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_______________________________________________________________ maxim integrated products 1 for pricing, delivery, and ordering information, please contact maxim direct at 1-888-629-4642, or visit maxims website at www.maxim-ic.com. 19-6142; rev 0; 12/11 typical operating circuit general description the MAX5984 is a single-port, power-sourcing equip - ment (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 MAX5984 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 MAX5984 provides up to 40w to a single port (class 5 enabled) and still provides high- capacitance detection for legacy pds. the MAX5984 provides input undervoltage lockout (uvlo), input overvoltage lockout, overtemperature detection, output voltage slew-rate limit during startup, and led status indication. the MAX5984 is available in a space-saving, 28-pin tqfn (5mm x 5mm) power package, and is rated for the extended (-40 n c to +85 n c) temperature range. applications single-port pse end-point applications single-port pse power injectors (midspan applications) poe repeaters switches/routers industrial automation equipment wireless lan access point/wimax ? base stations features s ieee 802.3af/at compliant s up to 40w for single-port pse applications s integrated 0.5 i power mosfet and sense resistor s 2-event pin-select (MAX5984a/MAX5984b) 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 + denotes a lead(pb)-free/rohs-compliant package. *ep = exposed pad. **future productcontact factory for availability. ordering information ieee is a registered service mark of the institute of electrical and electronics engineers, inc. wimax is a registered service mark of wimax forum corp. evaluation kit available -54v agnd led 2-event v ee_dig v ee legacy midspan osc en out outp det ilim1 ilim2 MAX5984a pse output part pin- select temp range pin- package MAX5984aeti+ 2-event -40 n c to +85 n c 28 tqfn-ep* MAX5984beti+** 2-event -40 n c to +85 n c 28 tqfn-ep* MAX5984ceti+** pwmen -40 n c to +85 n c 28 tqfn-ep* MAX5984deti+ lscen -40 n c to +85 n c 28 tqfn-ep* MAX5984 single-port, 40w, ieee 802.3af/at pse controller with integrated mosfet
2 ______________________________________________________________________________________ stresses beyond those listed under absolute maximum ratings may cause permanent damage to the device. these are stress rating s only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specificatio ns is not implied. exposure to absolute maximum rating conditions for extended periods may affect device reliability. (voltages referenced to v ee , unless otherwise noted.) agnd, det, led .................................................. -0.3v to +80v out ...................................................... -0.3v to ( v agnd + 0.3v) outp ....................................................... -6v to ( v agnd + 0.3v) v ee_dig ............................................................... -0.3v to +0.3v osc ......................................................................... -0.3v to +6v en, 2-event/pwmen/lscen, midspan, legacy, ilim1, ilim2..........................................-0.3v to +4v maximum current into led ................................................ 40ma maximum current into out ......................... internally regulated continuous power dissipation (t a = +70 n c) tqfn (derate 34.5mw/ n c above +70 n c) ............... 2758.6mw operating temperature range .......................... -40 n c to +85 n c storage temperature range ............................ -65 n c to +150 n c junction temperature ..................................................... +150 n c lead temperature (soldering, 10s) ................................ +300 n c soldering temperature (reflow) ...................................... +260 n c electrical characteristics (v agnd - v ee = 32v to 60v, t a = -40 n c to +85 n c, all voltages are referenced to v ee , unless otherwise noted. typical values are at v agnd - v ee = 54v, t a = +25 n c. currents are positive when entering the pin and negative otherwise.) (note 2) absolute maximum ratings note 1: package thermal resistances were obtained using the method described in jedec specification jesd51-7, using a four- layer board. for detailed information on package thermal considerations, refer to www.maxim-ic.com/thermal-tutorial . package thermal characteristics (note 1) tqfn junction-to-ambient thermal resistance ....................... 