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general description the max5904?ax5909 dual hot-swap controllers provide complete protection for dual-supply systems. these devices hot swap two supplies ranging from +1v to +13.2v, provided one supply is at or above 2.7v, allowing the safe insertion and removal of circuit cards into live backplanes. the discharged filter capacitors of the circuit card pro- vide low impedance to the live backplane. high inrush currents from the backplane to the circuit card can burn up connectors and components, or momentarily col- lapse the backplane power supply leading to a system reset. the max5904 family of hot-swap controllers pre- vents such problems by gradually ramping up the output voltage and regulating the current to a preset limit when the board is plugged in, allowing the system to stabilize safely. after the startup cycle is completed, two on-chip comparators provide variablespeed/bilevel protec- tion against short-circuit and overcurrent faults, as well as immunity against system noise and load transients. in the event of a fault condition, the load is disconnected. the MAX5905/max5907/max5909 must be unlatched after a fault, and the max5904/max5906/max5908 auto- matically restart after a fault. the max5904 family offers a variety of options to reduce component count and design time. all devices integrate an on-board charge pump to drive the gates of low-cost, external n-channel mosfets. the devices offer integrat- ed features like startup current regulation and current glitch protection to eliminate external timing resistors and capacitors. the max5906?ax5909 provide an open- drain status output, an adjustable startup timer, an adjustable current limit, an uncommitted comparator, and output undervoltage/overvoltage monitoring. the max5904/MAX5905 are available in 8-pin so pack- ages. the max5906?ax5909 are available in space- saving 16-pin qsop packages. applications pci-express applications basestation line cards network switches or routers solid-state circuit breaker power-supply sequencing hot plug-in daughter cards raid features safe hot swap for +1v to +13.2v power supplies requires one input 2.7v low 25mv default current-limit threshold inrush current regulated at startup circuit breaker function adjustable circuit breaker/current-limit threshold variablespeed/bilevel circuit-breaker response auto-retry or latched fault management on/off sequence programming status output indicates fault/safe condition output undervoltage and overvoltage monitoring and/or protection max5904?ax5909 low-voltage, dual hot-swap controllers/power sequencers ________________________________________________________________ maxim integrated products 1 gate2 ongnd 1 2 8 7 in2 sense2sense1 gate1 in1 narrow so top view 3 4 6 5 max5904 MAX5905 pin configurations ordering information 19-2238; rev 2; 11/03 evaluation kit available for pricing, delivery, and ordering information, please contact maxim/dallas direct! at 1-888-629-4642, or visit maxim? website at www.maxim-ic.com. part temp range pin-package max5904 esa* -40 c to +85 c 8 so max5904usa 0 c to +85 c 8 so MAX5905 esa* -40 c to +85 c 8 so MAX5905usa 0 c to +85 c 8 so max5906 eee* -40 c to +85 c 16 qsop max5906uee 0 c to +85 c 16 qsop max5907 eee* -40 c to +85 c 16 qsop max5907uee 0 c to +85 c 16 qsop max5908 eee* -40 c to +85 c 16 qsop max5908uee 0 c to +85 c 16 qsop max5909 eee* -40 c to +85 c 16 qsop max5909uee 0 c to +85 c 16 qsop selector guide and typical operating circuits appear at end of data sheet. variablespeed/bilevel is a trademark of maxim integrated products, inc. pin configurations continued at end of data sheet. * contact factory for availability.
