19-5142; Rev 0; 1/10 TION KIT EVALUA BLE AVAILA Single-Port, 40W, IEEE 802.3af/at PSE Controller with Integrated MOSFET The MAX5971A is a single-port, power-sourcing equipment (PSE) power controller designed for use in IEEE® 802.3af/at-compliant PSE. This device provides powered device (PD) discovery, classification, current limit, and DC and AC load-disconnect detections. The MAX5971A operates automatically without the need for any software programming and features an integrated power MOSFET and sense resistor. The device also supports new Class 5 and 2-event classification for detection and classification of high-power PDs. The MAX5971A provides up to 40W to a single port (Class 5 enabled) and still provides highcapacitance detection for legacy PDs. The MAX5971A provides input undervoltage lockout (UVLO), input overvoltage lockout, overtemperature detection, output voltage slew-rate limit during startup, and LED status indication. The MAX5971A is available in a space-saving, 28-pin TQFN (5mm x 5mm) power package, and is rated for the extended (-40NC to +85NC) temperature range. Applications Single-Port PSE End-Point Applications Single-Port PSE Power Injectors (Midspan Applications) Features S IEEE 802.3af/at Compliant S Up to 40W for Single-Port PSE Applications S Integrated 0.5I Power MOSFET and Sense Resistor S PD Detection and Classification S Programmable Current Limit for Class 5 PDs S High-Capacitance Detection for Legacy Devices S Supports Both DC and AC Load Removal Detections S Current Foldback and Duty Cycle-Controlled Current Limit S LED Indicator for Port Status S Direct Fast-Shutdown Control Capability S Space-Saving, 28-Pin TQFN (5mm x 5mm) Package Ordering Information PART MAX5971AETI+ TEMP RANGE PIN-PACKAGE -40NC to +85NC 28 TQFN-EP* +Denotes a lead(Pb)-free/RoHS-compliant package. *EP = Exposed pad. Typical Operating Circuit Switches/Routers Industrial Automation Equipment Wireless LAN Access Point/WiMAX™ Base Station PSE OUTPUT -54V AGND VEE OUT VEE_DIG LED OUTP MAX5971A PWMEN LEGACY DET MIDSPAN ILIM1 OSC ILIM2 EN IEEE is a registered service mark of the Institute of Electrical and Electronics Engineers, Inc. WiMAX is a trademark of WiMAX Forum. ________________________________________________________________ Maxim Integrated Products 1 For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com. MAX5971A General Description MAX5971A Single-Port, 40W, IEEE 802.3af/802.3at PSE Controller with Integrated MOSFET ABSOLUTE MAXIMUM RATINGS (Voltages referenced to VEE, unless otherwise noted.) AGND, DET, LED...................................................-0.3V to +80V OUT.......................................................-0.3V to (VAGND + 0.3V) OUTP........................................................-6V to (VAGND + 0.3V) VEE_DIG................................................................-0.3V to +0.3V OSC..........................................................................-0.3V to +6V EN, PWMEN, MIDSPAN, LEGACY, ILIM1, ILIM2.....-0.3V to +4V Maximum Current Into LED.................................................40mA Maximum Current Into OUT.......................... Internally regulated Continuous Power Dissipation (TA = +70NC) 28-Pin TQFN (derate 34.5mW/NC above +70NC).......2758mW Package Thermal Resistance (Note 1) BJA. ..............................................................................29NC/W BJC.................................................................................2NC/W Operating Temperature Range........................... -40NC to +85NC Storage Temperature Range............................. -65NC to +150NC Junction Temperature......................................................+150NC Lead Temperature (soldering, 10s).................................+300NC Soldering Temperature (reflow).......................................+260NC Note 1: Package thermal resistances were obtained using the method described in JEDEC specification JESD51-7, using a fourlayer board. For detailed information on package thermal considerations, refer to www.maxim-ic.com/thermal-tutorial. Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability. ELECTRICAL CHARACTERISTICS (VAGND - VEE = 32V to 60V, TA = -40NC to +85NC, all voltages are referenced to VEE, unless otherwise noted. Typical values are at VAGND - VEE = +54V, TA = +25NC. Currents are positive when entering the pin and negative otherwise.) (Note 2) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS 60 V 2.5 4 mA POWER SUPPLIES Operating Voltage Range Supply Current VAGND VAGND - VEE 32 IEE VOUT = VEE, all logic inputs unconnected, measured at AGND in power mode ILIM Maximum ILOAD allowed during current-limit conditions, VOUT = 0V (Note 3) CURRENT LIMIT Current Limit Class 0, 1, 2, 3 400 420 441 Class 4 684 720 756 Class 5 if ILIM1 = VEE, ILIM2 = unconnected 807 850 893 Class 5 if ILIM1 = unconnected, ILIM2 = VEE 855 900 945 Class 5 if ILIM1 = VEE, ILIM2 = VEE 902 950 998 mA Foldback Initial OUT Voltage VFLBK_ST VAGND - VOUT below which the current limit starts