DEMO MANUAL DC2202A LT8640 42V, 5A Micropower Synchronous Step-Down Silent Switcher Description Demonstration circuit 2202A is a 42V, 5A micropower synchronous step-down Silent Switcher® with spread spectrum frequency modulation featuring the LT®8640. The demo board is designed for 5V output from a 5.7V to 42V input. The wide input range allows a variety of input sources, such as automotive batteries and industrial supplies. The LT8640 is a compact, ultralow emission, high efficiency, and high speed synchronous monolithic step-down switching regulator. The integrated power switches and inclusion of all necessary circuitry reduce the components count and solution size. Special Silent Switcher architecture minimizes EMI/EMC emissions. Selectable spread spectrum mode can further improve EMI/EMC performance. Ultralow 2.5μA quiescent current in Burst Mode® operation achieves high efficiency at very light loads. Fast minimum on-time of 40ns enables high VIN to low VOUT conversion at high frequency. The LT8640 switching frequency can be programmed either via oscillator resistor or external clock over a 200kHz to 3MHz range. 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 turret. Spread spectrum mode and pulse-skipping mode can be selected respectively by moving JP1 shunt. Figure 1 shows the efficiency of the circuit at 12V and 24V input in Burst Mode operation (input from VIN turret pin). Figure 2 Performance Summary SYMBOL VIN VOUT IOUT PARAMETER Input Supply Range Output Voltage Maximum Output Current fSW EFE Switching Frequency Efficiency at DC shows the LT8640 temperature rising on DC2202A demo board under different load conditions. The rated maximum load current is 5A, 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 Figure 3 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 VEMI turret pin. An inductor L2, which is a 0Ω jumper on the board by default now, can be added in the EMI filter to further reduce the conducted emission. The LT8640 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 2202A. The LT8640 is assembled in a 3mm × 4mm plastic QFN package with exposed pads for low thermal resistance. Proper board layout is essential for both low EMI operation and maximum thermal performance. See the data sheet sections 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/DC2202A L, LT, LTC, LTM, Linear Technology, the Linear logo, Burst Mode and Silent Switcher are registered trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners. Specifications are at TA = 25°C CONDITIONS Derating Is Necessary for Certain VIN and Thermal Conditions VIN = 12V , IOUT = 3A MIN 5.7 4.85 5 TYP 1.85 2 93.7 5 MAX 42 5.15 UNITS V V A 2.15 MHz % dc2202af 1 DEMO MANUAL DC2202A Quick Start Procedure 100 100 VIN = 12V EFFICIENCY (%) 90 VIN = 24V 85 80 75 70 VOUT = 5V fSW = 2MHz SYNC/MODE = GND 65 60 0.5 1 1.5 2 2.5 3 3.5 4 LOAD CURRENT (A) IOUT = 5A IOUT = 4.5A IOUT = 4A IOUT = 3.5A 90 TEMPERATURE RISING (°C) 95 4.5 80 70 60 50 40 30 VOUT = 5V fSW = 2MHz 20 10 5 6 12 18 24 30 INPUT VOLTAGE (V) 35 42 DC2202A F02 DC2202A F01 Figure 1. LT8640 Demo Circuit DC2202A Efficiency vs Load Current (Input from VIN Turret Pin) Figure 2. LT8640 Demo Circuit DC2202A Temperature Rising vs Input Voltage 50 VERTICAL POLARIZATION PEAK DETECTOR 45 AMPLITUDE (dBµV/m) 40 35 30 25 20 15 10 5 CLASS 5 PEAK LIMIT BURST MODE SPREAD SPECTRUM MODE 0 –5 0 100 200 300 400 500 600 700 800 900 1000 FREQUENCY (MHz) 50 HORIZONTAL POLARIZATION PEAK DETECTOR 45 AMPLITUDE (dBµV/m) 40 35 30 25 20 15 10 5 CLASS 5 PEAK LIMIT BURST MODE SPREAD SPECTRUM MODE 0 –5 0 100 200 300 400 500 600 700 800 900 1000 FREQUENCY (MHz) DC2202A DEMO BOARD (WITH EMI FILTER INSTALLED) 14V INPUT TO 5V OUTPUT AT 4A, fSW = 2MHz DC2202A F03 Figure 3. LT8640 Demo Circuit DC2202A EMI Performance in CISPR25 Radiated Emission Test (14V Input from VEMI Turret Pin, IOUT = 4A) 2 dc2202af DEMO MANUAL DC2202A Quick Start Procedure Demonstration circuit 2202A is easy to set up to evaluate the performance of the LT8640. 