max5904?ax5909 low-voltage, dual hot-swap controllers/power sequencers 2 _______________________________________________________________________________________ absolute maximum ratings electrical characteristics (v in _ = +1v to +13.2v provided at least one supply is higher than +2.7v, v on = +2.7v, t a = t min to t max , unless otherwise noted. typical values are at v in1 = +5v, v in2 = +3.3v, and t a = +25 c.) (note 1) stresses beyond those listed under ?bsolute 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. in_ to gnd...........................................................................+14v gate_ to gnd..........................................+0.3v to (v in _ + 6.2v) on, pgood, comp+, compout, tim to gnd.......-0.3v to the higher of (v in1 + 0.3v) and (v in2 + 0.3v) sense_, mon_, lim_ to gnd ...................-0.3v to (v in _ + 0.3v) current into any pin .........................................................50ma continuous power dissipation (t a = +70 c) 8-pin narrow so (derate 5.9mw/ c above +70 c) ......471mw 16-pin qsop (derate 8.3mw/ c above +70 c)............667mw operating temperature ranges: max590_u_ _ .....................................................0 c to +85 c max590_e_ _ ...................................................-40 c to +85 c storage temperature range .............................-65 c to +150 c parameter symbol conditions min typ max units power supplies in_ input voltage range v in _ other v in = +2.7v 1.0 13.2 v supply current i in i in1 + i in2 1.2 2.3 ma current control t a = +25 c 22.5 25 27.5 max5904/MAX5905 t a = t min to t max 20.5 27.5 lim = gnd 22.5 25 27.5 slow-comparator threshold (v in - v sense ) (note 2) v sc , th max5906 max5909 r lim = 300k ? 80 100 125 mv 1mv overdrive 3 ms slow-comparator response time (note 3) t scd 50mv overdrive 110 s v su , th v in _ - v sense _; during startup 2 x v sc, th fast-comparator threshold v fc , th v in _ - v sense _; normal operation 4 x v sc, th mv fast-comparator response time t fcd 10mv overdrive, from overload condition 260 ns sense input bias current i b sen v sen _ = v in _ 0.03 6 a mosfet driver r tim = 100k ? 8 10.8 13.6 r tim = 4k ? (minimum value) 0.35 0.45 0.55 startup period (note 4) t start tim floating for max5906 max5909 fixed for max5904/MAX5905 5914 ms charging, v gate = +5v, v in = +10v (note 5) 80 100 130 a weak discharge, during startup when current limit is active or when 0.4v < v on < 0.8v 100 a average gate current i gate strong discharge, triggered by a fault or when v on < 0.4v 3ma gate drive voltage v drive v gate _ - v in _, i gate _ < 1a 4.8 5.4 5.8 v on comparator low to high 0.375 0.4 0.425 v fast pulldown on threshold v onfp , th hysteresis 25 mv
max5904?ax5909 low-voltage, dual hot-swap controllers/power sequencers _______________________________________________________________________________________ 3 note 1: limits are 100% tested at t a = +25 c and +85 c. limits at 0 c and -40 are guaranteed by characterization and are not produc- tion tested. note 2 the max5906 max5909 slow-comparator threshold is adjustable. v sc,th = r lim x 0.25a + 25mv (see typical operating characteristics ). note 3: the current-limit slow-comparator response time is weighted against the amount of overcurrent; the higher the overcurrent condition, the faster the response time. see typical operating characteristics . note 4: the startup period (t start ) is the time during which the slow comparator is ignored and the device acts as a current limiter by regulating the sense current with the fast comparator. see the startup period section. electrical characteristics (continued) (v in _ = +1v to +13.2v provided at least one supply is higher than +2.7v, v on = +2.7v, t a = t min to t max , unless otherwise noted. typical values are at v in1 = +5v, v in2 = +3.3v, and t a = +25 c.) (note 1) parameter symbol conditions min typ max units low to high 0.80 0.825 0.85 v channel 1 on threshold v on1 , th hysteresis 25 mv low to high 1.95 2.025 2.07 v channel 2 on threshold v on2 , th hysteresis 25 mv on propagation delay t on 10mv overdrive 50 s v on < 4.5v 0.03 v on > 4.5v 100 on input bias current i bon v in1 = v in2 = +13.2v v on = 4v 0.03 1 a on pulse width low t unlatch to unlatch after a latched fault 100 s digital output (pgood) output leakage current v pgood = 13.2v 1 a output voltage low v ol i sink = 1ma 0.4 v pgood delay t pgdly after t start , mon_ = v in_ 0.75 ms output voltage monitors (mon1, mon2) overvoltage 657 687 707 mon_ trip threshold v mon _ undervoltage 513 543 563 mv mon_ glitch filter 20 s mon_ input bias current v mon _ = 600mv 0.03 a undervoltage lockout (uvlo) s