Description Demonstration circuit 20 is a monolithic step-down converter featuring LT 86. The demo board is designed for V output from a 6.V to 00V input at 400kHz switching frequency. The wide input range makes it suitable for regulating power from a wide variety of sources, including automotive, industrial systems and telecom supplies. The LT86 is a compact, high efficiency synchronous monolithic step-down switching regulator. The power switch, compensation and other necessary circuits are inside of the LT86 to minimize external components and simplify design. The LT86 switching frequency can be programmed either via oscillator resistor or external clock over a 00kHz to MHz range. The SYNC pin on the demo board is grounded (JP at Burst Mode position) by default for low ripple Burst Mode operation. To synchronize to an external clock, move JP to SYNC and apply the external clock to the SYNC turret. If the pulse-skipping operation is required, move JP to fixed frequency position. Figure shows the efficiency of the circuit at 2V input at the Burst Mode selection. The demo board has an EMI filter installed. The EMI performance of the board (with EMI filter) is shown in Figure 2. The red line in Figure 2 is CISPR2 Class peak limit. The figure shows that the circuit passes the test with a wide margin. To achieve EMI/EMC performance as shown Performance Summary DEMO MNUL DC20 LT86 00V, Synchronous Micropower Step-Down Regulator in Figure 2, the input EMI filter is required and the input voltage should be applied at V EMI turret pin, not V IN. The LT86 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 20. The LT86 is assembled in a 20-lead TSSOP packages. Proper board layout is essential for maximum thermal and electrical performance. See the data sheet sections for details. Design files for this circuit board are available at http://www.linear.com/demo/dc20 L, LT, LTC, LTM, Linear Technology, Burst Mode and the Linear logo are registered trademarks of Linear Technology Corporation. ll other trademarks are the property of their respective owners. Specifications are at T = 2 C 0. 0.2 0. 0.4 0. 0.6 0.7 0.8 0.9 LOD CURRENT () Figure. LT86 Efficiency vs Load Current SYMBOL PRMETER CONDITIONS MIN TYP MX UNITS V IN Input Supply Range 6. 00 V V OUT Output Voltage 4.88.04.2 V f SW Switching Frequency R T = 2.kΩ 70 400 40 khz I OUT Max Output Current V IN = 2V E FE Efficiency at DC V IN = 2V, I OUT = 82.6 % V IN = 2V, I OUT = 0.4 89. % EFFICIENCY (%) 9 90 8 80 7 70 6 60 0 0 f SW = 400kHz V IN = 2V V OUT = V DC20a F0
Quick Start Procedure Demonstration circuit 20 is easy to set up to evaluate the performance of the LT86. Refer to Figure 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 V IN or V OUT and terminals. See Figure 4 for the proper scope technique.. Place JP on position. 2. With power off, connect the input power supply to V EMI and. If the EMI/EMC performance is not important, the input EMI filter can be bypassed by connecting the input power supply to V IN and.. With power off, connect loads from V OUT to. 4. Turn on the power at the input. Make sure that the input voltage does not exceed 00V.. Check for the proper output voltages (V OUT = V). 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. n external clock can be added to the SYNC terminal when SYNC function is used (JP on the SYNC position). Please ensure that the chosen RT sets the LT86 switching frequency to 0% below the lowest SYNC frequency. See the data sheet Synchronization section for details. mplitude (dbuv/m) 0 4 40 0 2 20 0 0 - Detector: Peak Polarity: Vertical 0 00 200 00 400 00 600 700 800 900 000 Frequency (MHz) Data Class Peak mplitude (dbuv/m) Detector: Peak 0 Polarity: Horizontal 4 40 0 2 20 0 0-0 00 200 00 400 00 600 700 800 900 000 Frequency (MHz) Data Class Peak Figure 2. LT86 Demo Circuit DC20 EMI Performance in CISPR2 Radiated Emission Test (4V Input from V EMI Turret Pin, I OUT = ) 2
