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? semiconductor components industries, llc, 2013 may, 2013 ? rev. 3 1 publication order number: ncp1082/d ncp1082 integrated poe-pd & dc-dc converter controller with 9v auxiliary supply support introduction the ncp1082 is a member of on semiconductor?s power over ethernet powered device (poe ? pd) product family and represents a robust, flexible and highly integrated solution targeting demanding ethernet applications. it combines in a single unit an enhanced poe ? pd interface fully supporting the ieee 802.3af specification and a flexible and configurable dc ? dc converter controller. the ncp1082?s exceptional capabilities enable applications to smoothly transition from non ? poe to poe enabled networks by also supporting power from auxiliary sources such as ac power adapters and battery supplies, eliminating the need for a second switching power supply. on semiconductor?s unique manufacturing process and design enhancements allow the ncp1082 to deliver up to 13 w of regulated power to support poe applications according to the ieee 802.3af standard. this device leverages the significant cost advantages of poe ? enabled systems to a broad spectrum of products in markets such as voip phones, wireless lan access points, security cameras, point of sales terminals, rfid readers, industrial ethernet devices, etc. the integrated current mode dc ? dc controller facilitates isolated and non ? isolated fly ? back, forward and buck converter topologies. it has all the features necessary for a flexible, robust and highly ef ficient design including programmable switching frequency, duty cycle up to 80 percent, slope compensation, and soft start ? up. the ncp1082 is fabricated in a robust high voltage process and integrates a rugged vertical n ? channel dmos with a low loss current sense technique suitable for the most demanding environments and capable of withstanding harsh environments such as hot swap and cable esd events. the ncp1082 complements on semiconductor?s assp portfolio in communications and industrial devices and can be combined with other high ? voltage interfacing devices to offer complete solutions to the communication, industrial and security markets. features ? this is a pb ? free device powered device interface ? flexible auxiliary power supply support ? 9 v front, rear and direct auxiliary supply connections ? fully supports ieee 802.3af standard ? regulated power output up to 13 w ? programmable classification current ? adjustable under voltage lock out ? programmable inrush current limit ? programmable operational current limit up to 500 ma ? over ? temperature protection ? industrial t emperature range ? 40 c to 85 c with full operation up to 150 c junction temperature ? 0.6 ohm hot ? swap pass ? switch with low loss current sense technique ? vertical n ? channel dmos pass ? switch offers the robustness of discrete mosfets with integrated temperature control http://onsemi.com ncp1082 = specific device code xxxx = date code y = assembly location zz = traceability code tssop ? 20 ep de suffix case 948ab see detailed ordering and shipping information in the package dimensions section on page 2 of this data sheet. ordering information 1
ncp1082 http://onsemi.com 2 dc ? dc converter controller ? current mode control ? supports isolated and non ? isolated dc ? dc converter applications ? internal voltage regulators ? wide duty cycle range with internal slope compensation circuitry ? programmable oscillator frequency ? programmable soft ? start time (top view) pin diagram exposed pad 1 ss fb comp vddl vddh gate artn nc cs osc vportp class uvlo inrush ilim1 vportn1 rtn vportn2 aux test ordering information part number temperature range package shipping configuration ? ncp1082deg ? 40 c to 85 c tssop ? 20 ep (pb ? free) 74 units / tube NCP1082DER2G ? 40 c to 85 c tssop ? 20 ep (pb ? free) 2500 / tape & reel ?for information on tape and reel specifications, including part orientation and tape sizes, please refer to our tape and reel packaging specification brochure, brd8011/d. internal supply & bandgap vddh inrush ilim1 classification detection vportn1,2 vportp class inrush ilim1 vddh nc vddl thermal shut down hot swap switch control & current limit blocks uvlo uvlo rtn artn 1.2 v dc ? dc converter control osc ss fb comp cs gate vddl vddl vddl vddh 5 k osc vport monitor vddl figure 1. ncp1082 block diagram 5 a aux detection auxiliary supply
ncp1082 http://onsemi.com 3 simplified application diagrams figure 2. isolated fly ? back converter with rear auxiliary support ncp1082 rcs cvddl cvddh cpd css rosc m1 t1 cload ld1 rd1 rclass rilim1 rinrush optocoupler r3 r4 r5 c1 z1 rslope c2 voutput d1 oc1 gate rtn fb vportn2 vddh vddl vportn1 class artn ilim1 inrush test aux uvlo cs vportp data pairs spare pairs r1 r2 rj ? 45 db1 db2 raux1 vaux(+) vaux( ? ) raux2 raux3 d3 d4 cline z_line comp ss osc figure 2 shows the integrated poe ? pd switch and dc ? dc controller configured to work in a fully isolated application. the output voltage regulation is accomplished with an external opto ? coupler and a shunt regulator (z1). figure 3. non ? isolated fly ? back converter with rear auxiliary support ncp1082 rcs cvddl cvddh cpd css rosc m1 t1 cload ld1 rd1 rclass rilim1 rinrush rslope voutput d1 gate rtn fb vportn2 vddh vddl vportn1 class artn ilim1 inrush test aux uvlo cs vportp data pairs spare pairs r1 r2 rj ? 45 db1 db2 raux1 vaux(+) vaux( ? ) raux2 raux3 d2 d3 cline z_line comp ss osc r3 r4 c1comp c2comp rcomp figure 3 shows the integrated poe ? pd and dc ? dc controller configured in a non ? isolated fly ? back configuration. a compensation network is inserted between the fb and the comp pin for overall stability of the feedback loop.