tar tup i s i ni ti ated w hen thi s thr eshol d i s r eached b y v in 1 or v in 2 , v on > 0.8v , v in_ i ncr easi ng 2.1 2.4 2.67 v uvlo threshold v uvlo hysteresis 100 mv uvlo glitch filter reset time v in _ = 0v, to unlatch after a fault 100 s uvlo to startup delay t d , uvlo v in_ step from 0 to 2.8v 20 37.5 60 ms shutdown restart auto-retry delay t retry delay time to restart after a fault shutdown max5904/max5906/max5908 64 x t start ms uncommitted comparator low to high 1.206 1.236 1.266 v inc+ trip threshold voltage v c,th hysteresis 10 mv propagation delay 10mv overdrive 50 s outc voltage low v ol i sink = 1ma 0.4 v inc+ bias current v inc+ = 5v 0.02 1 a outc leakage current i outc v outc = 13.2v 0.02 1 a
max5904?ax5909 low-voltage, dual hot-swap controllers/power sequencers 4 _______________________________________________________________________________________ typical operating characteristics (typical operating circuits, q1 = q2 = fairchild fdb7090l, v in1 = +5v, v in2 = +3.3v, t a = +25 c, unless otherwise noted. channels 1 and 2 are identical in performance. where characteristics are interchangeable, channels 1 and 2 are referred to as x and y.) 0 0.6 0.4 0.2 1.0 0.8 1.8 1.6 1.4 1.2 2.0 02468101214 supply current vs. supply voltage max5904 toc01 v inx (v) i in (ma) v iny = v on = 2.7v i inx + i iny i inx i iny 0 0.6 0.4 0.2 1.0 0.8 1.8 1.6 1.4 1.2 2.0 02468101214 total supply current vs. supply voltage max5904 toc02 v inx (v) i in (ma) v iny = 5.0v a) v on = 3.3v b) v on = 1.5v c) v on = 0v a c b 0 0.6 0.4 0.2 0.8 1.0 1.2 1.4 1.6 1.8 2.0 -40 10 -15 35 60 85 supply current vs. temperature max5904 toc03 temperature ( c) i in (ma) v on = v in1 i in1 + i in2 i in2 i in1 0 2 1 4 3 5 6 068 2 4 10 12 14 gate drive voltage vs. input voltage max5904 toc04 v inx (v) gate drive voltage (v) v iny = 2.7v 0 60 40 20 80 100 120 140 160 180 200 020 gate charge current vs. gate voltage max5904 toc05 v gatex (v) gate charge current ( a) 51015 v on = v iny = 2.7v v inx = 13.2v v inx = 5v v inx = 1v 0 60 40 20 80 100 120 140 160 180 200 -40 10 -15 35 60 85 gate charge current vs. temperature max5904 toc06 temperature ( c) gate charge current ( a) v inx = 13.2v v inx = 5v v inx = 1v v on = v iny = 2.7v v gatex = 0v 0 60 40 20 80 100 120 140 160 180 200 05 15 10 20 gate weak discharge current vs. gate voltage max5904 toc07 v gatex (v) gate discharge current ( a) v on = 0.6v v iny = 2.7v v inx = 13.2v v inx = 5v v inx = 1v 0 60 40 20 80 100 120 140 160 180 200 -40 -15 35 60 10 85 gate weak discharge current vs. temperature max5904 toc08 temperature ( c) gate discharge current ( a) v on = 0.6v v inx = 13.2v v inx = 5v v inx = 1v v iny = 2.7v v gatex = v inx + 6.2v 0 2 1 4 3 5 6 010 51520 gate strong discharge current vs. gate voltage max5904 toc09 v gatex (v) gate discharge current (ma) v inx = 13.2v v inx = 5v v inx = 1v v on = 0v v iny = 2.7v v gatex = v inx + 6.2v
max5904?ax5909 low-voltage, dual hot-swap controllers/power sequencers _______________________________________________________________________________________ 5 0 2 1 4 3 5 6 -40 10 -15 35 60 85 gate strong discharge current vs. temperature max5904 toc10 temperature ( c) gate discharge current (ma) v inx = 13.2v v inx = 5v v inx = 1v v on = 0v v iny = 2.7v v gatex = v inx + 6.2v 0.0001 0.001 0.1 0.01 1 10 05075 25 100 125 150 175 200 turn-off time vs. sense voltage max5904 toc11 v in - v sense (mv) turn-off time (ms) slow-comp. threshold fast-comp. threshold 0.1 1 10 20 30 35 25 40 45 50 55 60 65 70 75 80 turn-off time vs. sense voltage (expanded scale) max5904 toc12 v in - v sense (mv) turn-off time (ms) slow-comp. threshold 0 40 20 80 60 100 120 0 200 100 300 400 slow-comparator threshold vs. r lim max5904 toc13 r lim (k ? ) v sc, th (mv) 0 20 10 40 30 50 60 startup period vs. r tim max5904 toc14 r tim (k ? ) t start (ms) 0 200 300 100 400 500 600 0v 0v 0v v pgood 5v/div v sense - v in 100mv/div v gate 5v/div turn-off time slow-comparator fault max5904 toc15 1ms/div v in = 5.0v t scd 26mv step 0v 0v 0v v pgood 5v/div v sense - v in 100mv/div v gate 5v/div turn-off time fast-comparator fault max5904 toc16 400ns/div v in = 5.0v t fcd 125mv step v on 2v/div v pgood 2v/div i out 5a/div v out 5v/div v gate 5v/div startup waveforms fast turn-on max5904 toc17 1ms/div v in = 5.0v, r sense = 10m ? , r tim = 27k ? , c board = 1000 f typical operating characteristics (continued) (typical operating circuits, q1 = q2 = fairchild fdb7090l, v in1 = +5v, v in2 = +3.3v, t a = +25 c, unless otherwise noted. channels 1 and 2 are identical in performance. where characteristics are interchangeable, channels 1 and 2 are referred to as x and y.)
