP, 680k, 1%, 0603 VISHAY, CRCW0603680KFKEA 25 1 R14 RES., CHIP, 10k, 1%, 0603 VISHAY, CRCW060310K0JNEA 26 1 R15 RES., CHIP, 66.5k, 1%, 0603 VISHAY, CRCW060366K5FKEA 27 1 U1 I.C. LT3741EFE, 20-PIN TSSOP LINEAR TECH., LT3741EFE#PBF dc1602af 3 DEMO MANUAL DC1602A Parts List ITEM QTY REFERENCE PART DESCRIPTION MANUFACTURER/PART NUMBER Additional Demo Board Circuit Components 1 0 C16, C18 CAP., 0603, OPT 2 0 Q4 MOSFET, OPT 3 1 R16 RES., CHIP, 0Ω, 0603 4 0 R9, R17 RES., 1206, OPT VISHAY, CRCW06030000Z0ED Hardware: For Demo Board Only 1 4 E1, E2, E4, E5 JACK, BANANA KEYSTONE, 575-4 2 6 E3, E6, E7, E8, E9, E10 TURRET, TESTPOINT , 091" MILL MAX 2501-2-00-80-00-00-07-0 3 4 STAND-OFF STAND-OFF, NYLON, 0.5" tall KEYSTONE, 8833(SNAP ON) 4 dc1602af 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 D VIN * CTRL2 CTRL1 SYNC EN/UVLO GND GND 6V - 36V E7 E6 E8 E3 E9 5 E2 E1 R2 124K C1 100uF,50V 50CE100LX R12 680K R7 45.3K C2 C3 4.7uF 1210 C15 10nF R8 100K C17 5nF R9 OPT R5 100K R3 100K - SEE QUICK START GUIDE 1. ALL RESISTORS ARE IN OHMS, 0603. ALL CAPACITORS ARE IN MICROFARADS, 0603. * 4 NOTE: UNLESS OTHERWISE SPECIFIED C13 2nF R1 374K VIN + 4 C6 1uF 50V 0805 VC SS CTRL2 CTRL1 VREF SYNC RT EN/UVLO R15 66.5K 13 9 6 8 5 15 14 4 LT3741EFE U1 C4 C5 4.7uF 1210 VIN FB SENSEN SENSEP LG SW VCC_INT CBOOT HG 10 12 11 20 18 1 19 17 D1 DFLS140 C18 OPT 3 THIS CIRCUIT IS PROPRIETARY TO LINEAR TECHNOLOGY AND SUPPLIED FOR USE WITH LINEAR TECHNOLOGY PARTS. 2 2 SCALE = NONE C9 C11 47uF 1210 __ ECO 2-1 2 DESCRIPTION R14 10k C8 C10 150uF OPT C16 GND GND 20A @ 6V VOUT * 1-6-16 WALKER B. WALKER B. DATE 02-02-10 APPROVED DATE: N/A SIZE 1 DEMO CIRCUIT 1602A Thursday, January 07, 2016 IC NO. SHEET 1 2-1 OF 1 REV. HIGH POWER CONSTANT CURRENT, CONSTANT VOLTAGE SYNCHRONOUS BUCK CONTROLLER LT3741EFE 1630 McCarthy Blvd. Milpitas, CA 95035 Phone: (408)432-1900 www.linear.com Fax: (408)434-0507 LTC Confidential-For Customer Use Only R11 40.2K E10 E5 E4 REBUILD CHANGED Q1,Q2,Q3 PRODUCTION 1 REVISION HISTORY TECHNOLOGY REV TITLE: SCHEMATIC R4 0.0025 2512 WALKER B. A.K. APPROVALS L1 1.3uH WE 7443551130 D2 DFLS240L R17 OPT 1206 CUSTOMER NOTICE R13 10 R10 10 4 C12 22uF 0805 VIN LINEAR TECHNOLOGY HAS MADE A BEST EFFORT TO DESIGN A CIRCUIT THAT MEETS CUSTOMER-SUPPLIED SPECIFICATIONS; HOWEVER, IT REMAINS THE CUSTOMER'S RESPONSIBILITY TO PCB DES. VERIFY PROPER AND RELIABLE OPERATION IN THE ACTUAL APPLICATION. COMPONENT SUBSTITUTION AND PRINTED APP ENG. CIRCUIT BOARD LAYOUT MAY SIGNIFICANTLY AFFECT CIRCUIT PERFORMANCE OR RELIABILITY. CONTACT LINEAR TECHNOLOGY APPLICATIONS ENGINEERING FOR ASSISTANCE. C14 33nF 4 C7 0.22uF Q3 BSC011N03LSI Q4 OPT R16 0 Q1 Q2 BSC080N03LS G 3 2 1 3 VIN 21 GND 16 7 GND 2 GND GND 2 1 5 6 7 8 1 2 3 5 6 7 8 1 2 3 5 A B C D DEMO MANUAL DC1602A Schematic Diagram dc1602af 5 DEMO MANUAL DC1602A 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 dc1602af Linear Technology Corporation LT 0416 • PRINTED IN USA 1630 McCarthy Blvd., Milpitas, CA 95035-7417 (408) 432-1900 ● FAX: (408) 434-0507 ● www.linear.com © LINEAR TECHNOLOGY CORPORATION 2016