ncp1082 http://onsemi.com 4 simplified application diagrams figure 4. non ? isolated fly ? back with extra winding and rear auxiliary support ncp1082 rcs cvddl cvddh cpd css rosc m1 t1 cload ld1 rd1 rclass rilim1 rinrush rslope voutput d1 gate rtn fb vportn2 vddh vddl vportn1 class artn ilim1 inrush test aux uvlo cs vportp data pairs spare pairs r1 r2 rj ? 45 db1 db2 raux1 vaux(+) vaux( ? ) raux2 raux3 d3 d4 cline z_line comp ss osc r3 r4 c1comp c2comp rcomp r5 d2 figure 4 shows the same non ? isolated fly ? back configuration as figure 3, but adds a 12 v auxiliary bias winding on the transformer to provide power to the ncp1082 dc ? dc controller via its vddh pin. this topology shuts off the current flowing from vportp to vddh and therefore reduces the internal power dissipation of the pd, resulting in higher overall power efficiency. figure 5. non ? isolated forward converter with rear auxiliary support ncp1082 rcs cvddl cvddh cpd css rosc m1 t1 cload ld1 rd1 rclass rilim1 rinrush rslope voutput d1 gate rtn fb vportn2 vddh vddl vportn1 class artn ilim1 inrush test aux uvlo cs vportp data pairs spare pairs r1 r2 rj ? 45 db1 db2 raux1 vaux(+) vaux( ? ) raux2 raux3 d4 d5 cline z_line comp ss osc r3 r4 c1comp c2comp rcomp d3 d2 l1 figure 5 shows the ncp1082 used in a non ? isolated forward topology.
ncp1082 http://onsemi.com 5 table 1. pin descriptions name pin no. type description vportp 1 supply positive input power. voltage with respect to vportn 1,2 vportn1 vportn2 6,8 ground negative input power. connected to the source of the internal pass ? switch. rtn 7 ground dc ? dc controller power return. connected to the drain of the internal pass ? switch. it must be connected to artn. this pin is also the drain of the internal pass ? switch. artn 14 ground dc ? dc controller ground pin. must be connected to rtn as a single point ground connection for improved noise immunity. vddh 16 supply output of the 9 v ldo internal regulator. voltage with respect to artn. supplies the internal gate driver. vddh must be bypassed to artn with a 1 f or 2.2 f ceramic capacitor with low esr. vddl 17 supply output of the 3.3 v ldo internal regulator. voltage with respect to artn. this pin can be used to bias an external low ? power led (1 ma max.) connected to artn, and can also be used to add extra biasing current in the external opto ? coupler. vddl must be bypassed to artn with a 330 nf or 470 nf ceramic capacitor with low esr. class 2 input classification current programming pin. connect a resistor between class and vportn 1,2 . inrush 4 input inrush current limit programming pin. connect a resistor between inrush and vportn 1,2 . ilim1 5 input operational current limit programming pin. connect a resistor between ilim1 and vportn 1,2 . uvlo 3 input dc ? dc controller under ? voltage lockout input. voltage with respect to vportn 1,2 . connect a resistor ? divider from vportp to uvlo to vportn 1,2 to set an external uvlo threshold. gate 15 output dc ? dc controller gate driver output pin. osc 11 input internal oscillator frequency programming pin. connect a resistor between osc and artn. nc 13 no connect pin, must not be connected. comp 18 i/o output of the internal error amplifier of the dc ? dc controller. comp is pulled ? up internally to vddl with a 5 k resistor. in isolated applications, comp is connected to the collector of the opto ? coupler. voltage with respect to artn. fb 19 input dc ? dc controller inverting input of the internal error amplifier. in isolated applications, the pin should be strapped to artn to disable the internal error amplifier. cs 12 input current ? sense input for the dc ? dc controller. voltage with respect to artn. ss 20 input soft ? start input for the dc ? dc controller. a capacitor between ss and artn determines the soft ? start timing. aux 9 input when the pin is pulled up, the ieee detection mode is disabled and the device can be sup- plied by an auxiliary supply. voltage with respect to vportn 1,2 . connect the pin to the auxili- ary supply through a resistor divider. test 10 input digital test pin must always be connected to vportn 1,2 . ep exposed pad. connected to vportn 1,2 ground.