29 n c junction-to-case thermal resistance .............................. 2 n c parameter symbol conditions min typ max units power supplies operating voltage range v agnd v agnd - v ee 32 60 v supply current i ee v out = v ee , all logic inputs unconnected, measured at agnd in power mode 2.5 4 ma current limit current limit i lim maximum i load allowed during current-limit conditions, v out = 0v (note 3) class 0, 1, 2, 3 400 420 441 ma class 4 684 720 756 class 5 if ilim1 = v ee , ilim2 = unconnected 807 850 893 class 5 if ilim1 = unconnected, ilim2 = v ee 855 900 945 class 5 if ilim1 = v ee , ilim2 = v ee 902 950 998 foldback initial out voltage v flbk_st v agnd - v out below which the current limit starts folding back 27 v foldback final out voltage v flbk_end v agnd - v out below which the current limit reaches i th_fb 10 v minimum foldback current limit threshold i th_fb v out = v agnd 166 ma MAX5984 single-port, 40w, ieee 802.3af/802.3at pse controller with integrated mosfet
_______________________________________________________________________________________ 3 electrical characteristics (continued) (v agnd - v ee = 32v to 60v, t a = -40 n c to +85 n c, all voltages are referenced to v ee , unless otherwise noted. typical values are at v agnd - v ee = 54v, t a = +25 n c. currents are positive when entering the pin and negative otherwise.) (note 2) parameter symbol conditions min typ max units overcurrent overcurrent threshold i cut overcurrent threshold allowed for t p t fault , v out = 0v (note 3) class 0, 1, 2, 3 351 370 389 ma class 4 602 634 666 class 5 if ilim1 = v ee , ilim2 = unconnected 710 748 785 class 5 if ilim1 = unconnected, ilim2 = v ee 752 792 832 class 5 if ilim1 = v ee , ilim2 = v ee 794 836 878 internal power dmos on-resistance r ds(on) measured from out to v ee , i out = 100ma t a = +25 n c 0.5 0.9 i t a = +85 n c 0.6 1.3 power-off out leakage current i out_leak v en = v ee , v out = v agnd 10 f a supply monitors v ee undervoltage lockout v ee_uvlo v agnd - v ee , v agnd increasing 28.5 v v ee undervoltage lockout hysteresis v ee_uvloh port is shutdown if: v agnd - v ee < v ee_ uvlo - v ee_uvloh 3 v v ee overvoltage lockout v ee_ov v agnd - v ee > v ee_ov , v agnd increasing 62.5 v v ee overvoltage lockout hysteresis v ee_ovh 1 v thermal shutdown threshold t shd port is shutdown and device resets if the junction temperature exceeds this limit, temperature increasing +150 n c thermal shutdown hysteresis t shdh temperature decreasing 20 n c output monitor out input current i bout v out = v agnd , probing phases 6 f a idle pullup current at out i dis outp discharge current, detection and classification off, port shutdown, v outp = v agnd - 2.8v 200 265 f a short to v ee detection threshold dcn th v out - v ee, v out decreasing, enabled during detection 1.5 2.0 2.5 v short to v ee detection threshold hysteresis dcn hy 220 mv load disconnect dc load-disconnect threshold i dcth minimum load current allowed before disconnect (dc disconnect active), v out = 0v 5 7.5 10 ma ac load-disconnect threshold i acth current into det, for i det < i acth the port powers off (ac disconnect active) 115 130 145 f a MAX5984 single-port, 40w, ieee 802.3af/802.3at pse controller with integrated mosfet
4 ______________________________________________________________________________________ electrical characteristics (continued) (v agnd - v ee = 32v to 60v, t a = -40 n c to +85 n c, all voltages are referenced to v ee , unless otherwise noted. typical values are at v agnd - v ee = 54v, t a = +25 n c. currents are positive when entering the pin and negative otherwise.) (note 2) parameter symbol conditions min typ max units triangular wave peak-to-peak voltage amplitude amp trw measured at det, referred to agnd 3.85 4 4.2 v osc pullup/pulldown currents i osc measured at osc 26 32 39 f a acd_en threshold v acd_en v osc - v ee > v acd_en to activate ac disconnect 270 330 380 mv load disconnect timer t disc time from i rsense < i dcth (dc disconnect active) or i det < i acth (ac disconnect active) to gate shutdown 300 400 ms detection detection probe voltage (first phase) v dph1 v agnd - v det during the first detection phase 3.8 4 4.2 v detection probe voltage (second phase) v dph2 v agnd - v det during the second detection phase 9 9.3 9.6 v current-limit protection i dlim v det = v agnd during