UM1063 STMICROELECTRONICS | Alldatasheet
Document overview
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- PDF pages: 32
Technical content
Datasheet sections
- 1 Electrical specifications
- 2 Demonstration kit schematic
- 3 Board layout
- 4 I/O connectors and test points
- 5 Bill of material
- 6 Power-up sequence
- 7 Test results
- 7.2 Efficiency measurements with 5 V output
- 7.3 Waveforms
- 7.3.1 Startup sequence from PoE/PoE+ injectors
- 7.3.2 Transition from PoE to auxiliary and auxiliary to PoE
- 7.3.3 Primary side MOSFET
- 7.3.4 Secondary side MOSFET
- 7.3.5 Line transient
- 7.3.6 Load transient
- 7.3.7 Output ripple
- 8 Revision history
1 Electrical specifications
Table 1. Specifications for 3.3 V output
3.3 V efficiency DC-DC only Vin=48 V, Iout=Imax 90 %
3.3 V overall efficiency Vin=48 V, Iout=Imax 87 %
Table 2. Specifications for 5 V output
5 V efficiency DC-DC only Vin=48 V, Iout=Imax 92 %
5 V overall efficiency Vin=48 V, Iout=Imax 89 %
2 Demonstration kit schematic
Figure 2. Demonstration kit schematic: detail of the PoE+ input section including data
Figure 3. Demonstration kit schematic: detail of the PoE+ section based on flyback topology with
2 K2 K
3 Board layout
Board size: 10 x 16 cm. Layer copper thickness: 70 micron. Figure 4. Assembly view: top layer Figure 5. Assembly view: bottom layer
4 I/O connectors and test points
commands (Table 4), as well as the available test points (Table 5). Table 3. Connectors source without priority in respect to PoE. source with priority in respect to PoE. Table 4. LEDs signal is de-asserted and the L1_OK LED is turned off. D26 GREEN LED ON when output voltage is present. Table 5. Test points
Table 5. Test points (continued)
5 Bill of material
rectification using a gatedriver transformer. With minimal BOM changes it is possible to switch from 3.3 V to 5 V output voltage. Table 6. EVALPM8803-FWD BOM
88 C1,C2,C3,C4,C11C36,
66 C10,C39,C41,C48C53,
66 C27,C33,C35,C37C67,
88 D4,D7,D8,D9,D12D13,
66 D28,D34,D36,D37D39,
Table 6. EVALPM8803-FWD BOM (continued)
4 A 805 TDK
66 R60,R64,R68,
77 TP3,TP8,TP11,
1 NM T5 Power transformer JA4173-AL Coilcraft
11 T 8 Gate driver
6 Power-up sequence
It is recommended to apply power at PoE input first, slowly increasing the voltage to verify the absence of abnormal input current levels. From about 2 V to about 12 V input, the demonstration kit performs the detection signature. At 10 V input the current drawn is about 400 µA. In the range of 14 V to 23 V, the demonstration kit performs a class-4 classification, and the current drawn is about 40 mA. After those two steps are verified, the voltage can be increased to 48 V typical. The PoE converter starts operations at about 36 V input. Three green LEDs indicate proper operation of the PoE and DC-DC section of the PM8803 demonstration kit:
- D44 is the T2P LED and is ON when the PM8803 has successfully recognized a type 2 PSE or a 802.3at compliant injector; using a bench power supply to power up the PM8803 demonstration board, this LED is OFF.
- D26 indicates the presence of the output voltage.
- D20 is the AUX LED and indicates the presence of an auxiliary voltage applied to the converter; proper selection of the auxiliary voltage is done with jumper JM1 and JM2: put a short between pin 1 and 2 when SA auxiliary source on J1 connector is used; put the short between pin 2 and 3 when SP auxiliary source on J2 connector is used. Note: Set the R73 trimmer at a value around 10 k Ω Adjust this value for best converter performances in terms of efficiency over its actual load range. Note: In the case of SA external auxiliary source tests, it is strongly recommended to change the position of the 100 nF, 100 V from C18, at the input filter, where it is soldered to C60, across the internal hot-swap MOSFET. This change of position, that has no impact on the standard compliance, permits an optimal behavior of the PM8803 device during the change of ground reference consequent to the power jack insertion/removal.
7 Test results
Figure 10. Efficiency measurements at 48 V input Figure 11. DC-DC only efficiency measurements
Figure 12. Overall efficiency measurements
7.2 Efficiency measurements with 5 V output
Figure 13. Efficiency measurements at 48 V input
7.3 Waveforms
are also applicable for the 3.3 V output version.
7.3.1 Startup sequence from PoE/PoE+ injectors
Figure 16. Startup from an IEEE 802.3af injector with 2 A load Note the inrush current limited at about 140 mA and the T2P signal not asserted. Figure 17. Startup from an IEEE 802.3at injector with 4 A load
signal now asserted (T2P is valid low).
7.3.2 Transition from PoE to auxiliary and auxiliary to PoE
seen from the output voltage (blue line). Figure 18. Switching between PoE and auxiliary source
7.3.3 Primary side MOSFET
Figure 19. Primary side power MOSFET waveforms at 0 A load Figure 20. Primary side power MOSFET waveforms at 4 A load
Figure 21. Details of primary side power MOSFET waveforms at 4 A load
7.3.4 Secondary side MOSFET
Figure 22. Secondary side power MOSFET waveforms at 0 A load
Figure 23. Secondary side power MOSFET waveforms at 4 A load
7.3.5 Line transient
converter continues to work and the output voltage (blue trace) remains in regulation. Figure 24. Effect of a 12 V line transient on the converter at 4 A load Figure 25. Effect of a 12 V line transient on the converter at 0 A load
7.3.6 Load transient
Figure 26. Response of the converter to a 2 A - 4 A load transient Figure 27. Response of the converter to a 0 A - 4 A load transient
7.3.7 Output ripple
Figure 28. Output ripple measurement at 4 A Figure 29. Output ripple measurement at 4 A with infinite persistence
8 Revision history
Table 7. Document revision history 23-Mar-2011 1 Initial release. 18-Feb-2013 2 Document title has been changed.