ncp1082 http://onsemi.com 6 table 2. absolute maximum ratings symbol parameter conditions min max unit vportp input power supply voltage with respect to vportn 1,2 ? 0.3 72 v rtn artn analog ground supply 2 pass ? switch in off ? state (voltage with respect to vportn 1,2 ) ? 0.3 72 v vddh internal regulator output voltage with respect to artn ? 0.3 17 v vddl internal regulator output voltage with respect to artn ? 0.3 3.6 v class analog output voltage with respect to vportn 1,2 ? 0.3 3.6 v inrush analog output voltage with respect to vportn 1,2 ? 0.3 3.6 v ilim1 analog output voltage with respect to vportn 1,2 ? 0.3 3.6 v uvlo analog input voltage with respect to vportn 1,2 ? 0.3 3.6 v osc analog output voltage with respect to artn ? 0.3 3.6 v comp analog input / output voltage with respect to artn ? 0.3 3.6 v fb analog input voltage with respect to artn ? 0.3 3.6 v cs analog input voltage with respect to artn ? 0.3 3.6 v ss analog input voltage with respect to artn ? 0.3 3.6 v nc open pin aux analog input voltage with respect to vportn 1,2 ? 0.3 3.6 v test digital input voltage with respect to vportn 1,2 ? 0.3 3.6 v t a ambient temperature ? 40 85 c t j junction temperature ? 150 c t j ? tsd junction temperature (note 1) thermal shutdown condition ? 175 c t stg storage temperature ? 55 150 c t ja thermal resistance, junction to air (note 2) exposed pad connected to vportn 1,2 ground 37.6 c/w esd ? hbm human body model per jedec standard jesd22 4 ? kv esd ? cdm charged device model 750 ? v esd ? mm machine model 300 ? v lu latch ? up per jedec standard jesd78 200 ? ma esd ? sys system esd (contact/air) (note 3) 8/15 ? kv stresses exceeding maximum ratings may damage the device. maximum ratings are stress ratings only. functional operation above t he recommended operating conditions is not implied. extended exposure to stresses above the recommended operating conditions may af fect device reliability. 1. t j ? tsd allowed during error conditions only. it is assumed that this maximum temperature condition does not occur more than 1 hour cumulative during the useful life for reliability reasons. 2. mounted on a 1s2p (3 layer) test board with copper coverage of 25 percent for the signal layers and 90 percent copper coverag e for the inner planes at an ambient temperature of 85 c in still air. refer to jedec jesd51 ? 7 for details. 3. surges per en61000 ? 4 ? 2, 1999 applied between rj ? 45 and output ground and between adapter input and output ground of the demo board. the specified values are the test levels and not the failure levels.
ncp1082 http://onsemi.com 7 recommended operating conditions operating conditions define the limits for functional operation and parametric characteristics of the device. note that the functionality of the device outside the operating conditions described in this section is not warranted. operating outside the recommended operating conditions for extended periods of time may affect device reliability. all values concerning the dc ? dc controller, vddh and vddl blocks are with respect to artn. all others are with respect to vportn 1,2 (unless otherwise noted). table 3. operating conditions symbol parameter conditions min typ max unit input supply vport input supply voltage vport = vportp ? vportn 1,2 0 57 v signature detection vsignature input supply voltage signature detection range 1.4 9.5 v rsignature signature resistance (note 4) 23.75 26.25 k offset_current i_vportp + i_rtn vportp = rtn = 1.4 v ? 1.8 5 a sleep_current i_vportp + i_rtn vportp = rtn = 9.5 v ? 15 25 a classification vcl input supply voltage classification range 13 20.5 v iclass0 class 0: rclass 10 k (note 5) iclass0 = i_vportp + i_rdet 0 ? 4 ma iclass1 class 1: rclass 130 (note 5) iclass1 = i_vportp + i_rdet 9 ? 12 ma iclass2 class 2: rclass 69.8 (note 5) iclass2 = i_vportp + i_rdet 17 ? 20 ma iclass3 class 3: rclass 44.2 (note 5) iclass3 = i_vportp + i_rdet 26 ? 30 ma iclass4 class 4: rclass 30.9 (note 5) iclass4 = i_vportp + i_rdet 36 ? 44 ma idc class internal current consumption during classification (note 6) for information only ? 