detection, measure current through det 1.50 1.75 2.00 ma short-circuit threshold v dcp if v agnd - v out < v dcp after the first detection phase, a short circuit to agnd is detected 1 v open-circuit threshold i d_open first point measurement current threshold for open condition 8 f a resistor detection window r dok (note 4) 19 26.5 k i resistor rejection window r dbad detection rejects lower values 15.5 k i detection rejects higher values 32 classification classification probe voltage v cl v agnd - v det during classification 16 20 v current-limit protection i cllim v det = v agnd , during classification measure current through det 65 80 ma classification current thresholds i cl classification current thresholds between classes class 0, class 1 5.5 6.5 7.5 ma 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 mark event voltage v mark v agnd - v det during mark event 8 10 v mark event current limit i mark_lim v det = v agnd , during mark event measure current through det 55 80 ma MAX5984 single-port, 40w, ieee 802.3af/802.3at pse controller with integrated mosfet
_______________________________________________________________________________________ 5 note 2: this device is production tested at t a = +25 n c. limits at t a = -40 n c and t a = +85 n c 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: r dok = (v out2 - v out1 )/(i det2 - i det1 ). v out1 , v out2 , i det2 , and i det1 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. electrical characteristics (continued) (v agnd - v ee = 32v to 60v, t a = -40 n c to +85 n c, all voltages are referenced to v ee , unless otherwise noted. typical values are at v agnd - v ee = 54v, t a = +25 n c. currents are positive when entering the pin and negative otherwise.) (note 2) parameter symbol conditions min typ max units digital inputs/outputs (voltages referenced to v ee ) digital input low v il 0.8 v digital input high v ih 2.4 v internal input pullup current i pu pullup current to internal digital supply to set default values 3 5 7 f a led output low voltage v led_low i led = 10ma, pwm disabled, port power-on 0.8 v led output leakage i led_leak pwm disabled, shutdown mode, v led = 60v 10 f a pwm frequency 25 khz pwm duty cycle 6.25 % timing startup time t start time during which a current limit set to 420ma is allowed, starts when power is turned on 50 60 70 ms fault time t fault maximum allowed time for an overcurrent condition set by i cut after startup 50 60 70 ms detection reset time t me time allowed for the port voltage to reset before detection starts 80 90 ms detection time t det maximum time allowed before detection is completed 330 ms midspan mode detection delay t dmid 2 2.2 2.4 s classification time t class time allowed for classification 19 23 ms mark event time time allowed for mark event 7 9 11 ms v eeuvlo turn-on delay t dly time v agnd must be above the v eeuvlo thresholds before the device operates 5.2 ms restart timer t restart time the device waits before turning on after an overcurrent fault 16 x t fault ms MAX5984 single-port, 40w, ieee 802.3af/802.3at pse controller with integrated mosfet
6 ______________________________________________________________________________________ typical operating characteristics (t a = +25c, unless otherwise noted.) dc disconnect threshold vs. temperature MAX5984 toc07 temperature (c) dc disconnect threshold (ma) 60 35 10 -15 6.6 6.8 7.0 7.2 7.4 6.4 -40 85 foldback current-limit threshold vs. output voltage MAX5984 toc06 v agnd - v out (v) i rsense (ma) 30 20 10 100 200 300 400 500 600 700 800 0 0 40 class 4 class 0, 1, 2, 3 internal fet resistance vs. temperature MAX5984 toc05 temperature (c) fet resistance (m?) 60 35 10 -15 400 600 800 1000 200 -40 85 v ee overvoltage lockout vs. temperature MAX5984 toc04 temperature (c) overvoltage lockout (v) 60 35 -15 10 60.5 61.0 61.5 62.0 63.0 62.5 63.5 64.0 60.0 -40 85 v ee undervoltage lockout vs. temperature MAX5984 toc03 temperature (c) undervoltage lockout (v) 60 35 10 -15 27.5 28.0 28.5 29.0 29.5 30.0 27.0 -40 85 analog supply current vs. temperature MAX5984 toc02 temperature (c) supply current (ma) 60 35 10 -15 2.4 2.5 2.6 2.7 2.3 -40 85 measured at agnd analog supply current vs. input voltage MAX5984 toc01 v agnd - v ee (v) supply current (ma) 56 52 48 44 40 36 2.4 2.5 2.6 2.7 2.3 32 60 measured at agnd MAX5984 single-port, 40w, ieee 802.3af/802.3at pse controller with integrated mosfet
