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TND313/D Rev 3, Sep-11 High-Efficiency 305 W ATX Reference Design Documentation Package © 2011 ON Semiconductor. 1 Disclaimer: ON Semiconductor is providing this reference design documentation package "AS IS" and the recipient assumes all risk associated with the use and/or commercialization of this design package. No licenses to ON Semiconductor's or any third party's Intellectual Property is conveyed by the transfer of this documentation. This reference design documentation package is provided only to assist the customers in evaluation and feasibility assessment of the reference design. The design intent is to demonstrate that efficiencies beyond 80% are achievable cost effectively utilizing ON Semiconductor provided ICs and discrete components in conjunction with other inexpensive components. It is expected that users may make further refinements to meet specific performance goals. 2 Table of Contents 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. Overview ... 6 Specifications ... 7 Architecture Overview ... 8 Performance Results ... 13 Evaluation Guidelines ... 23 Schematics ... 24 Parts List ... 29 Critical Component Information... 35 Resources/Contact Information ... 35 Appendix ... 36 3 List of Tables Table 1: Target Specifications ... 7 Table 2: Load matrix for efficiency measurements ... 13 Table 3: Load matrix for cross regulation measurements ... 15 Table 4: Transient load conditions ... 18 4 List of Figures Figure 1: Reference Design Architecture Block Diagram ... 7 Figure 2: One switch forward topology and associated waveform... 9 Figure 3: Active clamp forward topology and associated waveform ... 11 Figure 4: Efficiency vs percentage load from 20% to full load ... 13 Figure 5: Power factor vs percentage load ... 14 Figure 6: Efficiency vs percentage load from 5% to full load ... 14 Figure 7: 5 V and 5 V SBY outputs cross regulation vs load conditions ... 16 Figure 8: 3.3 V out