600 ? a uvlo vuvlo_on default turn on voltage (vportp rising) uvlo pin tied to vportn 1,2 38 40 v vuvlo_off default turn off voltage (vportp falling) uvlo pin tied to vportn 1,2 29.5 32 ? v vhyst_int uvlo internal hysteresis uvlo pin tied to vportn 1,2 ? 6 ? v vuvlo_pr uvlo external programming range uvlo pin connected to the resistor divider (r1 & r2) aux pin tied to vportn 1,2 for information only 13 ? 50 v vuvlo_pr_aux uvlo external programming vport range with low auxiliary supply support uvlo & aux pins configured for auxiliary supply support 8.5 ? 18 v vhyst_ext uvlo external hysteresis uvlo pin connected to the resistor divider (r1 & r2) ? 15 ? % uvlo_filter uvlo on/off filter time for information only ? 90 ? s auxiliary supply operation ? input supply vaux_min1 vportp ? artn voltage at startup (required for vddh > vddh_por_r) vaux rising ? no external load on vddl & vddh 8.7 ? ? v vaux_min2 vportp ? artn voltage during pwm opera- tion (required for vddh > vddh_por_f) voltage with respect to ivddl_load1 & ivddh_load1 for the load current conditions 8.5 ? ? v 4. test done according to the ieee 802.3af 2 point measurement. the minimum probe voltages measured at the poe ? pd are 1.4 v and 2.4 v, and the maximum probe voltages are 8.5 v and 9.5 v. 5. measured with an external rdet of 25.5 k between vportp and vportn 1,2 , and for 13 v < vport < 20.5 v (with vport = vportp ? vportn 1,2 ). resistors are assumed to have 1% accuracy. 6. this typical current excludes the current in the rclass and rdet external resistors.
ncp1082 http://onsemi.com 8 table 3. operating conditions symbol parameter conditions min typ max unit auxiliary supply operation ? aux pin vaux_off voltage range of the aux pin where the auxiliary supply circuit is guaranteed not operational. voltage with respect to vportn 1,2. ? ? 0.2 v vaux_on voltage range of the aux pin where the auxiliary supply circuit is guaranteed operational. voltage with respect to vportn 1,2 1.5 ? 3.3 v raux total resistance value of the resistor di- vider connected to the aux pin (sum of r aux1 and r aux3 ) between vaux supply & vportn 1,2 ? ? 25 k auxiliary supply operation ? vddl regulator ivddl_load1 current load on the vddl pin with vportp ? artn = 8.5 v (notes 7 and 8) ivddh_load + ivddl_load < 4.5 ma ? ? 1 ma ivddl_load2 current load on the vddl pin with vportp ? artn > 12.5 v (notes 7 and 8) ivddh_load + ivddl_load < 10 ma ? ? 2.25 ma auxiliary supply operation ? vddh regulator ivddh_load1 current load on the vddh regulator with vportp ? artn = 8.5 v (notes 7 and 8) ivddh_load + ivddl_load < 4.5 ma ? ? 4.5 ma ivddh_load2 current load on the vddh regulator with vportp ? artn > 12.5 v (notes 7 and 8) ivddh_load + ivddl_load < 10 ma ? ? 10 ma pass ? switch and current limits ron pass ? switch rds ? on max ron specified at t j = 130 c ? 0.6 1.2 i_rinrush1 rinrush = 150 k (note 9) measured at rtn ? vportn 1,2 = 3 v 95 125 155 ma i_rinrush2 rinrush = 57.6 k (note 9) measured at rtn ? vportn 1,2 = 3 v 260 310 360 ma i_rilim1 rilim1 = 84.5 k (note 9) current limit threshold 450 510 570 ma inrush and ilim1 current limit transition vds_pgood vds required for power good status rtn ? vportnx falling; volt- age with respect to vportn 1,2 0.8 1 1.2 v vds_pgood_hyst vds hysteresis required for power good status voltage with respect to vportn 1,2 ? 8.2 ? v 7. ivddl_load = current flowing out of the vddl pin. ivddh_load = current flowing out of the vddh pin + current delivered to the gate driver (function of the frequency, vddh voltage & mosfet gate capacitance). 8. see figures 6 and 7 for specifications on the load current at lower or higher vpor tp-artn voltages. in case the application requires more current capability on vddl and vddh, it is recommended to externally supply the vddh pin with a bias winding from the transform er or to add a diode between vaux(+) and vddh pin (verify the vaux voltage does not exceed the vddh voltage range). 9. the current value corresponds to the poe ? pd input current (the current flowing in the external rdet and the quiescent current of the device are included). resistors are assumed to have 1% accuracy.