folding back 27 V Foldback Final OUT Voltage VFLBK_END VAGND - VOUT below which the current limit reaches ITH_FB 10 V VOUT = VAGND 166 mA Minimum Foldback Current Limit Threshold ITH_FB 2 _______________________________________________________________________________________ Single-Port, 40W, IEEE 802.3af/802.3at PSE Controller with Integrated MOSFET (VAGND - VEE = 32V to 60V, TA = -40NC to +85NC, all voltages are referenced to VEE, unless otherwise noted. Typical values are at VAGND - VEE = +54V, TA = +25NC. Currents are positive when entering the pin and negative otherwise.) (Note 2) PARAMETER SYMBOL CONDITIONS MIN TYP MAX Class 0, 1, 2, 3 351 370 389 Class 4 602 634 666 Class 5 if ILIM1 = VEE, ILIM2 = unconnected 710 748 785 Class 5 if ILIM1 = unconnected, ILIM2 = VEE 752 792 832 Class 5 if ILIM1 = VEE, ILIM2 = VEE 794 836 878 TA = +25NC 0.5 0.9 TA = +85NC 0.6 1.3 UNITS OVERCURRENT Overcurrent Threshold ICUT Overcurrent threshold allowed for t P tFAULT, VOUT = 0V (Note 3) mA INTERNAL POWER DMOS On-Resistance RDS(ON) Power-Off OUT Leakage Current IOUT_LEAK Measured from OUT to VEE, IOUT = 100mA I VEN = VEE, VOUT = VAGND 10 FA SUPPLY MONITORS VEE Undervoltage Lockout VEE_UVLO VEE Undervoltage Lockout Hysteresis VEE_UVLOH VEE Overvoltage Lockout VEE_OV VEE Overvoltage Lockout Hysteresis VEE_OVH VAGND - VEE, VAGND increasing 28.5 V 3 V 62.5 V 1 V Port is shutdown and device resets if the junction temperature exceeds this limit, temperature increasing 150 NC 20 NC Port is shutdown if: VAGND - VEE < VEE_ UVLO - VEE_UVLOH VAGND - VEE > VEE_OV, VAGND increasing Thermal Shutdown Threshold TSHD Thermal Shutdown Hysteresis TSHDH Temperature decreasing IBOUT VOUT = VAGND, probing phases OUTPUT MONITOR OUT Input Current IDIS OUTP discharge current, detection and classification off, port shutdown, VOUTP = VAGND - 2.8V 200 Short to VEE Detection Threshold DCNTH VOUT - VEE, VOUT decreasing, enabled during detection 1.5 Short to VEE Detection Threshold Hysteresis DCNHY Idle Pullup Current at OUT 2.0 6 FA 265 FA 2.5 V 220 mV LOAD DISCONNECT DC Load-Disconnect Threshold IDCTH Minimum load current allowed before disconnect (DC disconnect active), VOUT = 0V AC Load-Disconnect Threshold IACTH Current into DET, for IDET < IACTH the port powers off (AC disconnect active) 5 7.5 10 mA 115 130 145 FA _______________________________________________________________________________________ 3 MAX5971A ELECTRICAL CHARACTERISTICS (continued) MAX5971A Single-Port, 40W, IEEE 802.3af/802.3at PSE Controller with Integrated MOSFET ELECTRICAL CHARACTERISTICS (continued) (VAGND - VEE = 32V to 60V, TA = -40NC to +85NC, all voltages are referenced to VEE, unless otherwise noted. Typical values are at VAGND - VEE = +54V, TA = +25NC. Currents are positive when entering the pin and negative otherwise.) (Note 2) PARAMETER SYMBOL MIN TYP MAX UNITS 3.85 4 4.2 V Measured at OSC 26 32 39 FA VOSC - VEE > VACD_EN to activate AC disconnect 280 330 380 mV tDISC Time from IRSENSE < IDCTH (DC disconnect active) or IDET < IACTH (AC disconnect active) to gate shutdown 300 400 ms Detection Probe Voltage (First Phase) VDPH1 VAGND - VDET during the first detection phase 3.8 4 4.2 V Detection Probe Voltage (Second Phase) VDPH2 VAGND - VDET during the second detection phase 9 9.3 9.6 V Current-Limit Protection IDLIM VDET = VAGND during detection, measure current through DET 1.50 1.75 2.00 mA Short-Circuit Threshold VDCP If VAGND - VOUT < VDCP after the first detection phase a short circuit to AGND is detected. 1 V Open-Circuit Threshold ID_OPEN First point measurement current threshold for open condition 20 FA Triangular Wave Peak-to-Peak Voltage Amplitude AMPTRW OSC Pullup/Pulldown Currents IOSC ACD_EN Threshold Load Disconnect Timer VACD_EN CONDITIONS Measured at DET, referred to AGND DETECTION Resistor Detection Window Resistor Rejection Window RDOK RDBAD (Note 4) 19 26.5 Detection rejects lower values 15.5 kI kI Detection rejects higher values 32 VAGND - VDET during classification 16 20 V VDET = VAGND, during classification measure current through DET 65 80 mA CLASSIFICATION Classification Probe Voltage Current-Limit Protection Classification Current Thresholds Mark Event Voltage Mark Event Current Limit VCL IClLIM ICL VMARK IMARK_LIM Classification current thresholds between classes Class 0, Class 1 5.5 6.5 7.5 Class 1, Class 2 13.0 14.5 16.0 Class 2, Class 3 21 23 25 Class 3, Class 4 31 33 35 Class 4 upper limit (Note 5) 45 48 51 mA VAGND - VDET during mark event 8 10 V VDET = VAGND, during mark event measure current through DET 55 80 mA 4 _______________________________________________________________________________________ Single-Port, 40W, IEEE 802.3af/802.3at PSE Controller with Integrated MOSFET (VAGND - VEE = 32V to 60V, TA = -40NC to +85NC, all voltages are referenced to VEE, unless otherwise noted. Typical values are at VAGND - VEE = +54V, TA = +25NC. Currents are positive when entering the pin and negative otherwise.) (Note 2) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS 0.8 V DIGITAL INPUTS/OUTPUTS (Voltages referenced to VEE) Digital Input Low VIL Digital Input High VIH 2.4 IPU Pullup current to internal digital supply to set default values LED Output Low Voltage VLED_LOW LED Output Leakage ILED_LEAK Internal Input Pullup Current 3 V 5 7 FA ILED = 10mA, PWM disabled, port power-on 0.8 V PWM disabled, shutdown mode, VLED = 60V 10 FA PWM Frequency 25 kHz PWM Duty Cycle 6.25 % TIMING Startup Time tSTART Time during which a current limit set to 420mA is allowed, starts when power is turned on 50 60 70 ms Fault Time tFAULT Maximum allowed time for an overcurrent condition set by ICUT after startup 50 60 70 ms Detection Reset Time tME Time allowed for the port voltage to reset before detection starts 80 90 ms Detection Time tDET Maximum time allowed before detection is completed 330 ms Midspan Mode Detection Delay tDMID Classification Time tCLASS Mark Event Time Time allowed for mark event VEEUVLO Turn-On Delay Restart Timer 2 Time allowed for classification tDLY tRESTART Time VAGND must be above the VEEUVLO thresholds before the device operates Time the device waits before turning on after an overcurrent fault 7 2.2 2.4 s 19 23 ms 9 11 ms 5.2 ms 16 x tFAULT ms Note 2: All devices are production tested at TA = +25NC. Limits at TA = -40NC and +85NC are guaranteed by design. Note 3: If ILIM1 and ILIM2 are both unconnected, Class 5 detection is disabled. See the Class 5 PD Classification section and Table 3 for details and settings. Note 4: RDOK = (VOUT2 - VOUT1)/(IDET2 - IDET1). VOUT1, VOUT2, IDET2, and IDET1 represent the voltage at OUT and the current at DET during phase 1 and 2 of the detection, respectively. Note 5: If Class 5 is enabled, this is the classification current thresholds from Class 4 to Class 5. _______________________________________________________________________________________ 5 MAX5971A ELECTRICAL CHARACTERISTICS (continued) Typical Operating Characteristics (TA = +25°C, unless otherwise noted.) ANALOG SUPPLY CURRENT vs. INPUT VOLTAGE SUPPLY CURRENT (mA) 2.6 2.5 2.4 MEASURED AT AGND 2.6 2.5 2.4 30.0 MAX5971A toc03 2.7 UNDERVOLTAGE LOCKOUT (V) MEASURED AT AGND VEE UNDERVOLTAGE LOCKOUT vs. TEMPERATURE MAX5971A toc02 ANALOG SUPPLY CURRENT vs. TEMPERATURE MAX5971A toc01 2.7 SUPPLY CURRENT (mA) 29.5 29.0 28.5 28.0 27.5 2.3 32 36 40 44 48 52 56 2.3 60 27.0 -15 -40 VAGND - VEE (V) 10 35 60 85 10 35 TEMPERATURE (°C) INTERNAL FET RESISTANCE vs. TEMPERATURE 63.5 FET RESISTANCE (mΩ) 63.0 62.5 62.0 61.5 61.0 MAX5971A toc05 1000 MAX5971A toc04 64.0 UNDERVOLTAGE LOCKOUT (V) -15 -40 TEMPERATURE (°C) VEE OVERVOLTAGE LOCKOUT vs. TEMPERATURE 800 600 400 60.5 60.0 200 -40 -15 10 35 60 85 -40 -15 10 35 60 TEMPERATURE (°C) TEMPERATURE (°C) FOLDBACK CURRENT-LIMIT THRESHOLD vs. OUTPUT VOLTAGE DC DISCONNECT THRESHOLD vs. TEMPERATURE CLASS 4 600 500 400 300 CLASS 0, 1, 2, 3 200 100 0 0 10 20 VAGND - VOUT (V) 30 40 85 MAX5971A toc07 700 7.4 DC DISCONNECT THRESHOLD (mA) MAX5971A toc06 800 IRSENSE (mA) MAX5971A Single-Port, 40W, IEEE 802.3af/802.3at PSE Controller with Integrated MOSFET 7.2 7.0 6.8 6.6 6.4 -40 -15 10 35 60 TEMPERATURE (°C) 6 _______________________________________________________________________________________ 85 60 85 Single-Port, 40W, IEEE 802.3af/802.3at PSE Controller with Integrated MOSFET SHORT-CIRCUIT RESPONSE TIME OVERCURRENT TIMEOUT (240Ω TO 138Ω) MAX5971A toc09 MAX5971A toc08 VAGND - VOUT 20V/div VAGND - VOUT 20V/div 0V 0V IOUT 200mA/div IOUT 200mA/div 0mA 0mA 20ms/div 20ms/div SHORT-CIRCUIT TRANSIENT RESPONSE EN TO OUT TURN-OFF DELAY MAX5971A toc10 MAX5971A toc11 VAGND - VOUT 20V/div VAGND - VOUT 20V/div 0V 0V IOUT 200mA/div 0mA IOUT 5A/div 0mA VEN 5V/div 0V 10µs/div 100µs/div ZERO-CURRENT DETECTION WAVEFORM WITH DC DISCONNECT ENABLED ZERO-CURRENT DETECTION WAVEFORM WITH AC DISCONNECT ENABLED MAX5971A toc12 MAX5971A toc13 VAGND - VOUT 20V/div 0V VAGND - VOUT 20V/div 0V IOUT 100mA/div 0mA IOUT 100mA/div 0mA 100ms/div 100ms/div _______________________________________________________________________________________ 7 MAX5971A Typical Operating Characteristics (continued) (TA = +25°C, unless otherwise noted.) MAX5971A Single-Port, 40W, IEEE 802.3af/802.3at PSE Controller with Integrated MOSFET Typical Operating Characteristics (continued) (TA = +25°C, unless otherwise noted.) OVERCURRENT RESTART DELAY STARTUP WITH A VALID PD MAX5971A toc14 MAX5971A toc15 VAGND - VOUT 20V/div VAGND - VOUT 20V/div 0V 0V IOUT 200mA/div IOUT 100mA/div 0mA 0mA 400ms/div 100ms/div DETECTION WITH INVALID PD (25kΩ TO 10µF) DETECTION WITH INVALID PD (15kΩ) MAX5971A toc16a VAGND - VOUT 1V/div MAX5971A toc16b VAGND - VOUT 5V/div 0V 0V IOUT 1mA/div 0mA IOUT 1mA/div 0mA 40ms/div 100ms/div DETECTION WITH INVALID PD (OPEN CIRCUIT) DETECTION WITH INVALID PD (33kΩ) MAX5971A toc16d MAX5971A toc16c VAGND - VOUT 5V/div VAGND - VOUT 5V/div 0V 0V IOUT 1mA/div 0mA 100ms/div IOUT 1mA/div 0mA 100ms/div 8 _______________________________________________________________________________________ Single-Port, 40W, IEEE 802.3af/802.3at PSE Controller with Integrated MOSFET STARTUP IN