DEMO MANUAL DC736A LT3724 High Voltage Current Mode Step-Down Converter Description Demonstration Circuit 736A is a 200kHz high voltage, current-mode DC/DC step-down converter featuring the LT®3724. The circuit operates from a VIN range of 30V to 55V and outputs 24V at 3A (72W). A soft-start feature controls the output voltage slew rate at start-up, reducing current surges and voltage overshoots. Burst Mode® operation that improves the efficiency at light loads can be enabled with a jumper. An optional boost bias circuit is provided on the bottom side of the board for back-driving the LT3724 internal regulator from the output voltage. Customers might want to use this optional circuit with modified applications that have relatively high input voltages and low (~5V) output voltages. In such applications, the optional circuit can increase the overall efficiency by reducing the power lost Performance Summary PARAMETER This circuit is suitable for a wide range of Industrial control systems and particularly suitable for 12V/42V automotive applications and 48V Telecom power supplies. The LT3724 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. Design files for this circuit board are available at http://www.linear.com/demo L, LT, LTC, LTM, Linear Technology, the Linear logo and Burst Mode are registered trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners. Specifications are at TA = 25°C CONDITIONS Input Voltage Range Efficiency in the LT3724. The demonstration circuit has also been layed out with the option for a second switching MOSFET to facilitate higher output currents. The circuit design can be modified for a boost converter configuration. MIN TYP 30 VIN = 30V, IOUT = 3.0A VIN = 48V, IOUT = 3.0A VIN = 55V, IOUT = 3.0A Switching Frequency MAX 55 UNITS V 97.4 95.4 94.7 % % % 200 kHz Output Voltage IOUT = 0A to 3.0A 24 V Output Voltage Ripple VIN = 48V, IOUT = 3.0A 100 mV dc736af 1 DEMO MANUAL DC736A Quick Start Procedure DC736A is easy to set up to evaluate the performance of the LT3724. Refer to Figure 1 for proper measurement equipment setup and follow the procedure below: 5.Turn on the power at the input and adjust the input voltage until the LT3724 turns on. NOTE: Make sure that the input voltage does not exceed 55V. NOTE: When measuring the input or output voltage ripple, care must be taken to avoid a long ground lead on the oscilloscope probe. See Figure 2 for the proper scope technique. 6.Check for the proper output voltage. NOTE: If there is no output, temporarily disconnect the load to make sure that the load is not set too high or is shorted. 1.Place JP1 in the RUN position. 2.Place JP2 in the desired operating mode: fixed frequency or Burst Mode operation. 7.Once the proper output voltage is established, adjust the input voltage and load within the operating range and observe the output voltage regulation, ripple voltage, efficiency and other parameters. 3.With power off, connect the input power supply to VIN and GND. 4.With power off, connect the load to VOUT and GND. 55V Power Supply + – – LOAD – + – + + Figure 1. Proper Measurement Equipment Setup + VOUT – COUT GND Figure 2. Measuring Output Ripple dc736af 2 DEMO MANUAL DC736A Parts List ITEM QTY REFERENCE PART DESCRIPTION MANUFACTURER/PART NUMBER 1 1 CIN1 Cap., Aluminum 68µF 63V 20% Sanyo 63MV68AX-T 2 2 CIN2, CIN3 Cap., X7R 2.2µF 100V 20% TDK C4532X7R2A225M 3 1 COUT1 Cap., Alum 330µF 35V 10% Sanyo 35CV330AX-T 4 2 COUT3, COUT2 Cap., X7R 22µF 25V 20% TDK C5750X7R1E226M 5 1 C1 Cap., NPO 1000pF 100V 10% AVX 08051A102KAT1A 6 1 C2 Cap., X5R 0.22µF 16V 10% Taiyo Yuden EMK107BJ224KA 7 1 C3 Cap., X7R 1000pF 25V 10% AVX 04023C102KAT2A 8 1 C4 Cap., X5R 0.1µF 16V 10% AVX 0402YD104KAT2A 9 1 C5 Cap., X5R 1µF 16V 10% Taiyo Yuden EMK212BJ105KG 10 1 C6 Cap., X7R 120pF 25V 10% AVX 04023C121KAT2A 11 1 C7 Cap., X7R 1500pF 16V 20% 