ncp1082 http://onsemi.com 9 table 3. operating conditions symbol parameter conditions min typ max unit vddh regulator vddh_reg regulator output voltage (notes 10 and 11) ivddh_load + ivddl_load < 10 ma with ivddl_load < 2.25 ma and 12.5 v < vportp ? artn < 57 v 8.4 9 9.6 v vddh_off regulator turn ? off voltage for information only ? vddh_reg + 0.5 v ? v vddh_lim vddh regulator current limit (notes 10 and 11) 13 ? 26 ma vddh_por_r vddh por level (rising) 7.3 ? 8.3 v vddh_por_f vddh por level (falling) 6 ? 7 v vddh_ovlo vddh over ? voltage level (rising) 16 ? 18.5 v vddl regulator vddl_reg regulator output voltage (notes 10 and 11) ivddl_load < 2.25 ma with ivddh_load + ivddl_load < 10 ma and 12.5 v < vportp ? artn < 57 v 3.05 3.3 3.55 v vddl_por_r vddl por level (rising) vddl ? 0.2 ? vddl ? 0.02 v vddl_por_f vddl por level (falling) 2.5 ? 2.9 v gate driver gate_tr gate rise time (10 ? 90%) cload = 2 nf, vddhreg = 9 v ? ? 50 ns gate_tf gate fall time (90 ? 10%) cload = 2 nf, vddhreg = 9 v ? ? 50 ns pwm comparator vcomp comp control voltage range for information only 1.3 ? 3 v error amplifier vbg_fb reference voltage voltage with respect to artn 1.15 1.2 1.25 v av_ol dc open loop gain for information only ? 80 ? db gbw error amplifier gbw for information only 1 ? ? mhz soft ? start vss soft ? start voltage range ? 1.15 ? v vss_r soft ? start low threshold (rising edge) 0.35 0.45 0.55 v iss soft ? start source current 3 5 7 a current limit comparator csth cs threshold voltage 324 360 396 mv tblank blanking time for information only ? 100 ? ns 10. power dissipation must be considered. load on vddh and vddl mu st be limited especially if vddh is not powered by an auxiliar y winding. 11. ivddl_load = current flowing out of the vddl pin. ivddh_load = current flowing out of the vddh pin + current delivered to the gate driver (function of the frequency, vddh voltage & mosfet gate capacitance).
ncp1082 http://onsemi.com 10 table 3. operating conditions symbol parameter conditions min. typ. max. units oscillator dutyc maximum duty cycle fixed internally ? 80% ? frange oscillator frequency range 100 ? 500 khz f_acc oscillator frequency accuracy 25 % current consumption ivportp 1 vportp internal current consumption (note 12) dc ? dc controller off ? 2.5 3.5 ma ivportp 2 vportp internal current consumption (note 13) dc ? dc controller on ? 4.7 6.5 ma thermal shutdown tsd thermal shutdown threshold t j = junction temperature 150 ? ? c t j thyst thermal hysteresis t j = junction temperature ? 15 ? c t j thermal ratings ta ambient temperature ? 40 ? 85 c tj junction temperature parametric values guaranteed max 1000 hours ? ? 125 150 c c 12. conditions a. no current through the pass ? switch b. dc ? dc controller inactive (ss shorted to rtn) c. no external load on vddh and vddl d. vportp = 57 v 13. conditions a. no current through the pass ? switch b. oscillator frequency = 100 khz c. no external load on vddh and vddl d. aux winding not used e. 2 nf on gate, dc ? dc controller enabled f. vportp = 57 v figure 6. (ivddl_load)max with auxiliary supply operation figure 7. (ivddh_load+ivddl_load)max with auxiliary supply operation vportp ? artn voltage during pwm opera- tion (v) vportp ? artn voltage during pwm opera- tion (v) 13 12 11.5 11 10.5 10 9.0 8.5 4.0 4.5 5.0 6.5 7.5 8.5 9.5 10.5 0.50 0.75 1.00 1.25 1.75 2.00 2.25 2.50 load current (ma) load current (ma) 9.5 12.5 13.5 5.5 6.0 7.0 8.0 9.0 10.0 13 12 11.5 11 10.5 10 9.0 8.5 9.5 12.5 13.5 1.50
ncp1082 http://onsemi.com 11 description of operation powered device interface the pd interface portion of the ncp1082 supports the ieee 802.3af defined operating modes: detection signature, current source classification, inrush and operating current limits. in order to give more flexibility to the user and also to keep control of the power dissipation in the ncp1082, both current limits are configurable. the device enters operation once its programmable vuvlo_on threshold is reached, and operation ceases when the supplied voltage falls below the vuvlo_off threshold. sufficient hysteresis and uvlo filter time are provided to avoid false power on/off cycles due to transient voltage drops on the cable. detection during the detection phase, the incremental equivalent resistance seen by the pse through the cable must be in the ieee 802.3af standard specification range (23.75 k to 26.25 k ) for a pse voltage from 2.7 v to 10.1 v. in order to compensate for the non ? linear effect of the diode bridge and satisfy the specification at low pse voltage, the ncp1082 presents a suitable impedance in parallel with the 25.5 k r det external resistor connected between vportp and vportn. for some types of diodes (especially schottky diodes), it may be necessary to adjust this external resistor. when the detection_off level is detected (typically 11.5 v) on vportp, the ncp1082 turns on its internal 3.3 v regulator and biasing circuitry in anticipation of the classification phase as the next step. classification once the pse device has detected the pd device, the classification process begins. in classification, the pd regulates a constant current source that is set by the external resistor rclass value on the class pin. figure 8 shows the schematic overview of the classification block. the current source is defined as: i class v bg r class , (where v bg is 1.2 v) class vdda1 1.2 v vportp vportn1,2 ncp1082 rclass figure 8. classification block diagram power mode when the classification hand ? shake is completed, the pse and pd devices move into the operating mode. under voltage lock out (uvlo) the ncp1082 incorporates