MIDSPAN WITH A VALID PD DETECTION IN MIDSPAN WITH INVALID PD (15kΩ) MAX5971A toc17 MAX5971A toc18a VAGND - VOUT 20V/div 0V VAGND - VOUT 5V/div 0V IOUT 100mA/div 0mA IOUT 1mA/div 0mA 100ms/div 400ms/div DETECTION IN MIDSPAN WITH INVALID PD (33kΩ) MAX5971A toc18b DETECTION IN OUTPUT SHORTED TO AGND MAX5971A toc19 VAGND - VOUT 5V/div VAGND - VOUT 5V/div 0V 0V IOUT 1mA/div 0mA IOUT 1mA/div 0mA 40ms/div 400ms/div CLASSIFICATION WITH DIFFERENT PD CLASSES (0 TO 3) CLASSIFICATION WITH DIFFERENT PD CLASSES (4 AND 5) MAX5971A toc20a MAX5971A toc20b VAGND - VOUT 10V/div 0V VAGND - VOUT 10V/div 0V CLASS 3 CLASS 2 0mA CLASS 1 CLASS 0 40ms/div CLASS 5 CLASS 4 IOUT 10mA/div IOUT 20mA/div 0mA 40ms/div _______________________________________________________________________________________ 9 MAX5971A Typical Operating Characteristics (continued) (TA = +25°C, unless otherwise noted.) MAX5971A Single-Port, 40W, IEEE 802.3af/802.3at PSE Controller with Integrated MOSFET Typical Operating Characteristics (continued) (TA = +25°C, unless otherwise noted.) STARTUP USING 2-EVENT CLASSIFICATION WITH A VALID PD MAX5971A toc21 LED DETECTION FAULT WITH PWM ENABLED MAX5971A toc22a VAGND - VOUT 20V/div 0V VAGND - VOUT 10V/div 0V IOUT 500mA/div 0mA IOUT 100mA/div VAGND - VLED 20V/div 0mA 0V 100ms/div 200ms/div LED DETECTION FAULT WITH PWM DISABLED MAX5971A toc22b VAGND - VOUT 10V/div 0V IOUT 500mA/div 0mA LED OVERCURRENT FAULT WITH PWM ENABLED MAX5971A toc23a VAGND - VOUT 50V/div 0V IOUT 500mA/div 0mA VAGND - VLED 20V/div 0V VAGND - VLED 20V/div 0V 200ms/div 200ms/div LED OVERCURRENT FAULT WITH PWM DISABLED LED PWM TIMING AND DUTY CYCLE MAX5971A toc23b VAGND - VOUT 50V/div 0V IOUT 500mA/div 0mA MAX5971A toc24 VAGND - VOUT 50V/div 0V IOUT 500mA/div 0mA VAGND - VLED 20V/div VAGND - VLED 20V/div 0V 0V 200ms/div 10µs/div 10 ������������������������������������������������������������������������������������� Single-Port, 40W, IEEE 802.3af/802.3at PSE Controller with Integrated MOSFET AGND N.C. OSC N.C. LED N.C. I.C. TOP VIEW 21 20 19 18 17 16 15 N.C. 22 14 EN DET 23 13 LEGACY N.C. 24 12 VEE_DIG 11 I.C. 10 I.C. 9 I.C. 8 I.C. OUTP 25 MAX5971A OUT 26 OUT 27 *EP + 4 5 6 7 ILIM2 PWMEN MIDSPAN VEE 3 ILIM1 2 VEE 1 VEE N.C. 28 THIN QFN *EXPOSED PAD, CONNECT TO AGND. Pin Description PIN 1, 2, 3 NAME VEE FUNCTION Analog Low-Side Supply Input. Bypass with an external 100V, 47FF capacitor in parallel with a 100V, 0.1FF ceramic capacitance between AGND and VEE. ILIM1 Class 5 Current-Limit Digital Adjust 1. Referenced to VEE. ILIM1 is internally pulled up to the digital supply. Use ILIM1 with ILIM2 to enable Class 5 operation and to adjust the Class 5 current-limit value. See the Electrical Characteristics table and Table 3 in the Class 5 PD Classification section for details. 5 ILIM2 Class 5 Current-Limit Digital Adjust 2. Referenced to VEE. ILIM2 is internally pulled up to the digital supply. Use ILIM2 with ILIM1 to enable Class 5 operation and to adjust the Class 5 current-limit value. See the Electrical Characteristics table and Table 3 in the Class 5 PD Classification section for details. 6 PWMEN PWM Control Logic Input. Referenced to VEE. PWMEN is internally pulled up to the digital supply. Leave unconnected to enable the internal PWM to drive the LED pin. Force low to disable the internal PWM. 4 7 MIDSPAN 8–11, 15 I.C. 12 VEE_DIG Detection Collision Avoidance Logic Input. Referenced to VEE. MIDSPAN is internally pulled up to the digital supply. Leave unconnected to activate the detection collision avoidance circuitry for midspan PSE systems. Force low to disable this function for an end-point PSE system. The MIDSPAN logic level latches after the device is powered up or after a reset condition. Internally Connected. Connect I.C. to VEE. Digital Low-Side Supply Input. Connect to VEE externally. ______________________________________________________________________________________ 11 MAX5971A Pin Configuration MAX5971A Single-Port, 40W, IEEE 802.3af/802.3at PSE Controller with Integrated MOSFET Pin Description (continued) PIN NAME FUNCTION 13 LEGACY Legacy Detection Logic Input. Referenced to VEE. LEGACY is internally pulled up to the digital supply. Leave unconnected to activate the legacy PD detection. Force low to disable this function. The LEGACY logic level latches after the device is powered up or after a reset condition. 14 EN Enable Input. Referenced to VEE. EN is internally pulled up to the digital supply. Leave unconnected to enable the device. Force low for at least 40Fs to reset the device. The MIDSPAN, OSC, and LEGACY states latch-in when the reset condition is removed (low-to-high transition). 16, 18, 20, 22, 24, 28 N.C. No Connection. Not internally connected. Leave N.C. unconnected. LED LED Indicator Open-Drain Output. Referenced to VEE. LED can sink 10mA and can drive an external LED directly. Blinking functionality is provided to signal different conditions (see the PWM and LED Signals section). Connect LED to AGND externally (see Figures 6 and 7) or to an external supply (if available) through a series resistance. 