DEMO MANUAL DC1727A LT3641: Dual Monolithic Buck Regulator with Power-On Reset and Watchdog Timer Description Demonstration circuit 1727A is a dual monolithic buck regulator with power-on reset and watchdog timer featuring the LT3641. The board operates from inputs up to 42V and withstands transients up to 55V. The outputs are 5V, 1A and 1.8V, 0.8A. At light loads, both regulators operate in low ripple Burst Mode® to maintain high efficiency and low output ripple. Users can populate R13 on the EN/UVLO pin and R14 on EN2 to provide a programmable under voltage lockout for both outputs respectively. Both channels have cycle-by-cycle current limit, providing protection against shorted outputs. The power-on reset and watchdog timer periods are independently adjustable using external capacitors. Tight accuracy specifications and glitch immunity ensure reliable operation of the circuit. Watchdog can be enabled or disabled by JP1. Performance Summary The circuit can be synchronized to an external clock connected to the SYNC terminal. If the SYNC function is used, the RT resistor (R9) should be chosen to set the LT3641 internal switching frequency at least 20% below the lowest synchronization input frequency. The LT3641 data sheet gives complete descriptions of the part, operation and application information. The data sheet must be read in conjunction with this quick start guide for working on or modifying the demo circuit 1727A. Design files for this circuit board are available at http://www.linear.com/demo L, LT, LTC, LTM, µModule, 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. (TA = 25°C) SYMBOL PARAMETER CONDITIONS VIN Input Supply Range VOUT1 = 5V, IOUT1 = 1A VOUT2 = 1.8V, IOUT2 = 0.8A MIN TYP 7 MAX UNITS 42 V VOUT1 Output Voltage 1 VIN = 12V, IOUT1 = 0.8A 4.92 5.07 5.22 V VOUT2 Output Voltage 2 VIN = 12V, IOUT2 = 1A 1.746 1.8 1.854 V IOUT1 Output Current 1 0 1 A IOUT2 Output Current 2 0 0.8 A IQ No Load Quiescent Current fSW Switching Frequency tWDU Watchdog Upper Boundary Period C7 = 1500pF 55.5 ms tWDL Watchdog Lower Boundary Period C7 = 1500pF 3.5 ms tRST Programmed Reset Period C8 = 1500pF 55.5 ms VIN = 12V, VOUT1 = 5V, VOUT2 = 1.8V, No Load 0.37 1.75 2 mA 2.35 MHz dc1727af 1 DEMO MANUAL DC1727A quick start procedure Demonstration circuit 1727A is easy to set up to evaluate the performance of the LT3641. Refer to Figure 2 for proper measurement equipment setup and follow the procedure below: 1.Place Jumper JP1 in the following position: OFF: Watchdog Disabled ON: Watchdog Enabled 2.With power off, connect the input power supply to VIN and GND. 5.Check for the proper output voltages: VOUT1 = 5V, VOUT2 = 1.8V Note: If there is no output, temporarily disconnect the load to make sure that the load is not set too high or is shorted. 6. Once the proper output voltages are established, adjust the loads within the operating range and observe the output voltage regulation, ripple voltage, efficiency and other parameters. 4.Turn on the power at the input. 7. To test the watchdog timer, place jumper JP1 in the ON position. Connect a clock input to the WDI terminal. Observe the output at the WDO terminal while the clock parameters are adjusted. Note: Make sure that the input voltage does not exceed 42V. 8.To test Power-On Reset, observe output at the RESET terminals: RST1 and RST2. 