_______________________________________________________________________________________ 7 typical operating characteristics (continued) (t a = +25c, unless otherwise noted.) zero-current detection waveform with ac disconnect enabled MAX5984 toc13 40ms/div 0v 0ma v agnd - v out 20v/div i out 100ma/div zero-current detection waveform with dc disconnect enabled MAX5984 toc12 40ms/div 0v 0ma v agnd - v out 20v/div i out 100ma/div en to out turn-off delay MAX5984 toc11 100s/div 0v 0v 0ma v agnd - v out 20v/div i out 200ma/div v en 5v/div short-circuit transient response MAX5984 toc10 10s/div 0v 0ma v agnd - v out 20v/div i out 5a/div short-circuit response time MAX5984 toc09 20ms/div 0v 0ma v agnd - v out 20v/div i out 200ma/div overcurrent timeout (240? to 138? ) MAX5984 toc08 20ms/div 0v 0ma v agnd - v out 20v/div i out 200ma/div MAX5984 single-port, 40w, ieee 802.3af/802.3at pse controller with integrated mosfet
8 ______________________________________________________________________________________ typical operating characteristics (continued) (t a = +25c, unless otherwise noted.) detection with invalid pd (open circuit) MAX5984 toc16d 100ms/div 0v 0ma v agnd - v out 5v/div i out 1ma/div detection with invalid pd (33k? ) MAX5984 toc16c 100ms/div 0v 0ma v agnd - v out 5v/div i out 1ma/div detection with invalid pd (15k? ) MAX5984 toc16b 100ms/div 0v 0ma v agnd - v out 5v/div i out 1ma/div detection with invalid pd (25k? to 10f) MAX5984 toc16a 40ms/div 0v 0ma v agnd - v out 1v/div i out 1ma/div startup with a valid pd MAX5984 toc15 100ms/div 0v 0ma v agnd - v out 20v/div i out 100ma/div overcurrent restart delay MAX5984 toc14 400ms/div 0v 0ma v agnd - v out 20v/div i out 200ma/div MAX5984 single-port, 40w, ieee 802.3af/802.3at pse controller with integrated mosfet
_______________________________________________________________________________________ 9 typical operating characteristics (continued) (t a = +25c, unless otherwise noted.) classification with different pd classes (4 and 5) MAX5984 toc20b 40ms/div 0v 0ma v agnd - v out 10v/div i out 20ma/div class 5 class 4 classification with different pd classes (0 to 3) MAX5984 toc20a 40ms/div 0v 0ma v agnd - v out 10v/div i out 10ma/div class 3 class 2 class 1 class 0 detection in output shorted to agnd MAX5984 toc19 40ms/div 0v 0ma v agnd - v out 5v/div i out 1ma/div detection in midspan with invalid pd (33k? ) MAX5984 toc18b 400ms/div 0v 0ma v agnd - v out 5v/div i out 1ma/div detection in midspan with invalid pd (15k? ) MAX5984 toc18a 400ms/div 0v 0ma v agnd - v out 5v/div i out 1ma/div startup in midspan with a valid pd MAX5984 toc17 100ms/div 0v 0ma v agnd - v out 20v/div i out 100ma/div MAX5984 single-port, 40w, ieee 802.3af/802.3at pse controller with integrated mosfet
10 _____________________________________________________________________________________ typical operating characteristics (continued) (t a = +25c, unless otherwise noted.) led pwm timing and duty cycle MAX5984 toc24 10s/div 0v 0v 0ma v agnd - v out 50v/div v agnd - v led 20v/div i out 500ma/div led overcurrent fault with pwm disabled MAX5984 toc23b 200ms/div 0v 0v 0ma v agnd - v out 50v/div v agnd - v led 20v/div i out 500ma/div led overcurrent fault with pwm enabled MAX5984 toc23a 200ms/div 0v 0v 0ma v agnd - v out 50v/div v agnd - v led 20v/div i out 500ma/div led detection fault with pwm disabled MAX5984 toc22b 200ms/div 0v 0v 0ma v agnd - v out 10v/div v agnd - v led 20v/div i out 500ma/div led detection fault with pwm enabled MAX5984 toc22a 200ms/div 0v 0v 0ma v agnd - v out 10v/div v agnd - v led 20v/div i out 500ma/div startup using 2-event classification with a valid pd MAX5984 toc21 100ms/div 0v 0ma v agnd - v out 20v/div i out 100ma/div MAX5984 single-port, 40w, ieee 802.3af/802.3at pse controller with integrated mosfet