19 OSC AC-Disconnect Triangular Wave Output. Bypass with a 100nF (Q10% tolerance) external capacitor to VEE to enable the AC disconnect function. Connect OSC to VEE to disable the AC disconnect function and to activate the DC disconnect function. The OSC state latches after the device is powered up or after a reset condition. 21 AGND 17 High-Side Supply Input DET Detection/Classification Voltage Output. DET is used to set the detection mark event and classification probe voltages and for the AC current sensing when using the AC disconnect function. To use the AC disconnect function, place a 1kI and 0.47FF RC series in parallel with the external protection diode to OUTP (see Figure 7). 25 OUTP Port Pullup Output. OUTP is used to pull up the port voltage to AGND when needed. If AC disconnect is used, connect OUTP to the anode of the AC-blocking diode. If AC disconnect is not used, connect OUTP to OUT (see Figures 6 and 8). Bypass OUTP to AGND with a 100V, 0.1FF ceramic capacitor. 26, 27 OUT Integrated MOSFET Output. If DC disconnect is used, connect the port output to OUT (see Figures 6 and 8). If the AC disconnect function is used, connect OUT to the cathode of the AC-blocking diode (see Figure 7). — EP 23 Exposed Pad. Connect EP to VEE externally. See the Layout Procedure section for details. 12 ������������������������������������������������������������������������������������� Single-Port, 40W, IEEE 802.3af/802.3at PSE Controller with Integrated MOSFET OSC CURRENT SENSING OSC STATUS MONITOR VOLTAGE PROBING AND CURRENT-LIMIT CONTROL TRIANGLE WAVE GENERATOR EN AGND OUTP LEGACY MIDSPAN DETECTION AND CLASSIFICATION CONTROL PORT STATE MACHINE (SM) REGISTER FILE VOLTAGE SENSING 9-BIT ADC AC DISCONNECT ENABLE CENTRAL LOGIC UNIT (CLU) AGND VEE DET ANALOG BIAS AND SUPPLY MONITOR OUT FOLDBACK CONTROL A=1 GATE DRIVE INTERNAL SUPPLIES AC DETECTOR AC DISCONNECT SIGNAL (ACD) VOLTAGE REFERENCES ACD REFERENCE CURRENT CURRENT REFERENCES THRESHOLD SETTINGS LED PWM MAX5971A PWMEN Detailed Description The MAX5971A is a single-port, PSE power controller designed for use in IEEE 802.3af/IEEE 802.3at-compliant PSE. This device provides PD discovery, classification, current limit, and DC and AC load-disconnect detections. The MAX5971A operates automatically without the need for any software programming and features an integrated power MOSFET and sense resistor. The device also supports new Class 5 and 2-event classification for detection and classification of high-power PDs. The MAX5971A provides up to 40W to a single port (Class 5 enabled) and still provides high-capacitance detection for legacy PDs. INTERNAL MOSFET CURRENT LIMIT, OVERCURRENT, AND OPENCIRCUIT SENSING, AND FOLDBACK CONTROL INTERNAL RSENSE CLASS 5 ENABLE/DISABLE, OVERCURRENT AND CURRENT LIMIT CONTROL ILIM1 ILIM2 The MAX5971A provides input UVLO, input overvoltage lockout, overtemperature detection, output voltage slewrate limit during startup, and LED status indication. Reset The MAX5971A is reset by any of the following conditions: 1) Power-up. Reset condition is cleared once VEE rises above the UVLO threshold. 2) Hardware reset. Reset occurs once the EN input is driven low (> 40µs typ.) any time after power-up. The device exits the reset condition once the EN input is driven high again. 3) Thermal shutdown. The device enters thermal shutdown at 150NC. The device exits thermal shutdown and is reset once the temperature drops below 130NC. ______________________________________________________________________________________ 13 MAX5971A Simplified Diagram MAX5971A Single-Port, 40W, IEEE 802.3af/802.3at PSE Controller with Integrated MOSFET During a reset, the MAX5971A latches in the state of MIDSPAN, LEGACY, and OSC. During normal operation, changes to these inputs are ignored. During detection, the MAX5971A keeps the internal MOSFET off and forces two probe voltages through DET. The current through DET is measured as well as the voltage at OUT. A two-point slope measurement is used, as specified by the IEEE 802.3af/802.3at standard, to verify the device connected to the port. Midspan Mode In midspan mode, the device adopts cadence timing during the detection phase. When cadence timing is enabled and a failed detection occurs, the port waits between 2s and 2.4s before attempting to detect again. Midspan mode is activated by setting MIDSPAN high and then powering or resetting the device. By default, the MIDSPAN input is internally pulled high. Force MIDSPAN low to disable this function. An external diode, in series with the DET input, restricts PD detection to the first quadrant as specified by the IEEE 802.3af/802.3at standard. To prevent damage to non-PD devices, and to protect itself from an output short circuit, the MAX5971A limits the current into DET to less than 2mA maximum during PD detection. In midspan mode, the MAX5971A waits at least 2.0s before attempting another detection cycle after every failed detection. The first detection, however, happens immediately after exiting a reset