National Semiconductor POEPHYTEREV-E, User Manual

Page 1: ...rsions There are two versions of PCBs being built which can be identified by the PCB serial number printed along the left edge of the top side the circuit board One version is labelled 551012916 001 Rev A the other 551013040 001 Rev A The first version cannot modify the 3 3V output to higher voltages because it is directly connected to the PHY through inner lay ers It is modified on the second ver...

Page 2: ...oard setting for the PHY Address is 01h The board may be set to PHY Address 03h by adding jumper J3 Table of Jumpers Jumper Name Function J1 MII Male Connector MII interface J2 MII Header Alternative connection for MII signals J3 PHYAD1 PHY Address strap pin J4 MDIX_EN Enable Disable MDIX mode Default is Auto MDIX Enable J5 LED_CFG Set LED configuration See datasheet J6 Not populated J7 MII 3V3 op...

Page 3: ... such power levels may violate safety regulations and may cause damage A Note about PoE Input Potentials PoE applications are typically 48V systems in which the no tations GND and 48V normally refer to the high and low input potentials respectively However for easy readability the LM5072 datasheet was written in the positive voltage con vention with positive input potentials referenced to the VEE ...

Page 4: ...20205201 FIGURE 1 Evaluation Board Schematic Part 1 The Ethernet Circuit www national com 4 AN 1521 ...

Page 5: ...20205212 FIGURE 2 Evaluation Board Schematic Part 2 RJ45 connectors and Ethernet Magentics 5 www national com AN 1521 ...

Page 6: ...20205213 FIGURE 3 Evaluation Board Schematic Part 3 the PoE Circuit www national com 6 AN 1521 ...

Page 7: ...to the center pin of P1 When using TP3 and TP4 for the quick AUX input connection to a bench power supply be aware that TP3 is the high potential pin The diode DE1 provides the re verse protection of the AUX input Please note that TP4 and TP8 are two different return pins for the PoE and AUX inputs respectively They are not connect ed to the same circuit node and they should not be inter changed F...

Page 8: ...testing can begin PD Interface Operating Modes When connecting into the PoE system the evaluation board will go through the following operating modes in sequence PD signature detection power level classification optional and application of full power See the LM5072 datasheet for details Signature Detection The 25 kΩ PD signature resistor is integrated into the LM5072 IC The PD signature capacitor ...

Page 9: ...former winding pro duces an output about 2V higher than the startup regulator output thus shutting off the startup regulator and reducing the power dissipation inside the IC Given the low current limit value 15 mA nominal of the high voltage startup regulator the VCC line is not meant to source external loads greater than 3 mA in total The external load of the VCC line is the PoE Power LED indicat...

Page 10: ...ntain the output voltage This initiates cycle by cycle over current limiting which turns off the main switch when the current sense CS pin exceeds the current limit threshold 2 The current in the internal hot swap MOSFET increases until it is current limited around 800 mA Some overshoot in the current will be observed as it takes time for the current limit amplifier to react and change the operati...

Page 11: ... pin referenced to the VEE pin 0 5V div Trace 2 The PoE input current 0 5A div FIGURE 9 Retry Mode under 38V PoE Input and Output Over Current Condition STEP RESPONSE Figure 10 shows the step load response at Vin equal to 48V The load current changes in step between 1A and 7A 20205208 Horizontal Resolution 0 5 ms div Trace 1 Load current step changes between 1A and 7A 2A div Trace 2 The 3 3V outpu...

Page 12: ...showing the peak value of the harmonics Hor izontal 500 kHz div Vertical 5 mV div FIGURE 13 Output Ripple Voltage under Full Load A Note on the Use of Common Mode Choke A location is reserved on the evaluation board for an optional input common mode filter For some special applications that have very strict EMI requirements the common mode filter consisting of the choke U6 and two Y capacitors CE1...