______________________________________________________________________________________ 11 pin description pin configuration 26 27 25 24 10 9 11 v ee ilim1 ilim2 2-event/pwmen/lscen midspan 12 v ee n.c. n.c. led agnd n.c. i.c. 12 outp 45 67 20 21 19 17 16 15 out out v ee_dig i.c. i.c. i.c. MAX5984 v ee osc 3 18 28 8 n.c. i.c. n.c. 23 13 legacy det 22 14 en *exposed pad, connect to agnd. *ep n.c. thin qfn top view + pin name function 1, 2, 3 v ee analog low-side supply input. bypass with an external 100v, 47 f f capacitor in parallel with a 100v, 0.1 f f ceramic capacitance between agnd and v ee . 4 ilim1 class 5 current-limit digital adjust 1. referenced to v ee . 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 for details. 5 ilim2 class 5 current-limit digital adjust 2. referenced to v ee . 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 for details. 6 2-event (MAX5984a/ MAX5984b) 2-event classification select. referenced to v ee . 2-event is internally pulled up to the digital supply. leave unconnected to disable 2-event classification. force low to enable the 2-event classification. see the 2-event pd classification section for more details. change status of this bit only when the part is in reset state. the MAX5984c/MAX5984d are enabled. pwmen (MAX5984c) pwm control logic input. referenced to v ee . 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. the MAX5984a/mac5984b/MAX5984d are enabled. lscen (MAX5984d) load stability check function select. referenced to v ee. lscen is internally pulled up to the digital supply. leave unconnected to enable the load stability check function. force low to disable the load stability check function. change status of this bit only when the part is in reset state. the MAX5984a is disabled but the MAX5984b/MAX5984c are enabled. MAX5984 single-port, 40w, ieee 802.3af/802.3at pse controller with integrated mosfet
12 _____________________________________________________________________________________ pin description (continued) pin name function 7 midspan detection collision avoidance logic input. referenced to v ee . 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. 8C11, 15 i.c. internally connected. connect i.c. to v ee . 12 v ee_dig digital low-side supply input. connect to v ee externally. 13 legacy legacy detection logic input. referenced to v ee . 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 v ee . en is internally pulled up to the digital supply. leave unconnected to enable the device. force low for at least 40 f s 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. 17 led led indicator open-drain output. referenced to v ee . 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 or to an external supply (if available) through a series resistance (figures 6 and 7). 19 osc ac disconnect triangular wave output. bypass with a 100nf ( q 10% tolerance) external capacitor to v ee to enable the ac disconnect function. connect osc to v ee 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 high-side supply input 23 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 1k i and 0.47 f f rc series in parallel with the external protection diode to outp (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 (figures 6 and 8). bypass outp to agnd with a 100v, 0.1 f f ceramic capacitor. 26, 27 out integrated mosfet output. if dc disconnect is used, connect the port output to outp (figures 6 and 8). if the ac disconnect function is used, connect out to the cathode of the ac-blocking diode (figure 7). ep exposed pad. connect ep to v ee externally. see the layout procedure section for details. MAX5984 single-port, 40w, ieee 802.3af/802.3at pse controller with integrated mosfet
______________________________________________________________________________________ 13 simplified diagram detailed description the MAX5984 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 detec - tions. the MAX5984 operates automatically without the need for any software programming and features an inte - grated 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 MAX5984 provides up to 40w to a single port (class 5 enabled) and still provides high-capacitance detection for legacy pds. the MAX5984 provides input uvlo, input overvoltage lockout, overtemperature detection, output voltage slew- rate limit during startup, and led status indication. reset the MAX5984 is reset by any of the following conditions: 1) power-up. reset condition is cleared once v ee rises above the uvlo threshold. 