condition. Automatic Operation The MAX5971A operates automatically after the reset condition is cleared. The device performs detection and classification, and powers up the port automatically once a valid PD is detected at the port. If a valid PD is not connected at the port, the MAX5971A repeats the detection routine continuously until a valid PD is connected. High-Capacitance Detection The status of the LEGACY input is latched during powerup or after reset condition is cleared. The LEGACY input is internally pulled high enabling high-capacitance detection. Unless high-capacitance detection is needed, connect LEGACY to VEE to disable this function. If highcapacitance detection is enabled, PD signature capacitances up to 47FF (typ) are accepted. PD Detection During normal operation, the MAX5971A probes the output for a valid PD. A valid PD has a 25kI discovery signature characteristic as specified in the IEEE 802.3af/802.3at standard. Table 1 shows the IEEE 802.3at specification for a PSE detecting a valid PD signature. Table 1. PSE PI Detection Modes Electrical Requirements (IEEE 802.3at) PARAMETER SYMBOL MIN MAX UNITS ADDITIONAL INFORMATION Open-circuit voltage VOC 30 V In detection mode only Short-circuit current ISC 5 mA In detection mode only 10 V Valid test voltage VVALID 2.8 Voltage difference between test points DVTEST 1 V tBP 2 ms Time between any two test points Slew rate VSLEW 0.1 V/Fs Accept signature resistance RGOOD 19 26.5 kI Reject signature resistance RBAD < 15 > 33 kI Open-circuit resistance ROPEN 500 Accept signature capacitance CGOOD Reject signature capacitance CBAD 10 Signature offset voltage tolerance VOS 0 2.0 V Signature offset current tolerance IOS 0 12 FA This timing implies a 500Hz maximum probing frequency kI 150 nF FF 14 ������������������������������������������������������������������������������������� Single-Port, 40W, IEEE 802.3af/802.3at PSE Controller with Integrated MOSFET During the PD classification mode, the MAX5971A forces a probe voltage (-18V typ) at DET and measures the current into DET. The measured current determines the class of the PD. If the ILIM1 and ILIM2 pins are both left unconnected, the MAX5971A classifies the PD based on Table 33.9 of the IEEE 802.3at standard (see Table 2). If the measured current exceeds 51mA, the MAX5971A does not power the PD, but returns to the idle state before attempting a new detection cycle. Class 5 PD Classification The MAX5971A supports high power beyond the IEEE 802.3at standard by providing an additional classification (Class 5) if needed. To enable Class 5 detection and select the corresponding current-limit/overcurrent Table 2. PSE Classification of a PD (Table 33.9 of the IEEE 802.3at Standard) MEASURED ICLASS (mA) CLASSIFICATION 0 to 5 Class 0 > 5 and < 8 Can be Class 0 or 1 8 to 13 Class 1 > 13 and < 16 Either Class 1 or 2 16 to 21 Class 2 > 21 and < 25 Either Class 2 or 3 25 to 31 Class 3 > 31 and <35 Either Class 3 or 4 35 to 45 Class 4 > 45 and < 51 Either Class 4 or Invalid thresholds, ILIM1 and ILIM2 must be set based on the combinations detailed in Table 3. Once Class 5 is enabled, during classification, if the MAX5971A detects currents in excess of the Class 4 upper limit threshold, the PD is classified as a Class 5 powered device. The PD is guaranteed to be classified as a Class 5 device for any classification current from 51mA up to the classification current-limit threshold. The Class 5 overcurrent threshold and current limit is set with ILIM1 and ILIM2. ILIM1 and ILIM2 are both referenced to VEE and are internally pulled up to the digital supply. Leave ILIM1 and ILIM2 unconnected to disable Class 5 detection and to be fully compliant to IEEE 802.3at standard classification. Class 5 detection is enabled, and the corresponding overcurrent threshold and current limit is adjusted, by connecting one or both to VEE (see Table 3). 2-Event PD Classification If the result of the first classification event is Class 0 through Class 3, then only a single classification event occurs as shown in Figure 1. However, if the result is Class 4 or Class 5 (when enabled), the device performs a second classification event as shown in Figure 2. Between the classification cycles, the MAX5971A performs a first and second mark event as required by the IEEE 802.3at standard, forcing a -9.0V probing voltage at DET. Powered State When the MAX5971A enters a powered state, the tFAULT and tDISC timers are reset. When the startup timer has timed out, the device enters a normal powered condition, allowing power delivery to the PD . Table 3. Class 5 Overcurrent Threshold and Current-Limit Settings ILIM1 CONFIGURATION ILIM2 CONFIGURATION OVERCURRENT THRESHOLD (mA) CURRENT LIMIT (mA) Unconnected Unconnected Class 5 disabled Class 5 disabled Unconnected VEE 748 850 VEE Unconnected 792 900 VEE VEE 836 950 ______________________________________________________________________________________ 15 MAX5971A Powered Device Classification (PD Classification) MAX5971A Single-Port, 40W, IEEE 802.3af/802.3at PSE