0402 AVX 0402YC152MAT2A 12 1 C12 Cap., X7R 0.01µF 16V 10% AVX 0402YC103KAT2A 13 1 D1 Diode, Speed Switching Diodes Inc. BAS19 14 1 D2 Schottky Diode 60V IR 30BQ060 15 1 D5 Diode, 75V/200mW Diodes Inc. 1N4148WS 16 1 L1 Inductor, 47µH Coilcraft DO5040H-473MLB 17 1 Q1 MOSFET N-Channel, PowerPak SO8 Vishay Siliconix Si7852DP 18 1 R1 Res, Chip 1M 0.1W 5% AAC CR10-105JM 19 1 R2 Res/Jumper, Chip 0Ω 0.06W 1A AAC CJ05-000M 20 1 R3 Res., Chip 52.3k 1/16W 1% Vishay CRCW0402 52.3K 1% 21 1 R4 Res., Chip 402K 1/16W 1% AAC CR05-4023FM 22 1 R5 Res., 0.025 0.5W 1% IRC LRF2010-01-R025-F 23 1 R6 Res., Chip 1M 0.1W 5% AAC CR16-105JM 24 1 R7 Res., Chip 4.99k 0.06W 1% AAC CR05-4991FM 25 1 R8 Res., Chip 93.1k 1/16W 1% AAC CR05-9312FM 26 1 R9 Res., Chip 2.21k 1/16W 1% AAC CR05-2211FM 27 1 R14 Res., Chip 470 1/16W 5% AAC CR05-471JM 28 1 R15 Res., Chip 47k 1/16W 5% AAC CR05-473JM 29 1 U1 I.C., Voltage Regulator Linear Technology Corporation LT3724EFE Additional Demo Board Circuit Components 1 0 C8 Cap., X5R C-4.7µF, 6.3V-0805 6.3V 20% Taiyo Yuden JMK212BJ475MG-T 2 0 C9 Cap., X5R 1µF 16V 20% Taiyo Yuden EMK212BJ105MG 3 0 C10 Cap., NPO 220pF 25V 10% AVX 04023A221KAT2A 4 0 C11 Cap., Aluminum 22µF 35V 10% Sanyo 35MV22UAX 5 0 D3,D4 Schottky Diode, 40V Zetex ZHCS400 6 0 L2 Inductor, L-10µH Murata LQH3C100M24 7 0 R10 Res./Jumper, Chip 0Ω 0.06W 1A AAC CJ05- 000M 8 0 R11 Res., Chip 107k 0.06W 1% AAC CR05-1073FM 9 0 R12 Res., Chip 10k 0.06W 5% AAC CR05-103JM 10 0 R13 Res., Chip 12.4k 1/16W 1% AAC CR05-1242FM 11 0 U2 I.C., Voltage Regulator Linear Technology Corporation LT1613CS5 dc736af 3 DEMO MANUAL DC736A Parts List ITEM QTY REFERENCE PART DESCRIPTION MANUFACTURER/PART NUMBER Hardware – For Demo Board Only 1 4 E1, E2, E3, E4 Testpoint, Turret Mill Max 2501-2 2 0 E5 Testpoint, Turret Mill Max 2501-2 3 2 JP2, JP1 Headers, 3 Pins 2mm Ctrs. Comm Con Connectors 2802S-03G2 4 2 XJP1, XJP2 JMP, 3 Pin 1 Row .079CC Comm Con Connectors CCIJ2MM-138GW dc736af 4 DEMO MANUAL DC736A Schematic Diagram B A VCC 1 2 3 C9 1µF + 4 VIN CIN1 68µF GND 63V 100V CIN3 C12 JP1 0.01µF R14 470 SHDN RUN 2.2µF CIN2 2.2µF 100V BURST_EN R6 1M 0603 R7 4.99k 1% D3 ZHCS400 3 1 R1 1M 0805 2 SHDN 3 R8 93.1k 1% R15 47k D5 1N4148WS L2 5 10µH 1 VIN SHDN SW FB R3 52.3k 1% C3 C1 1000pF 100V R4 VOUT C8 0805 4.7µF,6.3V C6 120pF VC VFB 402k 1% C7 1500pF R9 2.21k 1% 1000pF 10% U2 LT1613CS5 4 OPTIONAL BOOST BIAS CIRCUIT (DO NOT INSTALL) C10 220pF R11 107k 1% R12 10k 2 GND 3 3 1 2 3 4 5 6 7 8 NC NC SW TG BOOST SHDN VIN U1 LT3724EFE CSS 35V (Opt) 22µF C11 D4 ZHCS400 (Opt) SENSE- SENSE+ PGND BURST_EN VCC VFB VC GND VCC + 16 15 R2 0 Ohm 14 SW 13 12 C2 10% 0.22µF C4 D1 BAS19 10% 11 10 0.1µF 9 E5 VBIAS 9V-20V (Opt) VIN VCC C5 1µF 10% 2 47µH L1 0.025 1% 0.5W R5 Q1 Si7852DP DO5040H-473MLB COILCRAFT D2 30BQ060 + 330µF COUT1 35V 1 VOUT COUT3 22µF COUT2 25V 22µF 25V 1 VOUT GND STAND-OFF LTC CONFIDENTIAL - For Customer Use Only 2 E3 VOUT 24V @ 3A E4 GND B A 5 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. This circuit is proprietary to Linear Technology and supplied for use with Linear Technology parts. Customer Notice: Linear Technology has made a best effort to design a circuit that meets customer-supplied specifications; however, it remains the customers responsibility to verify proper and reliable operation in the actual application, Component substitution and printed circuit board layout may significantly affect circuit performance or reliability. Contact Linear Applications Engineering for assistance. E1 E2 JP2 VIN 30V - 55V GND FIXED FREQ. BURST MODE VCC R10 0 Ohm 16V R13 12.4k 1% 4 Sgnd 17 dc736af DEMO MANUAL DC736A 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 dc736af 6 Linear Technology Corporation LT 0912 • PRINTED IN USA 1630 McCarthy Blvd., Milpitas, CA 95035-7417 (408) 432-1900 ● FAX: (408) 434-0507 ● www.linear.com LINEAR TECHNOLOGY CORPORATION 2012