an under voltage lock out (uvlo) circuit which monitors the input voltage and determines when to apply power to the dc ? dc controller. to use the default settings for uvlo (see t able 3), the pin uvlo must be connected to vportn 1,2 . in this case the signature resistor has to be placed directly between vportp and vportn 1,2 , as shown in figure 9. figure 9. default uvlo settings uvlo vportp vportn1,2 ncp1082 vport rdet to define the uvlo threshold externally, the uvlo pin must be connected to the center of an external resistor divider between vportp and vportn 1,2 as shown in figure 10. the series resistance value of the external resistors must add to 25.5 k and replaces the internal signature resistor. figure 10. external uvlo configuration uvlo vportn1,2 ncp1082 vport r2 r1 vportp for a vuvlo_on desired turn ? on voltage threshold, r1 and r2 can be calculated using the following equations: r1 r2 r det r2 1.2 v ulvo_on r det when using the external resistor divider, the ncp1082 has an external reference voltage hysteresis of 15 percent typical.
ncp1082 http://onsemi.com 12 auxiliary supply support to support applications connected to non poe enabled networks and minimize the bill of materials, the ncp1082 supports drawing power from an external supply. the ncp1082 supports the ieee 802.3af standard when the poe capability is available and acts as a regular dc-dc converter when there is no power source on the ethernet cable as shown in figure 11. auxiliary supply support can be implemented in three ways depending on where the auxiliary supply is injected. the front, rear and direct auxiliary supply configurations are explained in more detail in the application note and9080. uvlo vportn1,2 ncp1082 vportp rdet1 raux2 vaux(+) rdet2 pass switch rtn raux1 raux3 aux d1 d2 poe(+) poe( ? ) vport cpd dc ? dc stage vaux( ? ) to vportn1,2 (front aux configuration) to rtn (rear aux configuration) or figure 11. front and rear auxiliary supply input with support for very low input voltages optional ? for very low vaux only when the auxiliary input supply is above 13.5 v, connect the aux pin to vportn 1,2. . when the auxiliary supply is below 13.5 v (but above 9 v), calculate the voltage dividers raux1, raux3 and raux2, rdet1, rdet2 to divide the input voltage using the below formulas together with the formulas from the previous section. this will ensure that for valid input voltages, the voltage at the uvlo and aux pins are above their threshold voltages. note that the maximum voltage is 3.3 v. r aux3 r aux1 v t v aux v dp v t r aux1 20 k r aux2 v aux v dp v d v t v t 845 v aux v dp v d v t 24 k where v d is the voltage drop over the rectifiers and masking diodes (typical 0.6 v), v dp is the forward drop of the ncp1082 internal diode (typical 0.5 v), and v t is the threshold voltage on the aux pin (typical 1.5 v). note that as soon the auxiliary supply is connected the poe interface (detection and classification) is disabled and does not allow the pd device to be powered from the ethernet until the auxiliary supply is removed. if the poe pd device was drawing the current from the ethernet cable before the auxiliary supply is connected, the power will continue to be supplied from the ethernet cable unless the voltage of the auxiliary supply is higher than the ethernet supply voltage. inrush and operational current limitations the inrush current limit and the operational current limit are programmed individually by an external rinrush and rilim1 resistors respectively connected between inrush and vportn 1,2 , and between ilim1 and vportn 1,2 as shown in figure 12. ilim1 / inrush vdda1 vbg1 vdda1 vportnx ilim_ref ncp1082 figure 12. current limitation configuration (inrush & ilim1 pins)
ncp1082 http://onsemi.com 13 ilim1 vds_pgood threshold vportnx pass switch inrush i_pass_switch ncp1082 rtn vds_pgood 0 1 vdda1 vdda1 1 v / 9.2 v 2 v current_limit_on & detector figure 13. inrush and ilim1 selection mechanism vdda1 when vport reaches the uvlo_on level, the cpd capacitor is charged with the inrush current (in order to limit the internal power dissipation of the pass ? switch). once the cpd capacitor is fully charged, the current limit switches from the inrush current to the operational current level (ilim1) as shown in figure 13. this transition occurs when both following conditions are satisfied: 1. the vds of the pass ? switch is below the vds_pgood low level (1 v typical). 2. the pass ? switch is no longer in current limit mode, meaning the gate of the pass ? switch is ?high? (above 2 v typical). the operational current limit will stay selected as long as vds_pgood is true (meaning that rtn ? vportn 1,2 is below the high level of vds_pgood). this mechanism allows a current level transition without any current spike in the pass ? switch because the operational current limit (ilim1) is enabled once the pass ? switch is not limiting the current anymore, meaning that the cpd capacitor is fully charged. thermal shutdown the ncp1082 includes thermal protection which shuts down the device in case of high power dissipation. once the thermal shutdown (tsd) threshold is exceeded, following blocks are turned off: ? dc ? dc controller ? pass ? switch ? vddh and vddl regulators ? class regulator when the tsd error disappears and if the input line voltage is still above the uvlo level, the ncp1082 automatically restarts with the current limit set in the inrush state, the dc ? dc controller is disabled and the css (soft ? start capacitor) discharged. the dc ? dc controller becomes operational as soon as rtn ? vportn 1,2 is below the vds_pgood threshold.