Controller with Integrated MOSFET 80ms 150ms tDET(1) 150ms tDET(2) 19ms tCLASS t 0V -4V -9.3V -18V -48V VOUT Figure 1. Detection, Classification, and Port Power-Up Sequence 9ms 9ms 80ms 150ms 150ms 19ms 19ms tDET(1) tDET(2) tCLASS(1) tCLASS(2) t 0V -4V -9.3V -18V -48V VOUT Figure 2. Detection, 2-Event Classification, and Port Power-Up Sequence 16 ������������������������������������������������������������������������������������� Single-Port, 40W, IEEE 802.3af/802.3at PSE Controller with Integrated MOSFET the tFAULT limit, the MAX5971A powers down the port. For a continuous overstress, a fault occurs exactly after a period of tFAULT. After a power-off due to an overcurrent fault, the tFAULT timer is not immediately reset but starts decrementing. The MAX5971A allows the port to be powered on only when the tFAULT counter reaches zero. This feature sets an automatic port power duty-cycle protection to the internal MOSFET to avoid overheating. In the normal powered state, the ILIM and ICUT thresholds are set automatically according to the classification result (see Table 2 for classification results based on detection current, and the Electrical Characteristics table for the corresponding thresholds). During startup, ILIM is always set to 420mA regardless of the detected class. In the normal powered state, the MAX5971A checks for overcurrent conditions, as determined by ICUT = ~88% of ILIM. The tFAULT counter sets the maximum allowed continuous overcurrent period. This timer is incremented both in startup and in normal powered state, but under different conditions. During startup, the counter increases when IRSENSE exceeds ILIM, while in the normal powered state the counter increases when IRSENSE exceeds ICUT. It decreases at a slower pace when IRSENSE drops below ILIM or ICUT. A slower decrement for the tFAULT counter allows for detection of repeated shortduration overcurrent events. When the counter reaches Foldback Current During startup and normal operation, an internal circuit senses the port voltage and reduces the current-limit value and the overcurrent threshold when (VAGND VOUT) < 27V. The foldback function helps to reduce the power dissipation on the internal MOSFET. The current limit eventually reduces down to ITH_FB when (VAGND VOUT) < 10V (see Figure 3). IRSENSE ILIM ITH_FB 10V 27V VAGND - VOUT Figure 3. Foldback Current Characteristics ______________________________________________________________________________________ 17 MAX5971A Overcurrent Protection The MAX5971A has an internal sense resistor, RSENSE (see the Simplified Diagram), connected between the source of the internal MOSFET and VEE to monitor the load current. Under normal operating conditions, the current through RSENSE (IRSENSE) never exceeds the threshold ILIM. If IRSENSE exceeds ILIM, an internal current-limiting circuit regulates the gate voltage of the internal MOSFET, limiting the current. During transient conditions, if IRSENSE exceeds ILIM by more than 2A, a fast pulldown circuit activates to quickly recover from the current overshoot. MAX5971A Single-Port, 40W, IEEE 802.3af/802.3at PSE Controller with Integrated MOSFET Digital Logic a blocking diode in series to OUT and an RC circuit in parallel to the DET diode must be used, as shown in the typical operating circuit of Figure 7. The MAX5971A internally generates digital supplies (referenced to VEE) to power the internal logic circuitry. All logic inputs and outputs are referenced to VEE. See the Electrical Characteristics table for digital input thresholds. If digital logic inputs are driven externally, the nominal digital logic level is 3.3V. The AC disconnect uses an internal triangle wave generator to supply the probing signal. Then the resulting 4VP-P amplitude wave is forced on DET. The common mode of the output signal probed on DET is 5V below AGND. If the AC current peak into DET falls below IACTH for more than tDISC, the device powers down the port. Undervoltage and Overvoltage Protection The MAX5971A contains undervoltage and overvoltage protection features. An internal VEE undervoltage lockout (VEE_UVLO) circuit keeps the port off and the MAX5971A in reset until VAGND - VEE exceeds 28.5V (typ) for more than 2.5ms. An internal VEE overvoltage (VEE_OV) circuit shuts down the port when (VAGND - VEE) exceeds 62.5V (typ). PWM and LED Signals The MAX5971A includes a multifunction LED driver to inform the user of the port status. LED is an open-drain, multifunction output referenced to VEE and can sink up to 10mA (typ) while driving an external LED. The LED is turned on when the port is connected to a valid PD and powered. If the port is not powered or is disconnected, the LED will be off. DC Disconnect Monitoring Force OSC to VEE and power or reset the device to activate DC load-disconnect monitoring. If IRSENSE (the current across RSENSE) falls below the DC load-disconnect threshold, IDCTH, for more than tDISC, the device turns off port power. For two other conditions, the MAX5971A blinks a code to communicate the port