DEMO MANUAL DC2658A LT8643S 42V, 6A Synchronous Step-Down Silent Switcher 2 Description Demonstration circuit 2658A is a 42V, 6A synchronous step-down second generation SILENT SWITCHER with spread spectrum frequency modulation featuring the LT(R)8643S. The demo board is designed for 5V output from a 5.8V to 42V input. The wide input range allows a variety of input sources, such as automotive batteries and industrial supplies. The LT8643S is a compact, ultralow emission, high efficiency, and high speed synchronous monolithic step-down switching regulator. The integrated bypass capacitors optimize all the fast current loops and make it easier to minimize EMI/EMC emissions by reducing layout sensitivity. Selectable spread spectrum mode can further improve EMI/EMC performance. Fast minimum on-time of 30ns enables high VIN to low VOUT conversion at high frequency. The LT8643S switching frequency can be programmed either via oscillator resistor or external clock over a 200kHz to 3MHz range. The default frequency of demo circuit 2658A is 2MHz. The SYNC pin on the demo board is grounded (JP1 at BURST position) by default for low ripple burst mode operation. To synchronize to an external clock, move JP1 to SYNC and apply the external clock to the SYNC terminal. Spread spectrum mode and forced continuous mode can be selected respectively by moving JP1 shunt. Figure 1 shows the efficiency of the circuit at 12V input and 24V input in Burst Mode Operation (input from VIN terminal to bypass the EMI filter). Figure 2 shows Performance Summary SYMBOL PARAMETER VIN_EMI Input Supply Range with EMI Filter VOUT Output Voltage IOUT Maximum Output Current fSW Switching Frequency EFF Efficiency the LT8643S temperature rising on DC2658A demo board under different load conditions. The rated maximum load current is 6A, while derating is necessary for certain input voltage and thermal conditions. The demo board has an EMI filter installed. The EMI performance of the board (with EMI filter) is shown on Figure 3. The red line in Radiated EMI Performance is CISPR25 Class 5 peak limit. The figure shows that the circuit passes the test with a wide margin. To achieve EMI/EMC performance as shown in Figure 3, the input EMI filter is required and the input voltage should be applied at VIN_EMI terminal. An inductor can be added in the EMI filter to further reduce the conducted emission. The EMI filter can be bypassed by applying the input voltage at VIN terminal. The LT8643S 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 DC2658A. The LT8643S is assembled in a 4mm x 4mm LQFN package with exposed pads for low thermal resistance. The layout recommendations for low EMI operation and maximum thermal performance are available in the data sheet section Low EMI PCB Layout and Thermal Considerations and Peak Output Current. Design files for this circuit board are available at http://www.linear.com/demo/DC2658A 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 = 25C CONDITIONS MIN TYP 5.8 4.85 Derating Is Necessary for Certain VIN and Thermal Conditions UNITS 42 V 5.15 V 6 1.85 VIN = 12V , IOUT = 3A 5 MAX A 2 94.2 2.15 MHz % dc2658af 1 DEMO MANUAL DC2658A EFFICIENCY 95 EFFICIENCY (%) 3.5 90 2.5 2.0 80 1.5 POWER LOSS POWER LOSS (W) VIN = 12V VIN = 24V 85 1.0 70 65 100 3.0 90 75 4.0 VOUT = 5V fSW = 2MHz SYNC/MODE = GND 0.5 0 60 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 5.5 6 LOAD CURRENT (A) DC2658A F01 Figure 1. LT8643S DC2658A Efficiency vs Load Current (Input from VIN Terminal) 2 CASE TEMPERATURE RISING (C) 100 80 70 60 50 40 30 20 IOUT = 6A IOUT = 5A IOUT = 4A 10 0 6 12 18 24 30 INPUT VOLTAGE (V) VOUT = 5V fSW = 2MHz 36 42 DC2658A F02 Figure 2. LT8643S DC2658A Case Temperature Rising vs Input Voltage dc2658af DEMO MANUAL DC2658A Conducted EMI Performance 60 50 40 AMPLITUDE (dBV) 30 20 10 0 -10 -20 SPREAD SPECTRUM MODE FIXED FREQUENCY MODE -30 -40 0 3 6 9 12 15 18 FREQUENCY (MHz) 21 24 27 30 DC2658 F03a (WITH EMI FILTER INSTALLED) 14V INPUT TO 5V OUTPUT AT 4A, fSW = 2MHz Radiated EMI Performance (CISPR25 Radiated Emission Test with Class 5 Peak Limits) 50 VERTICAL POLARIZATION PEAK DETECTOR 45 AMPLITUDE (dBV/m) 40 35 30 25 20 15 10 5 CLASS 5 PEAK LIMIT SPREAD SPECTRUM MODE FIXED FREQUENCY MODE 0 -5 0 50 100 200 300 400 500 600 FREQUENCY (MHz) 700 800 900 1000 DC2658 F03b HORIZONTAL POLARIZATION PEAK DETECTOR 45 AMPLITUDE (dBV/m) 40 35 30 25 20 15 10 5 CLASS 5 PEAK LIMIT SPREAD SPECTRUM MODE FIXED FREQUENCY MODE 0 -5 0 100 200 300 400 500 600 FREQUENCY (MHz) (WITH EMI FILTER INSTALLED) 14V INPUT TO 5V OUTPUT AT 4A, fSW = 2MHz 700 800 900 1000 DC2658 F03c Figure 3. LT8643S Demo Circuit DC2658A EMI Performance (14V Input from VIN_EMI, with EMI Filter, IOUT = 4A) dc2658af 3 DEMO MANUAL DC2658A Quick Start Procedure Demonstration circuit 2658A is easy to set up to evaluate the performance of the LT8643S. Refer to Figure 4 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 output voltage ripple by touching the probe tip directly across the output capacitor. See Figure 5 for the proper scope technique. Figure 6 shows the output voltage ripple measured at the output capacitor C9. 1.Place JP1 on BURST position. 2.With power off, connect the input power supply to VIN_EMI and GND. If the input EMI filter is not desired, connect the input power supply to VIN and GND. 3.With power off, connect the load from VOUT to GND. 5.Check for the proper output voltage (VOUT = 5V). 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 voltage is established, adjust the load 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 (JP1 on the SYNC position). Please make sure that R2 should be chose to set the LT8643S switching frequency equal to or below the lowest SYNC frequency. JP1 can also set LT8643S in spread spectrum mode (JP1 on the SPREAD-SPECTRUM position) or forced continuous mode (JP1 on the FCM position). 