2) hardware reset. reset occurs once the en input is driven low (> 40s 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 shut - down at +150 n c. the device exits thermal shutdown and is reset once the temperature drops below 130 n c. osc status monitor osc legacy en midspan port state machine (sm) register file analog bias and supply monitor voltage probing and current-limit control detection and classification control central logic unit (clu) ac detector 2-event/pwmen/lscen ac disconnect signal (acd) threshold settings acd reference current internal mosfet internal r sense voltage sensing gate drive current limit, overcurrent, and open- circuit sensing, and foldback control class 5 enable/disable, overcurrent and current limit control ilim1 2-event/pwmen/lscen led v ee agnd ilim2 9-bit adc agnd outp out foldback control det triangle wave generator ac disconnect enable a = 1 voltage references current references internal supplies current sensing MAX5984 MAX5984 single-port, 40w, ieee 802.3af/802.3at pse controller with integrated mosfet
14 _____________________________________________________________________________________ during a reset, the MAX5984 latches in the state of midspan, legacy, and osc. during normal operation, changes to these inputs are ignored. 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. automatic operation the MAX5984 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 con - nected at the port, the MAX5984 repeats the detection routine continuously until a valid pd is connected. pd detection during normal operation, the MAX5984 probes the output for a valid pd. a valid pd has a 25k i 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. during detection, the MAX5984 keeps the internal mosfet off and forces two probe voltages through det. the current through det is measured as well as the volt - age 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. 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 MAX5984 limits the current into det to less than 2ma maximum during pd detection. in midspan mode, the MAX5984 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. high-capacitance detection the status of the legacy input is latched during power- up 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 v ee to disable this function. if high- capacitance detection is enabled, pd signature capaci - tances up to 47 f f (typ) are accepted. table 1. pse pd detection modes electrical requirements (ieee 802.3at) parameter symbol min max units additional information open-circuit voltage v oc 30 v in detection mode only short-circuit current i sc 5 ma in detection mode only valid test voltage v valid 2.8 10 v voltage difference between test points d v test 1 v time between any two test points t bp 2 ms this timing implies a 500hz maximum probing frequency slew rate v slew 0.1 v/ f s accept signature resistance r good 19 26.5 k i reject signature resistance r bad < 15 > 33 k i open-circuit resistance r open 500 k i accept signature capacitance c good 150 nf reject signature capacitance c bad 10 f f signature offset voltage tolerance v os 0 2.0 v signature offset current tolerance i os 0 12 f a MAX5984 single-port, 40w, ieee 802.3af/802.3at pse controller with integrated mosfet
______________________________________________________________________________________ 15 pd classification during the pd classification mode, the MAX5984 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 MAX5984 classifies the pd based on table 33.9 of the ieee 802.3at standard (table 2). if the measured current exceeds 51ma, the MAX5984 does not power the pd, but returns to the idle state before attempting a new detection cycle. class 5 pd classification the MAX5984 supports high power beyond the ieee 802.3at standard by providing an additional classifica - tion (class 5) if needed. to enable class 5 detection and select the corresponding current-limit/overcurrent thresholds, ilim1 and ilim2 must be set based on the combinations detailed in table 3. once class 5 is enabled, during classification, if the MAX5984 detects currents in excess of the class 4 upper limit threshold, the pd is classified as a class 5 pd. the pd is guar - anteed 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 v ee 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 v ee (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 MAX5984 per - forms a first and second mark event as required by the ieee 802.3at standard, forcing a -9.0v probing voltage at det. the 2-event function is disabled by default in the MAX5984a/MAX5984b/MAX5984e. however, it is not pin-selectable in the MAX5984e. powered state when the MAX5984 enters a powered state, the t fault and t disc timers are reset. when the startup timer has timed out, the device enters a normal powered condition, allowing power delivery to the pd. table 2. pse classification of a pd (table 33.9 of the ieee 802.3at standard) table 3. class 5 overcurrent threshold and