Power Over Ethernet PD Controller with Auxiliary Power Interface - LM5071


Power Over Ethernet PD Controller with Auxiliary Power Interface


Recommended alternative parts

  • LM5070  -  Integrated Power Over Ethernet PD Interface And PWM Controller
  • LM5072  -  Higher Transient Voltages (100V), Supplies More Current (750mA) And Compatible With Auxiliary Power


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.


  • Compatible with 12V AC Adapters
  • Fully Compliant 802.3af Power Interface Port
  • 80V, 1Ω, 400 mA Internal MOSFET
  • Detection Resistor Disconnect Function
  • Programmable Classification Current
  • Programmable Under-voltage Lockout with Programmable Hysteresis
  • Thermal Shutdown Protection
  • Auxiliary Power Enable Pin
  • Current Mode Pulse Width Modulator
  • Supports both Isolated and Non-Isolated Applications
  • Error Amplifier and Reference for Non-Isolated Applications
  • Programmable Oscillator Frequency
  • Programmable Soft-Start
  • 80% Maximum Duty Cycle Limiter, Slope Compensation (-80 device)
  • 50% Maximum Duty Cycle Limiter, No Slope Compensation (-50 device)


  • TSSOP-16

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Parametrics Compare all products in Powered Device

Duty Cycle (%)
Fault Response
Switching Frequency
rDS(on) per FET (Typ) (mOhms)
Auxiliary/Local Power Support
Driven/Active Clamp (Second Gate Drive)
PoE Current Limit (Min) (mA)
Error Amplifier
PD Power Level
PoE Inrush Limit (Typ) (mA)
PoE Standards Supported
PoE I/F & DC DC Control
Auxiliary Power Rails Supported
Frequency (Max) (kHz)
Approx. Price (US$)
LM5071 LM5070 LM5072
80     80     80    
Thermal Cycling     Thermal Cycling     Thermal Cycling    
Adjustable     Adjustable     IEEE    
1000     1000     700    
External Circuit        
No     No     No    
390     300     800    
Yes     Yes     Yes    
13W     13W     25W    
100     Programmable     Programmable    
802.3at Type 1 (802.3af)     802.3at Type 1 (802.3af)     802.3at Type 1 (802.3af)    
10-57V       9-100V    
1000     1000     1000    
1.30 | 1ku     1.30 | 1ku     1.70 | 1ku    

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