Page 13: ...3V CE19 C2012X5R1C105K CAPACITOR CER CC0805 TDK 1 0 µF 16V CE20 C2012X7R1E474K CAPACITOR CER CC0805 TDK 0 4 µF 25V CE21 C0805C473K5RAC CAPACITOR CER CC0805 KEMET 0 047 µF 50V CE22 NU CE23 C0805C102K5RAC CAPACITOR CER CC0805 KEMET 1000 pF 50V CE25 C0805C104K5RAC CAPACITOR CER CC0805 KEMET 0 1 µF 50V CE26 C0805C473K5RAC CAPACITOR CER CC0805 KEMET 0 047 µF 50V CE27 NU CE28 C4532X7R3D222K CAPACITOR CE...

Page 14: ...RESISTOR 20 Ohm RE4 NU RE5 CRCW08053321F RESISTOR 3 32 kΩ RE6 CRCW080524R9J RESISTOR 24 9 Ohm RE7 CRCW080510R0F RESISTOR 10 Ohm RE8 NU RE9 CRCW08051000F RESISTOR 100 Ohm RE10 NU RE11 NU RE12 CRCW08052432F RESISTOR 24 3 kΩ RE13 CRCW08054991F RESISTOR 4 99 kΩ RE14 CRCW12060R47F RESISTOR 0 47 Ohm RE15 CRCW12060R47F RESISTOR 0 47 Ohm RE16 NU RE17 CRCW08055900F RESISTOR 1 kΩ RE18 CRCW08051472F RESISTOR...

Page 15: ...OR CER CC0603 KEMET 0 1 µF 50V C15 CAPACITOR CER CC0603 KEMET 0 1 µF 50V C16 CAPACITOR CER CC0603 KEMET 0 1 µF 50V C17 CAPACITOR TAN CC7343 10 µF 35V C18 CAPACITOR CER CC0603 KEMET 0 1 µF 50V C20 CAPACITOR TAN CC7343 10 µF 35V C21 CAPACITOR CER CC0603 KEMET 0 1 µF 50V C22 CAPACITOR CER CC0603 KEMET 0 1 µF 50V C23 CAPACITOR CER CC0603 KEMET 0 1 µF 50V C49 CAPACITOR CER CC0603 KEMET E Board ONLY 8 p...

Page 16: ... Ohm R18 CRCW060333R0J RESISTOR 33 Ohm R19 CRCW060333R0J RESISTOR 33 Ohm R20 CRCW060333R0J RESISTOR 33 Ohm R21 CRCW060333R0J RESISTOR 33 Ohm R22 CRCW060333R0J RESISTOR 33 Ohm R23 CRCW060333R0J RESISTOR 33 Ohm R24 CRCW060333R0J RESISTOR 33 Ohm R25 CRCW060333R0J RESISTOR 33 Ohm R26 CRCW06032200F RESISTOR 220 Ohm R28 CRCW08051501F RESISTOR 1 5 kΩ R29 CRCW06032201F RESISTOR 2 2 kΩ R30 CRCW060324871F R...

Page 17: ...Ohm R56 CRCW12060R0J RESISTOR 0 Ohm R57 CRCW12060R0J RESISTOR 0 Ohm U1 DP83848 IVV PHY TRANSCEIVER NATIONAL U4 ETH1 230LD TRANSFORMER ETHERNET COILCRAFT E BOARD ONLY U8 NU U9 NU U10 NU UE13 0838 1X1T W6 CONNECTOR INTEGRATED WITH ETHERNET TRANSFORMER BEL STEWARD I BOARD ONLY Y1 FOXSLF 250F 20 CRYSTAL HC49 US 25 MHz Note NU stands for Not Used namely not populated 17 www national com AN 1521 ...

Page 18: ...PRODUCTS AND APPLICATIONS USING NATIONAL COMPONENTS PRIOR TO USING OR DISTRIBUTING ANY PRODUCTS THAT INCLUDE NATIONAL COMPONENTS BUYERS SHOULD PROVIDE ADEQUATE DESIGN TESTING AND OPERATING SAFEGUARDS EXCEPT AS PROVIDED IN NATIONAL S TERMS AND CONDITIONS OF SALE FOR SUCH PRODUCTS NATIONAL ASSUMES NO LIABILITY WHATSOEVER AND NATIONAL DISCLAIMS ANY EXPRESS OR IMPLIED WARRANTY RELATING TO THE SALE AND...