3.With power off, connect loads from VOUT1 to GND and VOUT2 to GND. 95 2MHz, VIN = 12V VOUT1 = 5V AT 1A, VOUT2 = 1.8V TOTAL EFFICIENCY (%) 90 85 80 75 70 0 0.4 0.6 0.2 VOUT2 CURRENT (A) 0.8 DC1727A F01 Figure 1. Total Efficiency vs VOUT2 Current dc1727af 2 DEMO MANUAL DC1727A Quick Start Procedure Figure 2. DC1727A Proper Measurement Equipment Setup Figure 3. Measuring Input or Output Ripple dc1727af 3 DEMO MANUAL DC1727A Parts List ITEM QTY REFERENCE PART DESCRIPTION MANUFACTURER/PART NUMBER Required Circuit Components 1 1 C1 Capacitor, X7R, 0.22µF, 10V, 10%, 0603 Murata, GRM188R71A224KA01D 2 1 C2 Capacitor, X7R, 4.7µF, 50V, 10%, 1206 Murata, GRM31CR71H475KA12L 3 2 C3, C4 Capacitor, X7R, 22µF, 6.3V, 20%, 1206 AVX, 12066C226MAT2A 4 2 C5, C6 Capacitor, X7R, 1000pF, 25V, 10%, 0603 AVX, 06033C102KAT2A 5 2 C7, C8 Capacitor, COG, 1500pF, 25V, 5%, 0603 Murata, GRM1885C1E152JA 6 1 D1 Diode, Schottky, Diode, SOD323 Central Semiconductor., CMDD6263 7 1 D2 Diode, Schottky, PowerDI123 DIODES/ZETEX, DFLS260-7 8 1 L1 Inductor, 4.7µH Cooper Bussmann, MPI4040R3-4R7-R 9 1 L2 Inductor, 1.0µH Cooper Bussmann, SD3812-1R0-R 10 2 R1, R12 Resistor, Chip, 301k, 1%, 0603 Vishay, CRCW0603301KFKED 11 3 R3, R5, R11 Resistor, Chip, 100k, 1%, 0603 Panasonic, ERJ3EKF1003V 12 1 R7 Resistor, Chip, 49.9k, 1%, 0603 Vishay, CRCW060349K9FKEA 13 1 R9 Resistor, Chip, 32.4k, 1%, 0603 Vishay, CRCW060332K4FKED 14 1 U1 IC, LT3641EFE#PBF, TSSOP (4.4mm) Linear Technology, LT3641EFE#PBF Suncom, 63CE22BS Additional Demo Board Circuit Components 1 1 C9 Capacitor, Aluminum SMT, 22µF, 63V 2 0 C10 (Optional) Capacitor, 0603 3 0 C11 (Optional) Capacitor, 1210 4 0 FB1 (Optional) Ferrite Bead, Chip, 1206 5 0 L3 (Optional) Inductor, SMT Power Inductor 6 5 R2, R4, R6, R8, R10 Resistor, Chip, 100k, 1%, 0603 7 0 R13, R14 (Optional) Resistor, 0603 Vishay, CRCW0603100KFKEA Hardware: For Demo Board Only 1 16 E1-E16 Testpoint, Turret, .095" Mill-Max, 2501-2-00-80-00-00-07-0 2 1 JP1 2mm Single Row Header, 3-Pin Samtec, TMM-103-02-L-S 3 1 JP1 Shunt, 2mm Samtec, 2SN-BK-G 4 4 MTGS Stand-Off, Nylon 0.5" Tall Würth, 702935000 (Snap On) dc1727af 4 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 E10 E9 E15 E13 E6 E12 ON OFF 100K R4 VOUT1R6 JP1 2 R8 WDE 100K 5 2. INSTALL SHUNTS AS SHOWN. 1. ALL RESISTORS ARE IN 0603. ALL CAPACITORS ARE IN 0603. 100K 100K R13 (OPT) R2 NOTE: UNLESS OTHERWISE SPECIFIED RST2 RST1 GND WDO WDI PGOOD2 E4 VOUT1 R11 100K VOUT1 (OPT) 1 3 EN2 R14 E11 4 8 9 13 10 14 2 27 3 RST2 RST1 WDE WDO WDI PGOOD2 EN2 EN/UVLO C7 C8 1500pF 1500pF 11 22 VIN GND CWDT R12 301K C1 0.22uF 10V U1 LT3641EFE RT 7 C2 4.7uF 50V 1206 CPOR 12 20 SW GND R9 32.4K 29 21 GND 23 VIN GND 26 BST GND 1 SYNC SS2 SS1 FB2 FB1 SW2 VIN2 DA SW1 D1 3 4 28 5 1 6 25 24 18 GND VEMI E16 E14 3 THIS CIRCUIT IS PROPRIETARY TO LINEAR TECHNOLOGY AND SUPPLIED FOR USE WITH LINEAR TECHNOLOGY PARTS. JAINO P. APP ENG. 2 SCALE = NONE HZ PCB DES. APPROVALS C10 (OPT) 0603 FB1 1 + C9 22uF 63V OPT VIN SYNC GND VOUT2 1.8V @ 0.8A GND VOUT1 5V @ 1A JAINO P. APPROVED DATE: 1 SHEET 1 LT3641EFE DEMO CIRCUIT 1727A Wednesday, July 13, 2011 IC NO. DATE 7-11-11 OF 1 1 REV. 1630 McCarthy Blvd. Milpitas, CA 95035 Phone: (408)432-1900 www.linear.com Fax: (408)434-0507 LTC Confidential-For Customer Use Only PRODUCTION DESCRIPTION DUAL MONOLITHIC STEP-DOWN SWITCHING REGULATOR WITH POWER-ON RESET AND WATCH DOG TIMER N/A SIZE TITLE: SCHEMATIC C11 (OPT) 1210 OPT L3 LPS4018-332ML R10 100K E8 E7 E5 E3 1 REVISION HISTORY TECHNOLOGY REV VOUT1 E2 __ ECO C4 22uF 6.3V 1206 C3 22uF 6.3V 1206 R7 49.9K R3 100K R1 301K 2 OPTIONAL COMPONENTS C6 1000pF R5 100K L1 4.7uH L2 1.0uH C5 1000pF D2 19 CUSTOMER NOTICE 2 LINEAR TECHNOLOGY HAS MADE A BEST EFFORT TO DESIGN A CIRCUIT THAT MEETS CUSTOMER-SUPPLIED SPECIFICATIONS; HOWEVER, IT REMAINS THE CUSTOMER'S 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 TECHNOLOGY APPLICATIONS ENGINEERING FOR ASSISTANCE. 15 VIN E1 7V -42V TRANSIENT TO 55V GND 16 D 4 GND 17 1 2 5 A B C D DEMO MANUAL DC1727A Schematic Diagram dc1727af 5 DEMO MANUAL DC1727A 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 dc1727af 6 Linear Technology Corporation LT 0711 • PRINTED IN USA 1630 McCarthy Blvd., Milpitas, CA 95035-7417 (408) 432-1900 ● FAX: (408) 434-0507 ● www.linear.com LINEAR TECHNOLOGY CORPORATION 2011