current-limit settings measured i class (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 ilim1 configuration ilim2 configuration overcurrent threshold (ma) current limit (ma) unconnected unconnected class 5 disabled class 5 disabled v ee unconnected 748 850 unconnected v ee 792 900 v ee v ee 836 950 MAX5984 single-port, 40w, ieee 802.3af/802.3at pse controller with integrated mosfet
16 _____________________________________________________________________________________ figure 1. detection, classification, and port power-up sequence figure 2. detection, 2-event classification, and port power-up sequence v out t 0v -4v -9.3v -18v -48v t det(1) t det(2) t class 80ms 150ms 150ms 19ms v out t 0v -4v -9.3v -18v -48v t det(1) t det(2) t class(1) t class(2) 80ms 150ms 150ms 19ms 19ms 9ms 9ms MAX5984 single-port, 40w, ieee 802.3af/802.3at pse controller with integrated mosfet
______________________________________________________________________________________ 17 overcurrent protection the MAX5984 has an internal sense resistor, r sense (see the simplified diagram ), connected between the source of the internal mosfet and v ee to monitor the load current. under normal operating conditions, the current through r sense (i rsense ) never exceeds the threshold i lim . if i rsense exceeds i lim , an internal current-limiting circuit regulates the gate voltage of the internal mosfet, limiting the current. during transient conditions, if i rsense exceeds i lim by more than 2a, a fast pulldown circuit activates to quickly recover from the current overshoot. in the normal powered state, the MAX5984 checks for overcurrent conditions, as determined by i cut = ~88% of i lim . the t fault 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 increas - es when i rsense exceeds i lim , while in the normal pow - ered state the counter increases when i rsense exceeds i cut . it decreases at a slower pace when i rsense drops below i lim or i cut . a slower decrement for the t fault counter allows for detection of repeated short- duration overcurrent events. when the counter reaches the t fault limit, the MAX5984 powers down the port. for a continuous overstress, a fault occurs exactly after a period of t fault . after a power-off due to an overcurrent fault, the t fault timer is not immediately reset but starts decrementing. the MAX5984 allows the port to be powered on only when the t fault 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 i lim and i cut thresh - olds 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, i lim is always set to 420ma regardless of the detected class. 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 (v agnd - v out ) < 27v. the foldback function helps to reduce the power dissipation on the internal mosfet. the current limit eventually reduces down to i th_fb when (v agnd - v out ) < 10v (figure 3). figure 3. foldback current characteristics v agnd - v out i lim i th_fb 10v 27v i rsense MAX5984 single-port, 40w, ieee 802.3af/802.3at pse controller with integrated mosfet
18 _____________________________________________________________________________________ digital logic the MAX5984 internally generates digital supplies (ref - erenced to v ee ) to power the internal logic circuitry. all logic inputs and outputs are referenced to v ee . see the electrical characteristics table for digital input thresh - olds. if digital logic inputs are driven externally, the nominal digital logic level is 3.3v. undervoltage and overvoltage protection the MAX5984 contains undervoltage and overvoltage protection features. an internal v ee undervoltage lockout (v ee_uvlo ) circuit keeps the port off and the MAX5984 in reset until v agnd - v ee exceeds 28.5v (typ) for more than 2.5ms. an internal v ee overvoltage (v ee_ov ) circuit shuts down the port when (v agnd - v ee ) exceeds 62.5v (typ). dc disconnect monitoring force osc to v ee and power or reset the device to acti - vate dc load-disconnect monitoring. if i rsense (the cur - rent across r sense ) falls below the dc load-disconnect threshold, i dcth , for more than t disc , the device turns off port power. ac disconnect monitoring the MAX5984 features ac load-disconnect monitoring. bypass osc with a 100nf ( q 10% tolerance) external capacitor to v ee and power or reset the device to enable ac disconnect. when ac disconnect is enabled, a blocking diode in series to out and an rc circuit in parallel