Maker : National Semiconductor
Part No. : 5071MT

  Datasheet PDF : 5071MT.pdf
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Product Information

November 2005 www.DataSheet4U.com LM5071 Power Over Ethernet PD Controller with Auxiliary Power Interface LM5071 Power Over Ethernet PD Controller with Auxiliary Power Interface General Description The LM5071 power interface port and pulse width modulation (PWM) controller provides a complete integrated solution for Powered Devices (PD) that connect into Power over Ethernet (PoE) systems. The LM5071 is specifically designed for the PD that must accept power from auxiliary sources such as ac adapters. The auxiliary power interface of the LM5071 activates the PWM controller when the ac adapter is connected to power the PD when PoE network power is unavailable. The LM5071 integrates an 80V, 400mA line connection switch and associated control for a fully IEEE 802.3af compliant interface with a full featured current mode pulse width modulator dc-dc converter. All power sequencing requirements between the controller interface and switch mode power supply (SMPS) are integrated into the IC. n Detection Resistor Disconnect Function n Programmable Classification Current n Programmable Under-voltage Lockout with Programmable Hysteresis n Thermal Shutdown Protection n Auxiliary Power Enable Pin n Current Mode Pulse Width Modulator n Supports both Isolated and Non-Isolated Applications n Error Amplifier and Reference for Non-Isolated Applications n Programmable Oscillator Frequency n Programmable Soft-start n 80% Maximum Duty Cycle Limiter, Slope Compensation (-80 device) n 50% Maximum Duty Cycle Limiter, No Slope Compensation (-50 device) Features n Compatible with 12V ac adapters n Fully Compliant 802.3af Power Interface Port n 80V, 1Ω, 400 mA Internal MOSFET Packages n TSSOP-16 Block Diagram 20168401 © 2005 National Semiconductor Corporation DS201684 www.national.com LM5071 Block Diagram (Continued) www.DataSheet4U.com 20168402 FIGURE 1. Simplified Block Diagram Connection Diagram 20168403 16 Lead TSSOP Ordering Information Order Number LM5071MT-50 LM5071MTX-50 LM5071MT-80 LM5071MTX-80 Description 50% Duty Cycle Limit 50% Duty Cycle Limit 80% Duty Cycle Limit 80% Duty Cycle Limit NSC Package Type / Drawing TSSOP-16/MTC-16 TSSOP-16/MTC-16 TSSOP-16/MTC-16 TSSOP-16/MTC-16 Supplied As 92 units per rail 2500 units on tape and reel 92 units per rail 2500 units on tape and reel www.national.com 2 LM5071 Pin Descriptions Pin 1 2 Name VIN RSIG Description System high potential input. Signature resistor pin. Application Information www.DataSheet4U.com The diode “OR” of several lines entering the PD, it is the more positive input potential. Connect a resistor from VIN to this pin for signature detection. The resistor is in parallel with the UVLO resistors and should be valued accordingly. Connect the classification programming resistor from this pin to VEE. A resistor divider between the AUX voltage input to VEE programs the startup levels with a 2.5V threshold. A high value ( > 300kΩ) internal pull down resistor is present to pull the pin low if it is left open. In practice, the divider voltage should be set well above 2.5V by the programming resistors. An external resistor divider from VIN to UVLORTN programs the shutdown levels with a 2.00V threshold at the UVLO pin. Hysteresis is set by a switched internal 10uA current source that forces additional current into the resistor divider. Connect the bottom resistor of the resistor divider between the UVLO pin and this pin. Diode “OR’d” to the RJ45 connector and PSE’s –48V supply, it is the more negative input potential. The drain of the internal current limiting power MOSFET which connects VEE to the return path of the dc-dc converter. DC-DC converter gate driver output with 800mA peak sink current capability. When the auxiliary transformer winding (if used) raises the voltage on this pin above the regulation set point, the internal series pass regulator will shutdown, reducing the controller power dissipation. Inverting input of the internal error amplifi...

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