max5904?ax5909 low-voltage, dual hot-swap controllers/power sequencers 6 _______________________________________________________________________________________ pin description pin max5904/ MAX5905 max5906 max5909 name function 1 pgood open-drain status output. high impedance when startup is complete and no faults are detected. actively held low during startup and when a fault is detected. 2 tim startup timer setting. connect a resistor from tim to gnd to set the startup period. leave tim unconnected for the default startup period of 9ms. 1 3 in1 channel 1 supply input. connect to a supply voltage from 1v to 13.2v. connect a 0.1f ceramic bypass capacitor from in1 to gnd to filter high-frequency noise. 2 4 sense1 channel 1 current-sense input. connect r sense1 from in1 to sense1. 3 5 gate1 channel 1 gate-drive output. connect to gate of external n-channel mosfet. 4 6 gnd ground 7 lim1 channel 1 current-limit setting. connect a resistor from lim1 to gnd to set current-trip level. connect to gnd for the default 25mv threshold. 8 mon1 channel 1 output voltage monitor. window comparator input. connect through a resistive-divider from out1 to gnd to set the channel 1 overvoltage and undervoltage thresholds. connect to in1 to disable. 9 mon2 channel 2 output voltage monitor. window comparator input. connect through a resistive-divider from out2 to ground to set the channel 2 overvoltage and undervoltage thresholds. connect to in2 to disable. i out 5a/div v out 5v/div v gate 5v/div auto-retry delay max5904 toc19 40ms/div v in = 5.0v, r sense = 10m ? , r tim = 47k ? , c board = 1000 f, r board = 1.4 ? v on 2v/div v pgood 2v/div i out 5a/div v out 5v/div v gate 5v/div startup waveforms slow turn-on max5904 toc18 1ms/div v in = 5.0v, r sense = 10m ? , r tim = 47k ? , c board = 1000 f, c gate = 22nf typical operating characteristics (continued) (typical operating circuits, q1 = q2 = fairchild fdb7090l, v in1 = +5v, v in2 = +3.3v, t a = +25 c, unless otherwise noted. channels 1 and 2 are identical in performance. where characteristics are interchangeable, channels 1 and 2 are referred to as x and y.)
