Power Over Ethernet PD Controller

LM5071 Power Over Ethernet PD Controller with Auxiliary Power Interface November 2005 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) 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 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 amplifier. The non-inverting input is internally connected to a 1.25V reference. COMP pull-up is provided by an internal 5K resistor which may be used to bias an opto-coupler transistor. Current sense input for current mode control and over-current protection. Current limiting is accomplished using a dedicated current sense comparator. If the CS pin voltage exceeds 0.5V the OUT pin switches low for cycle-by-cycle current limiting. CS is held low for 50ns after OUT switches high to blank leading edge current spikes. An external resistor connected from RT to ARTN sets the oscillator frequency. This pin will also accept narrow ac-coupled synchronization pulses from an external clock. An external capacitor and an internal 10uA current source set the soft-start ramp rate. RTN for sensitive analog circuitry including the SMPS current limit amplifier. 3 4 RCLASS AUX Classification resistor pin. Auxiliary input power startup pin. 5 UVLO Line under-voltage lockout. 6 7 8 9 10 UVLORTN Return for the external UVLO resistors. VEE RTN OUT VCC System low potential input. System return for the PWM converter. Output of the PWM controller. Output of the internal high voltage series pass regulator. Regulated output voltage is nominally 7.8V. Feedback signal. The output of the error amplifier and input to the Pulse Width Modulator. Current sense input. 11 12 13 FB COMP CS 14 RT / SYNC Oscillator timing resistor pin and synchronization input. SS ARTN Soft-start input. Analog PWM supply return. 15 16 3 www.national.com LM5071 Absolute Maximum Ratings (Note 1) If Military/Aerospace specified devices are required, please contact the National Semiconductor Sales Office/ Distributors for availability and specifications. VIN ,RTN to VEE RSIG to VIN AUX to VEE UVLO RCLASS to VEE ARTN to RTN VCC, OUT to ARTN All other inputs to ARTN -0.3V to 80V -12V to 0V -0.3V to 57V -0.3V to 13V -0.3V to 7V -0.3V to 0.3V -0.3V to 16V -0.3V to 7V ESD Rating Human Body Model Lead Temperature (Note 2) Wave (4 seconds) Infrared (10 seconds) Vapor Phase (75 seconds) 2000V 260˚C 240˚C 219˚C Operating Ratings VIN voltage External voltage applied to VCC 1.8V to 60V 8.1V to 15V Electrical Characteristics (Note 3) Specifications in standard type face are for TJ= +25˚C and those in boldface type apply over the full operating junction temperature range. Unless otherwise specified: VIN = 48V, VCC = 10V, RT = 30.3kΩ. Symbol Powered Interface IOS VCLSS(ON) VCLSS(OFF) ICLASS IDC Offset Current Signature Resistor Disable / Classification Current Turn On Classification Current Turn Off Classification Voltage Supply Current During Classification Supply Current During Normal Operation UVLO Pin Reference Voltage UVLO Hysteresis Current Softstart Release Softstart Release Hysteresis RDS(ON) ILEAK PowerFET Resistance SMPS Bias Current AUX Pin Threshold AUX Pin Threshold Hysteresis ZAUX IINRUSH ILIM ILIM Startup Regulator VinMin VccReg Operational VIN Input Voltage VCC Regulation VCC Current Limit AUX = 5V Open ckt (Note 4) 9.5 7.5 15 7.8 20 8.1 V V mA AUX Pin Input Impedance Inrush Current Limit DC Current Limit DC Current Limit VIN < 10.0V VIN with respect to VEE VIN with respect to VEE With respect to VEE VIN =17V OUT floating VIN > 27V VIN > UVLO RTN falling with respect to VEE RTN rising with respect to VEE I = 350mA, VIN = 48V VEE = 0V, VIN = RTN = 57V AUX pin rising with respect to VEE AUX pin falling with respect to VEE AUX = 0.5V VEE = 0V, RTN = 3.0V VEE = 0V, RTN = 3.0V, Temp = 0˚C to 85˚C VEE = 0V, RTN = 3.0V, Temp = -40˚C to 125˚C 70 350 325 2.4 0.4 2.5 0.5 350 100 390 390 130 420 420 1.95 8.0 1.2 0.8 10.0 23.5 1.43 11.5 25.0 1.5 0.5 1 2.00 10 1.45 1.1 1 10 12.5 26.5 1.57 1.5 1.9 2.05 11.5 1.7 1.3 2.2 100 2.65 0.6 uA V V V mA mA V uA V V Ω uA V V kΩ mA mA mA Parameter Conditions Min Typ Max Units www.national.com 4 LM5071 Electrical Characteristics (Note 3) Symbol VCC Supply VCC UVLO (Rising) Parameter (Continued) Specifications in standard type face are for TJ= +25˚C and those in boldface type apply over the full operating junction temperature range. Unless otherwise specified: VIN = 48V, VCC = 10V, RT = 30.3kΩ. Conditions Min Typ Max Units VccReg VccReg – – 100mV 300mV 5.9 Cload = 0 6.25 1.5 4 75 FB = COMP FB=1.5V COMP=1V CS step from 0 to 0.6V, time to onset of OUT transition (90%) 0.44 1.219 1.212 5 20 20 0.5 55 25 7 175 505 10 200 580 3.1 COMP set to 2V CS stepped 0 to 0.4V, time to onset of OUT transition low COMP=0V 80 50 0.33 4.5 COMP= 0V Delta increase at PWM Comparator to CS Iout = 50mA, VCC - VOUT Iout = 100mA Cload = 1nF Cload = 1nF 0.6 5.4 1.1 105 6.3 1.5 V mA mV 25 55 13 225 665 3.8 0.56 1.281 1.288 6.6 3 V mA MHz dB V mA ns V ns Ω uA KHz KHz V ns VCC UVLO (Falling) Supply Current (Icc) Error Amplifier GBW Gain Bandwidth DC Gain Input Voltage COMP Sink Capability Current Limit ILIM Delay to Output Cycle by Cycle Current Limit Threshold Voltage Leading Edge Blanking Time CS Sink Impedance (clocked) Softstart Softstart Current Source Oscillator(Note 5) Frequency1 (RT = 30.3K) Frequency2 (RT = 10.5K) Sync threshold PWM Comparator Delay to Output Min Duty Cycle Max Duty Cycle (-80 Device) Max Duty Cycle (-50 Device) COMP to PWM Comparator Gain COMP Open Circuit Voltage COMP Short Circuit Current Slope Compensation Slope Comp Amplitude (LM5071-80 Device Only) Output Section Output High Saturation Output Low Saturation Rise time Fall time 0 % % % 0.25 0.25 15 15 0.75 0.75 V V ns ns 5 www.national.com LM5071 Electrical Characteristics (Note 3) Symbol Thermal Shutdown Tsd Thermal Shutdown Hysteresis Thermal Resistance θJA Junction to Ambient Thermal Shutdown Temp. Parameter (Continued) Specifications in standard type face are for TJ= +25˚C and those in boldface type apply over the full operating junction temperature range. Unless otherwise specified: VIN = 48V, VCC = 10V, RT = 30.3kΩ. Conditions Min Typ 165 25 Max Units ˚C ˚C MT Package 125 ˚C/W Note 1: Absolute Maximum Ratings are limits beyond which damage to the device may occur