4.Turn on the power at the input. NOTE: Make sure that the input voltage does not exceed 42V. - POWER - SUPPLY + IIN IOUT + VIN_EMI + - + + + - - VOUT LOAD - Figure 4. Proper Measurement Equipment Setup 4 dc2658af DEMO MANUAL DC2658A Quick Start Procedure Figure 5. Measuring Output Ripple at Output Capacitor C9 VOUT 5mV/DIV AC-COUPLED 500ns/DIV DC2658A F06 Figure 6. LT8643S Demo Circuit DC2658A Output Voltage Ripple (12V Input, IOUT = 6A, Full BW) dc2658af 5 DEMO MANUAL DC2658A Parts List ITEM QTY REFERENCE PART DESCRIPTION MANUFACTURER/PART NUMBER Required Circuit Components 1 2 C2, C12 CAP., X5R, 1F, 50V, 10%, 0603 MURATA, GRM188R61H105KAALD 2 1 C5 CAP., C0G, 330pF, 50V, 5%, 0603 MURATA, GRM1885C1H331JA01D 3 1 C6 CAP., X5R, 100F, 10V, 20% 1210 MURATA, GRM32ER61A107ME20L 4 1 C8 CAP., X7R, 0.1F, 16V, 10%, 0603 MURATA, GRM188R71C104KA01D 5 1 C9 CAP., X5R, 22F, 10V, 20%, 0603 SAMSUNG, CL10A226MPMNUBE 6 1 C16 CAP., C0G, 4.7pF, 50V, 0.1pF, 0603 MURATA, GRM1885C1H4R7BA01D 7 1 C17 CAP., X7R, 10F, 50V, 10%, 1210 MURATA, GRM32ER71H106KA12L 8 1 C20 CAP., X7R, 1F, 10V, 10%, 0603 MURATA, GRM188R71A105KA61D 9 1 L1 INDUCTOR,1.5H COILCRAFT, XEL6030-152ME 10 2 R1, R5 RES., CHIP, 100k, 1/10W, 1% 0603 VISHAY, CRCW0603100KFKEA 11 1 R2 RES., CHIP, 17.8k, 1/10W, 1% 0603 VISHAY, CRCW060317K8FKEA 12 1 R3 RES., CHIP, 243k, 1/10W, 1%, 0603 VISHAY, CRCW0603243KFKEA 13 1 R4 RES., CHIP, 8.45k, 1/10W, 1%, 0603 VISHAY, CRCW06038K45FKEA 14 1 R7 RES., CHIP, 1M, 1/10W, 1%, 0603 VISHAY, CRCW06031M00FKEA 15 1 U1 I.C., STEP-DOWN SWITCHER, 4mm x 4mm LQFN LINEAR TECH., LT8643SEV#PBF Additional Demo Board Circuit Components 1 1 C1 CAP., ALUM 22F, 63V SUN ELECT., 63CE22BS 2 2 C3, C10 CAP., X7R, 10F, 50V, 10%, 1210 MURATA, GRM32ER71H106KA12L 3 2 C14, C21 CAP., X7R, 0.1F, 50V, 10%, 0402 MURATA, GRM155R71H104KE14D 4 0 C15, C18 (OPT) CAP., OPTION, 0603 5 1 FB1 BEAD, FERRITE, 100, 1812 6 0 R6 (OPT) RES., OPTION, 0603 7 1 R8 RES., CHIP, 0, 1/10W, 1%, 0603 VISHAY, CRCW06030000Z0EA WURTH ELEKTRONIK, 74279226101 Hardware: For Demo Board Only 1 8 E1, E5-E9, E11, E14 TESTPOINT, TURRET, .094" MILL-MAX, 2501-2-00-80-00-00-07-0 2 4 E2, E10, E12, E13 TESTPOINT, TURRET, .064" MILL-MAX, 2308-2-00-80-00-00-07-0 3 1 JP1 2x4, 0.079 DOUBLE ROW HEADER WURTH ELEKTRONIK, 62000821121 4 1 XJP1 SHUNT, .079" CENTER WURTH ELEKTRONIK, 60800213421 5 4 J1-J4 JACK BANANA KEYSTONE, 575-4 6 4 MH1-MH4 STAND-OFF, NYLON 0.50" TALL WURTH ELEKTRONIK, 702935000 6 dc2658af A B C D E2 E5 E1 J2 J1 BURST SYNC VIN E9 E14 E7 4 6 8 3 5 7 + C1 22uF 63V 63CE22BS C3 10uF 1210 50V C8 0.1uF C17 10uF 50V 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. 5 1. ALL RESISTORS ARE 0603. ALL CAPACITORS ARE 0603. NOTES: UNLESS OTHERWISE SPECIFIED GND VC TR/SS FCM 2 JP1 C14 0.1uF 0402 50V 1 C21 0.1uF 0402 50V SPREAD-SPECTRUM SYNC VIN GND 5.8V - 42V FB1 74279226101 4 C12 1uF 50V C10 10uF 1210 50V C5 330pF R4 8.45K C2 1uF 50V C15 OPT 22 21 2 20 3 16 5 6 13 14 VC TR/SS VCC SYNC GND GND VIN VIN VIN VIN 100K R1 17 EN VIN_EMI E10 4 GND GND GND GND 25 26 27 28 RT 18 CLKOUT 3 PG FB SW SW SW SW SW BST BIAS OPT R6 R2 17.8K 3 NC NC 4 15 5 19 23 24 8 9 10 11 12 7 1 L1 C18 OPT 1.5uH XEL6030 U1 LT8643SEV 0 R8 R3 243K R7 1M 2 2 C16 4.7pF R5 100K C6 100uF 10V 1210 C20 1uF 10V EN 1 E6 E8 C9 22uF 10V GND VOUT 5V / 6A * CLKOUT PG E13 J4 J3 E12 * SEE DEMO MANUAL E11 1 A B C D DEMO MANUAL DC2658A Schematic Diagram dc2658af 7 DEMO MANUAL DC2658A 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 (c) 2004, Linear Technology Corporation 8 dc2658af LT 0817 * PRINTED IN USA (c) LINEAR TECHNOLOGY CORPORATION 2017