ncp1082 http://onsemi.com 14 dc ? dc converter controller the ncp1082 implements a current mode dc ? dc converter controller which is illustrated in figure 14. vddl fb cs 360 mv oscillator comp ss gate driver pwm comp osc vddl vddl blanking time current slope compensation 2 soft ? start r s q 1.45 v 1.2 v current limit comp 0 9 v ldo 3.3 v ldo gate vddh artn vportp set clk reset clk figure 14. dc ? dc controller block diagram 5 k 10 a 11 k 5 a & sawtooth generator internal vddh and vddl regulators and gate driver an internal linear regulator steps down the vportp voltage to a 9 v output on the vddh pin. vddh supplies the internal gate driver circuit which drives the gate pin and the gate of the external power mosfet. the ncp1082 gate driver supports an external mosfet with high vth and high input gate capacitance. a second ldo regulator steps down the vddh voltage to a 3.3 v output on vddl. vddl powers the analog circuitry of the dc ? dc controller. in order to prevent uncontrolled operations, both regulators include power ? on ? reset (por) detectors which prevent the dc ? dc controller from operating when either vddh or vddl is too low. in addition, an over ? voltage lockout (ovlo) on the vddh supply disables the gate driver in case of an open ? loop converter with a configuration using the bias winding of the transformer (see figure 4). both vddh and vddl regulators turn on as soon as vport reaches the vuvlo_on threshold. error amplifier in non ? isolated converter topologies, the high gain internal error amplifier of the ncp1082 and the internal 1.2 v reference voltage regulate the dc ? dc output voltage. in this configuration, the feedback loop compensation network should be inserted between the fb and comp pins as shown in figures 3, 4 and 5. in isolated topologies the error amplifier is not used because it is already implemented externally with the shunt regulator on the secondary side of the dc ? dc controller (see figure 2). therefore the fb pin must be strapped to artn and the output transistor of the opto ? coupler has to be connected on the comp pin where an internal 5 k pull ? up resistor is tied to the vddl supply (see figure 14). soft ? start the soft ? start function provided by the ncp1082 allows the output voltage to ramp up in a controlled fashion, eliminating output voltage overshoot. this function is programmed by connecting a capacitor c ss between the ss and artn pins. while the dc ? dc controller is in por, the capacitor c ss is fully discharged. after coming out of por, an internal current source of 5 a typically starts charging the capacitor c ss to initiate soft ? start. when the voltage on ss pin has reached 0.45 v (typical), the gate driver is enabled and dc ? dc operation starts with a duty cycle limit which increases with the ss pin voltage. the soft ? start function is finished when the ss pin voltage goes above 1.6 v for which the duty cycle limit reaches its maximum value of 80 percent. soft ? start can be programmed by using the following equation: t ss (ms) 0.23 c ss (nf)
ncp1082 http://onsemi.com 15 current limit comparator the ncp1082 current limit block behind the cs pin senses the current flowing in the external mosfet for current mode control and cycle ? by ? cycle current limit. this is performed by the current limit comparator which, on the cs pin, senses the voltage across the external rcs resistor located between the source of the mosfet and the artn pin. the ncp1082 also provides a blanking time function on cs pin which ensures that the current limit and pwm comparators are not prematurely trigged by the current spike that occurs when the switching mosfet turns on. slope compensation circuitry to overcome sub ? harmonic oscillations and instability problems that exist with converters running in continuous conduction mode (ccm) and when the duty cycle is close or above 50 percent, the ncp1082 integrates a current slope compensation circuit. the amplitude of the added slope compensation is typically 110 mv over one cycle. as an example, for an operating switching frequency of 250 khz, the internal slope provided by the ncp1082 is 27.5 mv/ a typically. dc ? dc controller oscillator the frequency is configured with the rosc resistor inserted between osc and artn, and is defined by the following equation: r osc (k ) 38600 f osc (khz) the duty cycle limit is fixed internally at 80 percent.