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 input or output voltage ripple by touching the probe tip directly across the VIN or VOUT and GND terminals. See Figure 5 for the proper scope technique. 1.Place JP1 on BURST position. 2.With power off, connect the input power supply to VEMI and GND. If the EMI/EMC performance is not important, the input EMI filter can be bypassed by connecting the input power supply to VIN and GND. 3.With power off, connect the load from VOUT to GND. 4.Turn on the power at the input. NOTE: Make sure that the input voltage does not exceed 42V. 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 RT should be chose to set the LT8640 switching frequency equal to or below the lowest SYNC frequency. JP1 can also set LT8640 in spread spectrum mode (JP1 on the SPREAD-SPECTRUM position) or pulse-skipping mode (JP1 on the PULSESKIPPING position). Figure 4. Proper Measurement Equipment Setup VOUT GND Figure 5. Measuring Output Ripple dc2202af 3 DEMO MANUAL DC2202A Parts List ITEM QTY REFERENCE PART DESCRIPTION MANUFACTURER/PART NUMBER Required Circuit Components 1 2 C2, C12 CAP., X5R, 1µF, 50V, 10% 0603 TDK, C1608X5R1H105K 2 2 C4, C8 CAP., X7R, 0.1µF, 16V, 10% 0603 MURATA, GRM188R71C104KA01D 3 1 C5 CAP., C0G, 10pF, 25V, ±0.25p 0603 AVX, 06033A100CAT2A 4 1 C6 CAP., X5R, 100µF, 10V, 20% 1210 SAMSUNG, CL32A107MPVNNNE 5 2 C7, C9 CAP., X7R, 1.0µF, 25V, 10% 0603 MURATA, GRM188R71E105KA12D 6 1 C11 CAP., X5R, 10µF, 50V, 10% 1206 TDK, C3216X5R1H106K 7 1 C13 CAP., X5R, 4.7µF, 25V, 10% 0603 MURATA, GRM188R61E475KE11D 8 1 L1 INDUCTOR,1.5µH WÜRTH ELEKTRONIK, 74437346015 8 2 R1, R3 RES., CHIP., 100k, 1/10W, 1% 0603 VISHAY, CRCW0603100KFKEA 9 1 R2 RES., CHIP., 18.2k, 1/10W, 1% 0603 VISHAY, CRCW060318K2FKEA 10 1 R4 RES., CHIP., 1M, 1/10W, 1% 0603 VISHAY, CRCW06031M00FKEA 11 1 R5 RES., CHIP., 243k, 1/10W, 1%, 0603 VISHAY, CRCW0603243KFKEA 12 1 U1 IC, REGULATOR, 20-QFN, UDC LINEAR TECH. CORP., LT8640EUDC#PBF Additional Demo Board Circuit Components 1 1 C1 CAP., ALUM 22µF, 63V SUN ELECT., 63CE22BS 2 2 C3, C10 CAP., X7R, 10µF, 50V, 10% 1210 MURATA, GRM32ER71H106KA12L 3 1 C14 CAP., X7R, 0.1µF, 50V, 10% 0402 TDK, C1005X7R1H104K 4 1 FB1 CHIP BEAD WÜRTH ELEKTRONIK, 74279226101 5 1 L2 RES., CHIP., 0Ω, 3/4W, 2010 VISHAY, CRCW20100000Z0EF 6 0 R6 (OPT) RES., 0603 7 1 R7 RES., CHIP., 0, 1/10W, 0603 VISHAY, CRCW06030000Z0EA Hardware: For Demo Board Only 1 10 E1-E10 TESTPOINT, TURRET, .094" PBF MILL-MAX, 2501-2-00-80-00-00-07-0 2 1 JP1 2×4, 0.079 DOUBLE ROW HEADER WÜRTH ELEKTRONIK, 62000821121 3 1 XJP1 SHUNT, 0.079" CENTER WÜRTH ELEKTRONIK, 60800213421 4 4 MH1-MH4 STAND-OFF, NYLON 0.50" TALL WÜRTH ELEKTRONIK, 702935000 4 dc2202af 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 E5 E6 E2 E1 SYNC BURST VIN R6 OPT R1 100K E10 E7 E9 C14 0.1uF 50V 0402 6 8 5 7 C3 10uF 50V 1210 FB1 74279226101 4 2 3 1 JP1 C10 10uF 50V 1210 5 1. ALL RESISTORS ARE 0603. ALL CAPACITORS ARE 0603. NOTES: UNLESS OTHERWISE SPECIFIED VEMI TR/SS GND PULSE-SKIPPING SPREAD-SPECTRUM SYNC EN/UV GND VIN 5.7V - 42V 2010 L2 0 SUNCON 63CE22BS 4 22uF 63V + C1 VIN C7 1uF 25V C8 0.1uF C11 10uF 50V 1206 R2 18.2K (2MHz) C12 1uF 50V C2 1uF 50V 15 16 2 17 14 13 ** ** 4 CAPACITORS MUST BE PLACED AS CLOSE AS POSSIBLE TO LT8640. SHOULD BE PLACED BETWEEN VIN1 AND GND1. C12 ** C2 SHOULD BE PLACED BETWEEN VIN2 AND GND2. THESE TR/SS INTVCC SYNC EN/UV VIN2 VIN1 RT 3 3 U1 LT8640EUDC 6 7 GND1 10 GND1 11 GND2 GND2 4 GND 18 5 3 FB PG BIAS 20 19 1 8 SW 9 SW 21 SW 22 SW BST R5 243k R7 2 C5 R4 0 100k 10pF 1Meg R3 L1 C4 1.5uH 0.1uF 16V 74437346015 2 C6 100uF 10V 1210 VOUT C9 1uF * 1 E8 E4 E3 C13 4.7uF PG GND VOUT 5V / 5A * SEE DEMO MANUAL 1 A B C D DEMO MANUAL DC2202A Schematic Diagram dc2202af 5 DEMO MANUAL DC2202A 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 dc2202af Linear Technology Corporation LT 0215 • PRINTED IN USA 1630 McCarthy Blvd., Milpitas, CA 95035-7417 (408) 432-1900 ● FAX: (408) 434-0507 ● www.linear.com LINEAR TECHNOLOGY CORPORATION 2015