status. A series of two flashes indicates an overcurrent fault occurred during port power-on, and has a timing characteristic detailed by Figure 4. A series of five flashes indicates that during detection an invalid low or high discovery signature resistance was detected and has a timing characteristic detailed by Figure 5. AC Disconnect Monitoring The MAX5971A features AC load-disconnect monitoring. Bypass OSC with a 100nF (Q10% tolerance) external capacitor to VEE and power or reset the device to enable AC disconnect. When AC disconnect is enabled, PORT POWERED ON LED ON PORT POWERED DOWN, DUE TO OVERCURRENT FAULT LED OFF LED ON LED OFF LED ON 223ms 74ms 223ms 74ms PORT POWERED ON AGAIN LED OFF LED ON Figure 4. LED Code Timing for Overcurrent Fault During Port Power-On INVALID HIGH OR LOW DISCOVERY SIGNATURE RESISTANCE DETECTED LED ON LED OFF LED ON LED OFF LED ON LED OFF LED ON LED OFF LED ON 74ms 223ms 74ms 223ms 74ms 223ms 74ms 223ms 74ms LED OFF 1.4s SEQUENCE REPEATS Figure 5. LED Code Timing for Detection Fault Due to High- or Low-Discovery Signature Resistance 18 ������������������������������������������������������������������������������������� Single-Port, 40W, IEEE 802.3af/802.3at PSE Controller with Integrated MOSFET 1) Place the input bypass capacitance and the output bypass capacitor (0.1µF ceramic capacitor from AGND to OUTP) as close to the MAX5971A as possible. 2) Use large SMT component pads for power dissipating devices such as the MAX5971A and the external diodes in the high-power path. 3) Use short, wide traces whenever possible for highpower paths. 4) Use the MAX5971 Evaluation Kit as a design and layout reference. 5) The exposed pad (EP) must be soldered evenly to the PCB ground plane for proper operation and power dissipation. Use multiple vias beneath the exposed paddle for maximum heat dissipation. A 1.0mm to 1.2mm pitch is the recommended spacing for these vias and they should be plated (1oz copper) with a small barrel diameter (0.30mm to 0.33mm). Thermal Shutdown If the MAX5971A die temperature reaches 150NC, an overtemperature fault is generated and the device shuts down. The die temperature must cool down below 130NC to remove the overtemperature fault condition. After a thermal shutdown condition clears, the device is reset. Applications Information Layout Procedure Careful PCB layout is critical to achieve high efficiency and low EMI. Follow these layout guidelines for optimal performance. 1N4448 SMJ58A 10mH 0.1µF 100V 2.2MI PSE OUTPUT 47µF 100V 0.1µF 100V LED 5.1kI AGND OUT LED EN MAX5971A OUTP 1nF -54V VEE 1N4448 VEE_DIG DET LEGACY ILIM1 MIDSPAN ILIM2 1kI -54V 1kI OSC PWMEN Figure 6. Typical Operating Circuit 1 (DC Load Removal Detection, Internal PWM Enabled for LED Indication, and Class 5 Detection Enabled) ______________________________________________________________________________________ 19 MAX5971A The MAX5971A also contains an internal square wave, PWM signal generator. The PWM runs at a typical frequency of 25kHz with an approximate typical duty cycle of 6.25%. PWMEN is used to enable or disable the PWM. PWMEN is internally pulled up to the digital supply, and can be left unconnected to enable the internal PWM. When enabled, the LED pulses are driven by the PWM to reduce the power dissipation and increase the system efficiency. Force PWMEN low to disable the internal PWM; the LED is then driven directly. MAX5971A Single-Port, 40W, IEEE 802.3af/802.3at PSE Controller with Integrated MOSFET 1N4448 SMJ58A 10mH 0.1µF 100V 2.2MI PSE OUTPUT 47µF 100V 0.1µF 100V LED 5.1kI AGND LED OUT EN OUTP S1B MAX5971A 1nF VEE -54V 1N4448 0.47FF 100V 1kI VEE_DIG DET LEGACY ILIM1 MIDSPAN ILIM2 1kI -54V 1kI PWMEN OSC 0.1µF Figure 7. Typical Operating Circuit 2 (AC Load Removal Detection, Internal PWM Enabled for LED Indication, and Class 5 Detection Enabled) 47µF 100V 0.1µF 100V SMJ58A 0.1µF 100V 2.2MI PSE OUTPUT AGND VEE -54V OUT VEE_DIG EN OUTP MAX5971A 1N4448 1nF LED PWMEN DET LEGACY ILIM1 MIDSPAN ILIM2 OSC Figure 8. Typical Operating Circuit 3 (IEEE 802.3at Compliant, Minimal Application Circuit with DC Load Removal Detection and No LED Indication) 20 ������������������������������������������������������������������������������������� Single-Port, 40W, IEEE 802.3af/802.3at PSE Controller with Integrated MOSFET Process: BiCMOS Package Information For the latest package outline information and land patterns, go to www.maxim-ic.com/packages. Note that a “+”, “#”, or “-” in the package code indicates RoHS status only. Package drawings may show a different suffix character, but the drawing pertains to the package regardless of RoHS status. PACKAGE TYPE PACKAGE CODE DOCUMENT NO. 28 TQFN-EP T2855+6 21-0140 Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are implied. Maxim reserves the right to change the circuitry and specifications without notice at any time. Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 © 2010 Maxim Integrated Products 21 Maxim is a registered trademark of Maxim Integrated Products, Inc. MAX5971A Chip Information