DEMO MANUAL DC1677A LT3988 Dual 60V Step-Down Regulator DESCRIPTION Demonstration circuit 1677A is a dual 60V monolithic 1A step-down regulator featuring the LT®3988. The demo board operates from inputs up to 60V. The outputs are 5V, 1A and 3.3V, 1A. The wide input range of the LT3988 allows a variety of input sources, such as commercial vehicle batteries and industrial supplies. The switching frequency can be programmed either via oscillator resistor or external clock over a 250kHz to 2.5MHz range. When the circuit is synchronized to an external clock connected to the SYNC terminal, the RT resistor (R2) should be chosen to set the LT3988 internal switching frequency within ±25% of the final SYNC frequency. The LT3988 internal boost diodes and loop compensation reduce the components count and solution size. The current mode control scheme creates fast transient response and good loop stability. The EN/UVLO pin can be used to set the part in micropower shutdown mode, reducing the PERFORMANCE SUMMARY PARAMETER supply current to less than 2μA. Users can populate R1 and R3 to provide a programmable undervoltage lockout. Both channels have cycle-by-cycle current limit and diode current sense, providing protection against shorted outputs. The LT3988 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 demo circuit 1677A. The LT3988 is assembled in a 16-lead plastic MSOP package with an exposed pad for low thermal resistance. Proper board layout is essential for both proper operation and maximum thermal performance. See the data sheet section PCB Layout and Thermal Considerations. 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. (TA = 25°C) CONDITIONS VALUE Minimum Input Voltage 7V Maximum Input Voltage 60V Output Voltage VOUT1 VIN = 7V ~ 60V 5V ± 3% Output Voltage VOUT2 VIN = 7V ~ 60V 3.3V ± 3% Switching Frequency RT = 200k 250kHz ± 10% Maximum Output Current IOUT1 VIN = 7V ~ 60V 1A Maximum Output Current IOUT2 VIN = 7V ~ 60V 1A Voltage Ripple VOUT1 VIN = 12V, IOUT1 = 1A < 30mV Voltage Ripple VOUT2 VIN = 12V, IOUT2 = 1A < 30mV dc1677af 1 DEMO MANUAL DC1677A QUICK START PROCEDURE Demonstration circuit 1677A is easy to set up to evaluate the performance of the LT3988. Refer to Figure 2 for proper measurement equipment setup and follow the procedure below: NOTE: When measuring the input or output voltage ripple, care must be taken to avoid a long ground lead on the oscilloscope probe. Measure the input or output voltage ripple by touching the probe tip directly across the VIN or VOUT and GND terminals. See Figure 3 for the proper scope technique. 1. Place JP1 on the ON position and JP2 on the RT position. 2. With power off, connect the input power supply to VIN1 and GND. Also connect the same or another input power supply to VIN2 and GND. 3. With power off, connect loads from VOUT1 to GND and VOUT2 to GND. 4. Turn on the power at the inputs. NOTE: Make sure that the input voltages do not exceed 60V. 5. Check for the proper output voltages: VOUT1 = 5V, VOUT2 = 3.3V. 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 ranges and observe the output voltage regulation, ripple voltage, efficiency and other parameters. 7. An external clock can be added to the SYNC terminal when SYNC function is used (JP2 on the SYNC position). Please make sure that RT should be set to provide a frequency within ±25% of the final SYNC frequency. See the data sheet section Switching Frequency. 