detailed description the max5904 max5909 are circuit breaker ics for hot- swap applications where a line card is inserted into a live backplane. these devices hot swap supplies rang- ing from +1v to +13.3v, provided one supply is at or above 2.7v. normally, when a line card is plugged into a live backplane, the card s discharged filter capacitors provide low impedance that can momentarily cause the main power supply to collapse. the max5904 max5909 reside either on the backplane or on the removable card to provide inrush current limiting and short-circuit protection. this is achieved by using exter- nal n-channel mosfets, external current-sense resis- tors, and two on-chip comparators. figure 1 shows the max5906 max5909 functional diagram. the max5904/MAX5905 have a fixed startup period and current-limit threshold. the startup period and cur- rent-limit threshold of the max5906 max5909 can be adjusted with external resistors. startup period r tim sets the duration of the startup period for the max5906 max5909 from 0.4ms to 50ms (see the setting the startup period section). the duration of the startup period is fixed at 9ms for the max5904/ MAX5905. the startup period begins after the following three conditions are met: 1) v in1 or v in2 exceeds the uvlo threshold (2.4v) for the uvlo to startup delay (37.5ms). 2) v on exceeds the channel 1 on threshold (0.825v). 3) the device is not latched or in its auto-retry delay. (see latched and auto-retry fault management.) the max5904 max5909 limit the load current if an overcurrent fault occurs during startup. the slow com- parator is disabled during the startup period and the load current can be limited in two ways: 1) slowly enhancing the mosfets by limiting the mosfet gate charging current 2) limiting the voltage across the external current- sense resistor. during the startup period the gate drive current is typi- cally 100a and decreases with the increase of the gate voltage (see typical operating characteristics ). this allows the controller to slowly enhance the mosfets. if the fast comparator detects an overcur- rent, the max5904 max5909 regulate the gate voltage to ensure that the voltage across the sense resistor does not exceed v su,th . this effectively regulates the inrush current during startup. figure 2 shows the start- up waveforms. pgood goes high impedance 0.75ms after the startup period if no fault condition is present. variablespeed/bilevel fault protection variablespeed/bilevel fault protection incorporates two comparators with different thresholds and response times to monitor the load current ( figure 9 ). during the startup period, protection is provided by limiting the load current. protection is provided in normal operation (after the startup period has expired) by discharging both mosfet gates with a strong 3ma pulldown cur- rent in response to a fault condition. after a fault, max5904?ax5909 low-voltage, dual hot-swap controllers/power sequencers _______________________________________________________________________________________ 7 pin max5904/ MAX5905 max5906 max5909 name function 10 lim2 channel 2 current-limit setting. connect a resistor from lim2 to gnd to set current-trip level. connect to gnd for the default 25mv threshold. 5 11 on on comparator input 6 12 gate2 channel 2 gate-drive output. connect to gate of external n-channel mosfet. 7 13 sense2 channel 2 current-sense input. connect r sense2 from in2 to sense2. 8 14 in2 channel 2 supply input. connect to a supply voltage from 1v to 13.2v. connect a 0.1f ceramic bypass capacitor from in2 to gnd to filter high-frequency noise. 15 inc+ uncommitted comparator noninverting input 16 outc uncommitted comparator open-drain output. actively held low when v inc+ is less than 1.236v. pin description (continued)
max5904?ax5909 low-voltage, dual hot-swap controllers/power sequencers 8 _______________________________________________________________________________________ uvlo fast comp. slow comp. slow discharge fast discharge q1 out1 2.4v 2.4v bias and references timing oscillator startup oscillator to startup logic blocks charge pump device control logic v sc, th v fs, th r lim1 sense1 in1 gate1 r sense1 lim1 n r lim2 n 100 a 3ma 687mv 543mv 1.236v mon1 inc+ outc on pgood uvlo fast comp. slow comp. slow discharge fast discharge q2 out2 charge pump oscillator to startup logic blocks charge pump current control and startup logic current control and startup logic v sc, th v fs, th sense2 in2 gate2 r sense2 lim2 100 a 3ma 687mv 543mv mon2 max5906 max5907 max5908 max5909 2.025v 0.825v 0.4v r tim tim figure 1. max5906?ax5909 functional diagram
pgood is pulled low, the MAX5905/max5907/ max5909 stay latched off and the max5904/max5906/ max5908 automatically restart. slow comparator startup period the slow comparator is disabled during the startup period while the external mosfets are turning on. disabling the slow comparator allows the device to ignore the higher-than-normal inrush current charging the board capacitors when a card is first plugged into a live backplane. slow comparator normal operation after the startup period is complete the slow compara- tor is enabled and the device enters normal operation. the comparator threshold voltage (v sc,th) is fixed at 25mv for the max5904/MAX5905 and is adjustable from 25mv to 100mv for the max5906 max5909. the slow comparator response time decreases to a mini- mum of 110s with a large overdrive voltage ( figure 9 ). response time is 3ms for a 1mv overdrive. the variable speed response time allows the max5904 max5909 to ignore low-amplitude