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february 2013 docid018573 rev 2 1/32 UM1063 user manual evalpm8803-fly: ieee802.3at compliant demonstration kit with synchronous flyback converter by antonio rotta introduction the pm8803 is a highly integrated device embedding an ieee802.3at-2009 compliant powered device (pd) interface together with a pwm controller and support for auxiliary sources. figure 1 is an image of the evalpm8803-fly poe+ demonstration board. the same pcb can be populated with different components to support various configurations and topologies (synchronous flyback with or without active clamp, flyback with diode rectification). this document focuses on a reference design for poe+ based on flyback topology with synchronous rectification, with the pm8803 as the main controller. the schematics and board layout of the poe+ converter are given in section 2 and 3 while the related bill of material is detailed in section 5 . in section 7 efficiency measurements together with main waveforms of the poe interface and flyback converter are shown. figure 1. evalpm8803-fly demonstration kit www.st.com
contents UM1063 2/32 docid018573 rev 2 contents 1 electrical specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 2 demonstration kit schematic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 3 board layout . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 4 i/o connectors and test points . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 5 bill of material . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 6 power-up sequence . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 7 test results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 7.1 efficiency measurement with 3.3 v output . . . . . . . . . . . . . . . . . . . . . . . . 20 7.2 efficiency measurements with 5 v output . . . . . . . . . . . . . . . . . . . . . . . . 21 7.3 waveforms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 7.3.1 startup sequence from poe/poe+ injectors . . . . . . . . . . . . . . . . . . . . . . 23 7.3.2 transition from poe to auxiliary and auxiliary to poe . . . . . . . . . . . . . . 24 7.3.3 primary side mosfet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 7.3.4 secondary side mosfet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26 7.3.5 line transient . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28 7.3.6 load transient . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29 7.3.7 output ripple . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30 8 revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31 docid018573 rev 2 3/32 UM1063 list of tables list of tables table 1. specifications for 3.3 v output . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 table 2. specifications for 5 v output . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 table 3. connectors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 table 4. leds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 table 5. test points . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 table 6. evalpm8803-fwd bom . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 3 table 7. document revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31 list of figures UM1063 4/32 docid018573 rev 2 list of figures figure 1. evalpm8803-fly demonstration kit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 figure 2. demonstration kit schematic: detail of the poe+ input section including data transformer, diode bridges, protection, and optional cm choke . . . . . . . . . . 6 figure 3. demonstration kit schematic: detail of the poe+ section based on flyback topology with synchronous rectification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 figure 4. assembly view: top layer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 figure 5. assembly view: bottom layer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 figure 6. top layer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 figure 7. inner layer 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 figure 8. inner layer 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 figure 9. bottom layer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 figure 10. efficiency measurements at 48 v input . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 0 figure 11. dc-dc only efficiency measurements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 figure 12. overall efficiency measurements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 figure 13. efficiency measurements at 48 v input . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 1 figure 14. dc-dc only efficiency measurements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 figure 15. overall efficiency measurements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 figure 16. startup from an ieee 802.3af injector with 2 a load. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 figure 17. startup from an ieee 802.3at injector with 4 a load. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 figure 18. switching between poe and auxiliary source . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24 figure 19. primary side power mosfet waveforms at 0 a load. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 figure 20. primary side power mosfet waveforms at 4 a load. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 figure 21. details of primary side power mosfet waveforms at 4 a load . . . . . . . . . . . . . . . . . . . . . 26 figure 22. secondary side power mosfet waveforms at 0 a load . . . . . . . . . . . . . . . . . . . . . . . . . . 26 figure 23. secondary side power mosfet waveforms at 4 a load . . . . . . . . . . . . . . . . . . . . . . . . . . 27 figure 24. effect of a 12 v line transient on the converter at 4 a load. . . . . . . . . . . . . . . . . . . . . . . . . 28 figure 25. effect of a 12 v line transient on the converter at 0 a load. . . . . . . . . . . . . . . . . . . . . . . . . 28 figure 26. response of the converter to a 2 a - 4 a load transient . . . . . . . . . . . . . . . . . . . . . . . . . . . 29 figure 27. response of the converter to a 0 a - 4 a load transient . . . . . . . . . . . . . . . . . . . . . . . . . . . 29 figure 28. output ripple measurement at 4 a . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30 figure 29. output ripple measurement at 4 a with infinite persistence . . . . . . . . . . . . . . . . . . . . . . . . 30 docid018573 rev 2 5/32 UM1063 electrical specifications 1 electrical specifications table 1. specifications for 3.3 v output parameter description min. typ. max. unit input voltage range applied at j3 connector 0 57 v operative input voltage 42 57 v uvlo vin rising edge 36 v vin falling edge 30 v auxiliary input voltage range 35 60 v output voltage (vout) vin= 42 v to 57 v, iout 0 to imax 3.25 3.35 3.45 v output current (iout) vin= 42 v to 57 v 0 6 a peak-to-peak output ripple 48 vin, iout=imax 20 30 mvpp inrush current limit 140 ma dc current limit 640 ma 3.3 v efficiency dc-dc only vin=48 v, iout=imax 90 % 3.3 v overall efficiency vin=48 v, iout=imax 87 % switching frequency 200 khz table 2. specifications for 5 v output parameter description min. typ. max. unit input voltage range applied at j3 connector 0 57 v operative input voltage 42 57 v uvlo vin rising edge 36 v vin falling edge 30 v auxiliary input voltage range 35 60 v output voltage (vout) vin= 42 v to 57 v, iout 0 to imax 4.95 5.1 5.25 v output current (iout) vin= 42 v to 57 v 0 4 a peak-to-peak output ripple 48vin, iout=imax 20 30 mvpp inrush current limit 140 ma dc current limit 640 ma 5 v efficiency dc-dc only vin=48 v, iout=imax 92 % 5 v overall efficiency vin=48 v, iout=imax 89 % switching frequency 200 khz demonstration kit schematic UM1063 6/32 docid018573 rev 2 2 demonstration kit schematic figure 2. demonstration kit schematic: detail of the poe+ input section including data transformer, diode bridges, protection, and optional cm choke ! - v 3 3 6 3 3 6 3 3 6 3 3 6 3 3 6 3 3 6 3 3 6 3 3 6 3 3 6 3 3 6 3 3 6 3 3 6 3 3 6 3 3 6 3 3 6 3 3 6 3 3 6 3 3 6 3 3 6 3 3 6 3 3 6 & % / 0 & % / 0 & % / 0 0 / % & 6 3 3 6 / 5 4 3 0 # h a s s i s # h a s s i s # h a s s i s # h a s s i s # h a s s i s # h a s s i s 2 4 . 2 4 . ! 5 8 ! u x i l i a r y i n p u t f r o n t a l o r ! 5 8 / p t i o n 3 t a n d a r d $ i o d e " r i d g e . o t - o u n t e d / p t i o n 3 t a n d a r d $ i o d e " r i d g e . o t - o u n t e d / p t i o n ! c t i v e " r i d g e . o t - o u n t e d / p t i o n ! c t i v e " r i d g e . o t - o u 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