90 VOUT1 = 5V 85 80 EFFICIENCY (%) VOUT2 = 3.3V 75 70 65 60 55 50 VIN1 = VIN2 =12V fSW = 250kHz 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 LOAD CURRENT (mA) 0.8 0.9 1 DC1677a F01 Figure 1. Efficiency vs Load Current dc1677af 2 DEMO MANUAL DC1677A QUICK START PROCEDURE + A – + + – A – VIN2 – – + + A – + V VOUT1 + + V + + A + V VIN1 LOAD – V – + VOUT2 – LOAD – DC1677a F02 Figure 2. Proper Measurement Equipment Setup DC1677a F03 Figure 3. Measuring Input and Output Ripple dc1677af 3 DEMO MANUAL DC1677A PARTS LIST ITEM QTY REFERENCE PART DESCRIPTION MANUFACTURER/PART NUMBER Required Circuit Components 1 2 C1, C2 CAP, X7R, 2.2μF 100V, 20%,1210 TDK, C3225X7R2A225M 2 2 C3, C4 CAP, X7R, 1000pF 50V, 5%, 0402 AVX, 04025C102JAT 3 2 C5, C6 CAP, X5R, 0.22μF 16V, 10%, 0603 AVX, 0603YD224KAT 4 1 C8 CAP, C0G, 22pF 16V, 0402, 5% AVX, 0402YA220JAT2A 5 2 C9, C10 CAP, X7R, 47μF 10V, 1210 MURATA, GRM32ER71A476KE15L 6 2 C11, C12 CAP, X5R, 1μF 10V, 10%, 0603 AVX, 0603ZD105KAT2A 7 2 D1, D2 DIODE, SCHOTTKY 1.0A, POWERDI123 DIODE INC, DFLS160L 8 1 L2 IND, 15μH COILCRAFT, XAL5050-153ME 9 1 L1 IND, 22μH COILCRAFT, XAL5050-223ME 10 1 R2 RES, CHIP 200k 0402 VISHAY, CRCW0402200KFKEA 11 1 R4 RES, CHIP 57.6k 1%, 0402 VISHAY, CRCW040257K6FKEA 12 1 R5 RES, CHIP 34k 1%, 0402 VISHAY, CRCW040234K0FKEA 13 1 R7 RES, CHIP 10k 1%, 0402 VISHAY, CRCW040210K0FKEA 14 1 R6 RES, CHIP 10.2k 1%, 0402 VISHAY, CRCW040210K2FKEA 15 1 U1 IC, LT3988EMSE, MS16 LINEAR TECHNOLOGY, LT3988EMSE#PBF SUNCON, 100CE22BS Additional Circuits 16 0 C13, C14 (OPT) CAP, ALUM, 22μF 20% 100V, CE-BS 17 0 C7 (OPT) CAP, 0402 18 0 R1, R3 (OPT) RES, CHIP 0603 Hardware (For Demo Board Only) 19 12 E1 TO E12 TESTPOINT, TURRET, 0.095" MILL-MAX, 2501-2-00-80-00-00-07-0 20 2 JP1, JP2 2mm SINGLE ROW HEADER, 3 PIN SAMTEC, TMM-103-02-L-S 21 2 JP1, JP2 SHUNT SAMTEC, 2SN-BK-G dc1677af 4 B A E1 E8 E2 E6 E5 C9 47uF 10V 1210 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. 2. INSTALL SHUNTS AS SHOWN. 1. ALL RESISTORS ARE IN 0402. ALL CAPACITORS ARE IN 0402. 22uH D1 DFLS160L L1 RT 2 OFF ON SYNC JP2 C1 JP1 2.2uF 2 100V 1210 R3 (OPT) 1% 0603 C13 22uF 100V OPT C11 1uF 10V 0603 + VIN1 1 3 1 14 1 2 3 12 15 5 16 FB1 DA1 SW1 BOOST1 SYNC THIS CIRCUIT IS PROPRIETARY TO LINEAR TECHNOLOGY AND SUPPLIED FOR USE WITH LINEAR TECHNOLOGY PARTS. VIN2 SCALE = NONE YING C. HZ APPROVALS FB2 DA2 SW2 BOOST2 BD RT TRACK/SS2 LT3988EMSE TRACK/SS1 EN/UVLO VIN1 CUSTOMER NOTICE R6 10.2K 1% R4 57.6k C7 (OPT) C5 0.22uF 0603 C3 1nF R1 (OPT) 1% 0603 U1 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 APP ENG. APPLICATION. COMPONENT SUBSTITUTION AND PRINTED CIRCUIT BOARD LAYOUT MAY SIGNIFICANTLY AFFECT CIRCUIT PERFORMANCE OR RELIABILITY. CONTACT LINEAR TECHNOLOGY APPLICATIONS ENGINEERING FOR ASSISTANCE. NOTE: UNLESS OTHERWISE SPECIFIED GND VOUT1 5V / 1A SYNC E11 TRACK/SS1 EN/UVLO GND 7V - 60V 1 3 E7 1 2 VIN1 GND 17 R7 10k C6 0.22uF 0603 R2 200K 1% 2 REV R5 C8 DATE: N/A SIZE DESCRIPTION TECHNOLOGY 34k 22pF D2 DFLS160L L2 15uH C12 1uF 10V 0603 + E4 E3 GND VOUT2 3.3V / 1A E12 TRACK/SS2 7V - 60V C14 22uF 100V OPT E10 GND 2 Thursday, March 22, 2012 IC NO. SHEET 1 OF 1 2 REV. 1630 McCarthy Blvd. Milpitas, CA 95035 Phone: (408)432-1900 www.linear.com Fax: (408)434-0507 LTC Confidential-For Customer Use Only C10 47uF 10V 1210 C2 2.2uF 100V 1210 DATE 11-9-11 E9 VIN2 YING C. APPROVED REVISION HISTORY PRODUCTION C4 1nF 2 DUAL 60V STEP-DOWN REGULATOR LT3988EMSE DEMO CIRCUIT 1677A TITLE: SCHEMATIC 11 8 7 6 4 13 10 9 __ ECO 1 2 1 B A DEMO MANUAL DC1677A SCHEMATIC DIAGRAM dc1677af 5 DEMO MANUAL DC1677A 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 dc1677af 6 Linear Technology Corporation LT 0612 • PRINTED IN USA 1630 McCarthy Blvd., Milpitas, CA 95035-7417 (408) 432-1900 ● FAX: (408) 434-0507 ● www.linear.com © LINEAR TECHNOLOGY CORPORATION 2012