to the det diode must be used, as shown in figure 7. the ac disconnect uses an internal triangle wave gen - erator to supply the probing signal. then the resulting 4v p-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 i acth for more than t disc , the device powers down the port. pwm and led signals the MAX5984 includes a multifunction led driver to inform the user of the port status. led is an open-drain, multifunction output referenced to v ee 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. for two other conditions, the MAX5984 blinks a code to communicate the port status. a series of two flashes indi - cates 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. figure 4. led code timing for overcurrent fault during port power-on figure 5. led code timing for detection fault due to high- or low-discovery signature resistance led of f led on 223m s led on led on led on led of fl ed of f 74ms 74m s 223m s port powered down, due to overcurrent faul t port powered on port powered on agai n led off led on 223ms 74ms led off led on 223ms 74ms led off led on 223ms 74ms led off led on 223ms 74ms led on 74ms led off 1.4s sequence repeats invalid high or low discovery signature resistance detected MAX5984 single-port, 40w, ieee 802.3af/802.3at pse controller with integrated mosfet
______________________________________________________________________________________ 19 the MAX5984 also contains an internal square wave, pwm signal generator. the pwm runs at a typical fre - quency 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. thermal shutdown if the MAX5984 die temperature reaches +150 n c, an overtemperature fault is generated and the device shuts down. the die temperature must cool down below 130 n c 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. 1) place the input bypass capacitance and the output bypass capacitor (0.1f ceramic capacitor from agnd to outp) as close as possible to the MAX5984. 2) use large smt component pads for power dissipat - ing devices such as the MAX5984 and the external diodes in the high-power path. 3) use short, wide traces whenever possible for high- power 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 pad 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). figure 6. typical operating circuit 1 (dc load removal detection, internal pwm enabled for led indication, and class 5 detection enabled) 1n4448 1ki 1ki 1nf -54v 5.1ki led 10mh 1n4448 0.1f 100v 47f 100v -54v led agnd en v ee v ee_dig legacy midspan osc out outp det ilim1 ilim2 pwmen MAX5984c 0.1f 100v smj58a 2.2mi pse output MAX5984 single-port, 40w, ieee 802.3af/802.3at pse controller with integrated mosfet
20 _____________________________________________________________________________________ figure 7. typical operating circuit 2 (ac load removal detection, internal pwm enabled for led indication, and class 5 detection enabled) figure 8. typical operating circuit 3 (ieee 802.3at compliant, minimal application circuit with dc load removal detection and no led indication) 1n4448 s1b 1ki 1ki 1ki 1nf 0.1f -54v 5.1ki led 10mh 1n4448 0.1f 100v 47f 100v 0.47ff 100v -54v led agnd en v ee v ee_dig legacy midspan osc out outp det ilim1 ilim2 pwmen MAX5984c 0.1f 100v smj58a 2.2mi pse output 1n4448 1nf -54v agnd en led v ee_dig v ee 2-event/ lscen legacy midspan osc out outp det ilim1 ilim2 MAX5984a/b/d 0.1f 100v smj58a 2.2mi 47f 100v 0.1f 100v pse output MAX5984 single-port, 40w, ieee 802.3af/802.3at pse controller with integrated mosfet
______________________________________________________________________________________ 21 package information for the latest package outline information and land patterns (footprints), 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. chip information process: bicmos package type package code outline no. land pattern no. 28 tqfn-ep t2855+6 21-01 40 90-0026 MAX5984 single-port, 40w, ieee 802.3af/802.3at pse controller with integrated mosfet
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. 22 maxim integrated products, 120 san gabriel drive, sunnyvale, ca 94086 408-737-7600 ? 2011 maxim integrated products maxim is a registered trademark of maxim integrated products, inc. revision history revision number revision date description pages changed 0 12/11 initial release MAX5984 single-port, 40w, ieee 802.3af/802.3at pse controller with integrated mosfet

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