Quick Start Procedure I IN POWER SUPPLY V V IN V V OUT I OUT LOD Figure. Proper Measurement Equipment Setup V OUT Figure 4. Measurement Input or Output Ripple
Parts List ITEM QTY REFERENCE PRT DESCRIPTION MNUFCTURER/PRT NUMBER Required Circuit Components C CP, 0.µF, X7R, 0V, 0% 0402 TDK, C00X7R04K 2 C CP, 2.2µF, XR, 0V, 0% 0402 TDK, C00XR22K00BC C6 CP, 4.7pF, C0G, 0V, 0.2pF 060 MURT, GRM88CH4R7C0D 4 C7 CP, 47µF, X7R, 0V, 20% 20 MURT, GRM2ER7476KEL C8 CP, 0.µF, X7R, 0V, 0% 060 VX, 060ZC04KT2 6 C4 CP, µf, X7R, 0V, 0% 060 SMSUNG, CL0B0KP8NNNC 7 L INDUCTOR, 22µH IHLP22 VISHY, IHLP22CZER220M 8 L2 INDUCTOR, 2.2µH COILCRFT, XFL4020-222MEB 9 R RES,.k, /0W, % 060 VISHY, CRCW060KFKE 0 2 R2, R4 RES, M, /0W, % 060 VISHY, CRCW060M00FKE R RES, 2.k, /0W, % 060 VISHY, CRCW0602KFKE 2 R RES, CHIP, 9k, /0W, % 060 VISHY, CRCW0609KFKE U IC, BUCK REG FE-20(6) CB LINER TECHNOLOGY, LT86EFE#PBF dditional Demo Board Circuit Components C2 CP, LUM, 0µF, 00V SUN ELECTRONIC, 00CE0BS 2 0 C (OPT) CP, 060 0 D (OPT) SCHOTTKY BRRIER REC, POWER-DI-2 Hardware: For Demo Board Only 0 E TO E0 TEST POINT, TURRET, 0.094" MTG.HOLE MILL-MX, 20-2-00-80-00-00-07-0 2 JP 4 PIN 0.079 SINGLE ROW HEDER SULLIN, NRPN04PEN-RC XJP SHUNT, 0.079" CENTER SMTEC, 2SN-BK-G 4 0 R6 (OPT) RES, 060 4 MH TO MH4 STND-OFF, NYLON 0.0" KEYSTONE, 88 (SNP ON) 4
Schematic Diagram B C D E C 0.uF 00V U LT86EFE VIN VIN R VIN SW 6.V - 00V 20 E2 C2 C.k C 8 EN/UV BST 0.uF D 0uF 2.2uF 0402 DFLS00 4 4 E 00V 00CE0BS 00V 0V R4 INTVCC 6 L OPT 20 PG M 22uH NC C 6 NC 2.2uF 0V IHLP22CZER220M 7 SYNC/MODE IND 4 0402 EN/UV 8 RT NC E4 9 2 VOUT NC VOUT 0 C4 TR/SS FB R C7 V / E R6 R2 C6 47uF OPT M uf 4.7pF 2.K % 0V 0V (400kHz) 20 C8 2 0.uF E6 R 9k % E PG TR/SS E0 FIXED FREQ BURST MODE SYNC 2 4 SYNC E7 JP L2 2 VIN 2 2.2uH VEMI E8 XFL4020-222ME C9 2.2uF 00V 20 C0 2.2uF 00V 20 E9 LINER TECHNOLOGY HS MDE BEST EFFORT TO DESIGN NOTE: UNLESS OTHERWISE SPECIFIED CIRCUIT THT MEETS CUSTOMER-SUPPLIED SPECIFICTIONS; TECHNOLOGY Fax: (408)44-007 HOWEVER, IT REMINS THE CUSTOMER'S RESPONSIBILITY TO VERIFY PROPER ND RELIBLE OPERTION IN THE CTUL LTC Confidential-For Customer Use Only. LL RESISTORS RE 060. LL CPCITORS RE 060. PPLICTION. COMPONENT SUBSTITUTION ND PRINTED TITLE: SCHEMTIC CIRCUIT BORD LYOUT MY SIGNIFICNTLY FFECT CIRCUIT PERFORMNCE OR RELIBILITY. CONTCT LINER TECHNOLOGY PPLICTIONS ENGINEERING FOR SSISTNCE. 00V SYNCHRONOUS B CUSTOMER NOTICE THIS CIRCUIT IS PROPRIETRY TO LINER TECHNOLOGY ND SUPPLIED FOR USE WITH LINER TECHNOLOGY PRTS. C SIZE N/ DTE: IC NO. REV. D 60 McCarthy Blvd. Milpitas, C 90 Phone: (408)42-900 MICROPOWER BUCK REGULTOR LT86EFE DEMO CIRCUIT 20 Tuesday, July 07, 20 SHEET OF E www.linear.com 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.
DEMONSTRTION BORD IMPORTNT NOTICE Linear Technology Corporation (LTC) provides the enclosed product(s) under the following S IS conditions: This demonstration board (DEMO BORD) kit being sold or provided by Linear Technology is intended for use for ENGINEERING DEVELOPMENT OR EVLUTION PURPOSES ONLY and is not provided by LTC for commercial use. s such, the DEMO BORD 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. s 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 BORD manual the kit may be returned within 0 days from the date of delivery for a full refund. THE FOREGOING WRRNTY IS THE EXCLUSIVE WRRNTY MDE BY THE SELLER TO BUYER ND IS IN LIEU OF LL OTHER WRRNTIES, EXPRESSED, IMPLIED, OR STTUTORY, INCLUDING NY WRRNTY OF MERCHNTBILITY OR FITNESS FOR NY PRTICULR PURPOSE. EXCEPT TO THE EXTENT OF THIS INDEMNITY, NEITHER PRTY SHLL BE LIBLE TO THE OTHER FOR NY INDIRECT, SPECIL, INCIDENTL, OR CONSEQUENTIL DMGES. 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. lso 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 BORD 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 ddress: Linear Technology 60 McCarthy Blvd. Milpitas, C 90 Copyright 2004, Linear Technology Corporation 6 LT 09 PRINTED IN US Linear Technology Corporation 60 McCarthy Blvd., Milpitas, C 90-747 (408) 42-900 FX: (408) 44-007 www.linear.com LINER TECHNOLOGY CORPORTION 20