ncp1082 http://onsemi.com 16 package dimensions ? 20 ep case 948ab ? 01 issue o dim d min max 6.60 millimeters e1 4.30 4.50 a 1.10 a1 0.05 0.15 l 0.50 0.70 e 0.65 bsc p --- 4.20 c 0.09 0.20 c1 0.09 0.16 b 0.19 0.30 b1 0.19 0.25 l2 0.25 bsc m 0 8 notes: 1. dimensioning and tolerancing per asme y14.5m, 1994. 2. controlling dimension: millimeters. 3. dimension b does not include dambar protrusion. allowable dambar protrusion shall be 0.07 in excess of the lead width at mmc. dambar cannot be loacted on the lower radius or the foot of the lead. 4. dimensions b, b1, c, c1 to be measured be- tween 0.10 and 0.25 from lead tip. 5. datums a and b are are determined at datum h. datum h is loacted at the mold parting line and coincident with lead where the lead exits the plastic body. 6. dimension d does not include mold flash, protrusions or gate burrs. mold flash, protrusions or gate burrs shall not exceed 0.15 per side. dimension e1 does not include interlead flash or protrusion. in- terlead flash or protrusion shall not ex- ceed 0.15 per side. d and e1 are determined at datum h. pin 1 reference d e1 0.08 a section b ? b b b1 cc1 seating plane 20x b e e detail a 6.40 --- 4.30 20x 0.98 20x 0.35 0.65 dimensions: millimeters pitch soldering footprint* l l2 gauge detail a e/2 detail b a2 0.85 0.95 e 6.40 bsc p1 --- 3.00 plane seating plane c h b b b m end view a-b m 0.10 d c top view side view a-b 0.20 d c 110 11 20 b a d detail b 2x 10 tips a1 a2 c 0.05 c c p p1 bottom view 3.10 6.76 20x *for additional information on our pb ? free strategy and soldering details, please download the on semiconductor soldering and mounting techniques reference manual, solderrm/d.
ncp1082 http://onsemi.com 17 on semiconductor and are registered trademarks of semiconductor co mponents industries, llc (scillc). scillc owns the rights to a numb er of patents, trademarks, copyrights, trade secrets, and other inte llectual property. a listing of scillc?s pr oduct/patent coverage may be accessed at ww w.onsemi.com/site/pdf/patent ? marking.pdf. scillc reserves the right to make changes without further notice to any products herein. scillc makes no warranty, representation or guarantee regarding the suitability of its products for any particular purpose, nor does scillc assume any liability arising out of the application or use of any product or circuit, and s pecifically disclaims any and all liability, including without limitation special, consequential or incidental damages. ?typical? parameters which may be provided in scillc data sheets and/ or specifications can and do vary in different applications and actual performance may vary over time. all operating parameters, including ?typical s? must be validated for each customer application by customer?s technical experts. scillc does not convey any license under its patent rights nor the right s of others. scillc products are not designed, intended, or a uthorized for use as components in systems intended for surgical implant into the body, or other applications intended to support or sustain life, or for any other application in whic h the failure of the scillc product could create a situation where personal injury or death may occur. should buyer purchase or us e scillc products for any such unintended or unauthorized appli cation, buyer shall indemnify and hold scillc and its officers, employees, subsidiaries, affiliates, and distributors harmless against all claims, costs, damages, and expenses, and reasonable attorney fees arising out of, directly or indirectly, any claim of personal injury or death associated with such unin tended or unauthorized use, even if such claim alleges that scil lc was negligent regarding the design or manufacture of the part. scillc is an equal opportunity/affirmative action employer. this literature is subject to all applicable copyrig ht laws and is not for resale in any manner. publication ordering information n. american technical support : 800 ? 282 ? 9855 toll free usa/canada europe, middle east and africa technical support: phone: 421 33 790 2910 japan customer focus center phone: 81 ? 3 ? 5817 ? 1050 ncp1082/d literature fulfillment : literature distribution center for on semiconductor p.o. box 5163, denver, colorado 80217 usa phone : 303 ? 675 ? 2175 or 800 ? 344 ? 3860 toll free usa/canada fax : 303 ? 675 ? 2176 or 800 ? 344 ? 3867 toll free usa/canada email : orderlit@onsemi.com on semiconductor website : www.onsemi.com order literature : http://www.onsemi.com/orderlit for additional information, please contact your local sales representative

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