±15 Vout from 24 Vin at 80 mA Reference Design PRD1210 FEATURES Small Size Low Cost DESCRIPTION This application note describes a SEPIC-Cuk converter used to create a dual rail output from a single input voltage. A SEPIC-Cuk converter uses a SEPIC and a Cuk converter both tied to the same switch node to create the two separate output rails. In this design, two readily available coupled inductors are used, though a custom three winding transformer would also work. This design utilizes a cascoded FET (Q1) on the switch node. This technique allows the use of an inexpensive low voltage regulator chip (ADP1613) to control a higher voltage converter. In addition it results in very low switching loss, that is offset somewhat by the conduction loss in the cascoded FET. Table 1. Sepcifications Spec Units Vout1 +15V Volts Vout2 -15V Volts Iout1 0.08 Amps Iout2 0.020 Amps Tamb 55 degC Vinmin 24 Volts Vinmax 24 Volts Rev. 0 Reference designs are as supplied “as is” and without warranties of any kind, express, implied, or statutory including, but not limited to, any implied warranty of merchantability or fitness for a particular purpose. No license is granted by implication or otherwise under any patents or other intellectual property by application or use of reference designs. Information furnished by Analog Devices is believed to be accurate and reliable. However, no responsibility is assumed by Analog Devices for its use, nor for any infringements of patents or other rights of third parties that may result from its use. Analog Devices reserves the right to change devices or specifications at any time without notice. Trademarks and registered trademarks are the property of their respective owners. Reference designs are not authorized to be used in life support devices or systems. One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A. Tel: 781.329.4700 www.analog.com Fax: 781.461.3113 ©2009 Analog Devices, Inc. All rights reserved. Reference Design PRD1210 TABLE OF CONTENTS Features ......................................................................................................................................................................1 Description .................................................................................................................................................................1 Revision History .........................................................................................................................................................2 Schematic ...................................................................................................................................................................3 Bill of Materials..........................................................................................................................................................3 Graphs ........................................................................................................................................................................5 TABLE OF FIGURES Figure 1. Schematic ...............................................................................................................................................3 Figure 2. Bode Plot (Full Load both channels) .....................................................................................................5 REVISION HISTORY 2/17/2010—Revision 1: Initial Version Rev. 1 | Page 2 of 6 Reference Design PRD1210 SCHEMATIC Figure 1. Schematic BILL OF MATERIALS Table 2. Bill of Materials U1 ADI Integrated Switching Regulator L1 Coilcraft 82uH, 3410mΩ, 0.3Apk LPD4012-823 4mm x 4mm x 1.2mm 1 16.1 1.2 0.600 L2 Coilcraft 82uH, 3410mΩ, 0.3Apk LPD4012-823 4mm x 4mm x 1.2mm 1 16.1 1.2 0.600 Q1 Vishay 128 mΩ, 2.9 Vth,60 V Si3458BDV SOT23-6 1 9.3 1.1 0.700 D1 ON Semi 2 A, 100 V MBRS1100T3G SMB 1 21.3 2.4 0.100 ADP1613ARMZ MSOP-8 1 14.7 1.1 0.700 Rev. 1 | Page 3 of 6 Reference Design PRD1210 U1 ADI Integrated Switching Regulator D2 ON Semi 2 A, 100 V MBRS1100T3G SMB 1 21.3 2.4 0.100 Cout1 Taiyo Yuden 1uF, 25V, 11mΩ TMK107 BJ105MAT 0603 1 1.3 0.8 0.009 Cout2 Taiyo Yuden 1uF, 25V, 11mΩ TMK107 BJ105MAT 0603 1 1.3 0.8 0.009 Cin1 Murata 0.1uF, 100V, 40mΩ GRM188R72A104 0603 1 1.3 0.8 0.031 C1 Murata 0.1uF, 100V, 40mΩ GRM188R72A104 0603 1 1.3 0.8 0.031 C2 Murata 0.1uF, 100V, 40mΩ GRM188R72A104 0603 1 1.3 0.8 0.031 Rc1 Vishay 5% tolerance 2.61 kOhms 0805 1 2.5 0.5 0.005 Cc1 Vishay 10% tolerance 27 nF 0805 1 2.5 0.5 0.010 Cc2 Vishay 10% tolerance 150 pF 0805 1 2.5 0.5 0.010 Rf1B Vishay 47.5 kOhms 1% tolerance 0805 1 2.5 0.5 0.005 Rf2 Vishay 4.22 kOhms 1% tolerance 0805 1 2.5 0.5 0.005 Cv5 Murata 1uF,10V,X5R GRM188R61A105K 0603 1 1.3 0.6 0.010 Css Vishay 10% tolerance 10 nF 0805 1 2.5 0.5 0.010 Z2 Diodes Inc. 5.1V, 500 mW Zener DDZ9690 SOD-123 1 2.5 1.1 0.026 Rb1 Vishay 95.3 kOhms 5% tolerance 0805 1 2.5 0.5 0.005 Q2 On Semi 40V,NPN,300mW MMBT3904LT1G SOT-23 1 7.4 1.11 0.020 Totals 21 134.0 max=2.4 ADP1613ARMZ MSOP-8 1 14.7 1.1 0.700 Rev. 1 | Page 4 of 6 3.02 Reference Design PRD1210 GRAPHS Figure 2. Bode Plot (Full Load both channels) Rev. 1 | Page 5 of 6 Reference Design PRD1210 NOTES ©2009 Analog Devices, Inc. All rights reserved. Trademarks and registered trademarks are the property of their respective owners. Error! Unknown document property name. Rev. 1 | Page 6 of 6