LM5072EVAL National Semiconductor, LM5072EVAL Datasheet - Page 4

• Manufacturer Part Number: LM5072EVAL
• Description: BOARD EVALUATION LM5072
• Manufacturer: National Semiconductor
• Series: PowerWise®r

Specifications of LM5072EVAL

• Main Purpose: Special Purpose DC/DC, Power Over Ethernet
• Outputs And Type: 1, Isolated
• Power - Output: 9.9W
• Voltage - Output: 3.3V
• Current - Output: 3A
• Voltage - Input: 38 ~ 60V
• Regulator Topology: Flyback
• Frequency - Switching: 250kHz
• Board Type: Fully Populated
• Utilized Ic / Part: LM5072
• Lead Free Status / RoHS Status: Not applicable / Not applicable

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Power Up
(+3.3V) and J5 (3.3V RTN), will allow direct measurement of
the 3.3V output line. If the 3.3V output voltage is not ob-
served within a few seconds, turn the power supply off and
review connections.
A final check of efficiency is the best way to confirm that the
unit is operating properly. Efficiency significantly lower than
80% at full load indicates a problem.
After proper PoE operation is verified, the user may apply
auxiliary power to the FAUX or RAUX inputs. It is recom-
mended that the application of the auxiliary power follow the
same precautions as those taken when applying PoE. If no
output voltage is observed, it is likely that the auxiliary power
feed polarity is reversed. After successful operation is ob-
served in both FAUX and RAUX modes, full power testing
can begin.
PD Interface Operating Modes
When connecting into the PoE system, the evaluation
board’s Powered Device interface will go through the follow-
ing operating modes in sequence: PD signature detection,
power level classification (optional), and application of full
Class
0
1
2
3
4
(Continued)
Reserved
0.44W
0.44W
3.84W
6.49W
P
MIN
Reserved
12.95W
12.95W
3.84W
6.49W
P
MAX
I
CLASS
4
17mA
26mA
36mA
0mA
9mA
power. Refer to the LM5072 datasheet and IEEE 802.3af for
detailed information about these operating modes.
Signature Detection
The 25 kΩ PD signature resistor is integrated into the
LM5072 IC. The PD signature capacitor is implemented with
a 100 nF capacitor at C27 or C29, depending on the auxiliary
input configuration.
It should be noted that when either FAUX or RAUX power is
applied first, it will not allow the Power Sourcing Equipment
(PSE) to identify the PD as a valid device because the
auxiliary voltage will cause the current steering diode
bridges to be reverse biased during detection mode. This
prevents the PSE from applying power, so the evaluation
board will only draw current from the auxiliary source.
Classification
PD classification is implemented with R22. The evaluation
board is set to the default Class 0 by leaving the RCLASS
pin open (R22 position not populated). To activate a specific
class instead of Class 0, install R22 according to the follow-
ing table.
(MIN)
I
CLASS
12mA
20mA
30mA
44mA
4mA
(MAX)
R22 Selection
71.5Ω
46.4Ω
31.6Ω
Open
130Ω