momentary glitches, thus increas- ing system noise immunity. after an extended overcur- rent condition, a fault is generated, pgood is pulled low, and the mosfet gates are discharged with a strong 3ma pulldown current. fast comparator startup period during the startup period the fast comparator regulates the gate voltage to ensure that the voltage across the sense resistor does not exceed v su,th . the startup fast-comparator threshold voltage (v su,th ) is scaled to two times the slow-comparator threshold (v sc,th ). fast comparator normal operation in normal operation, if the load current reaches the fast- comparator threshold, a fault is generated, pgood is pulled low, and the mosfet gates are discharged with a strong 3ma pulldown current. this happens in the event of a serious current overload or a dead short. the fast-comparator threshold voltage (v fc,th ) is scaled to four times the slow-comparator threshold (v sc,th ). this comparator has a fast response time of 260ns ( figure 9 ). undervoltage lockout (uvlo) the undervoltage lockout prevents the max5904 max5909 from turning on the external mosfets until one input voltage exceeds the uvlo threshold (2.4v) for t d,uvlo . the max5904 max5909 use power from the higher input voltage rail for the charge pumps. this allows for more efficient charge-pump operation. the uvlo protects the external mosfets from an insuffi- cient gate drive voltage. t d,uvlo ensures that the board is fully inserted into the backplane and that the input voltages are stable. any input voltage transient on both supplies below the uvlo threshold will reinitiate the t d,uvlo and the startup period. latched and auto-retry fault management the MAX5905/max5907/max5909 latch the external mosfets off when a fault is detected. toggling on below 0.4v or one of the supply voltages below the uvlo threshold for at least 100s clears the fault latch and reinitiates the startup period. similarly, the max5904/max5906/max5908 turn the external mosfets off when a fault is detected then automatical- ly restart after the auto-retry delay that is internally set to 64 times t start . during the auto-retry delay, toggling on below 0.4v does not clear the fault. the auto-retry can be overridden causing the startup period to begin immediately by toggling one of the supply voltages below the uvlo threshold. output voltage monitor the MAX5905 max5909 monitor the output voltages with the mon1 and mon2 window comparator inputs. these voltage monitors are enabled after the startup period. once enabled, the voltage monitor detects a fault if v mon _ is less than 543mv or greater than 687mv. if an output voltage fault is detected pgood pulls low. when the max5906/max5907 detect an out- max5904?ax5909 low-voltage, dual hot-swap controllers/power sequencers _______________________________________________________________________________________ 9 t on 4.8v to 5.8v v gate v gate pgood on v th v out v out i load t start + t pgdly c board = large c board = 0 v su,th r sense figure 2. startup waveforms
max5904?ax5909 low-voltage, dual hot-swap controllers/power sequencers 10 ______________________________________________________________________________________ t pgdly v on_,th v on v gate_ v out_ internal signal internal signal pgood t start figure 3. power-up with on pin control (at least one v in_ is > v uvlo ) timing diagrams
max5904?ax5909 low-voltage, dual hot-swap controllers/power sequencers ______________________________________________________________________________________ 11 i out v gate_ v out_ pgood t scd discharge rate depends on output loading overcurrent condition (v in_ - v sense_ v sc_th and v in_ - v sense_ < v fc_th ) figure 4. power-down when an overcurrent fault occurs i out v gate_ v out_ pgood t fcd short-circuit condition (v in_ - v sense_ v fc_th ) figure 5. power-down when a short-circuit fault occurs timing diagrams (continued)
max5904?ax5909 low-voltage, dual hot-swap controllers/power sequencers 12 ______________________________________________________________________________________ internal signal v gate_ v out_ pgood discharge rate depends on output loading mon_ glitch filter, 20 s uv/ov condition figure 6. power-down when an undervoltage/overvoltage fault occurs (max5906/max5907) internal signal uv/ov condition v gate_ v out_ pgood v gate_ and v out_ stay on mon_ glitch filter, 20 s figure 7. fault report when an undervoltage/overvoltage fault occurs (max5908/max5909) timing diagrams (continued)
max5904?ax5909 low-voltage, dual hot-swap controllers/power sequencers ______________________________________________________________________________________ 13 t pgdly t d,uvlo v uvlo v in_ v gate_ v out_ internal signal internal signal pgood t start figure 8. power-up with undervoltage lockout delay (v on = 2.7v, the other v in_ is below v uvlo ) timing diagrams (continued)
max5904?ax5909 put voltage fault on either mon1 or mon2, the fault is latched and both external mosfet gates are dis- charged at 3ma. when the max5908/max5909 detect an output voltage fault the external mosfet gates are not affected. the max5908/max5909 pgood goes high impedance when the output voltage fault is removed. the voltage monitors do not react to output glitches of less than 20s. a capacitor from mon_ to gnd increases the effective glitch filter time. connect mon1 to in1 and mon2 to in2 to disable the output voltage monitors. status output (pgood) the status output is an open-drain output that pulls low in response to one of the following conditions: forced off (on < 0.8v) overcurrent fault output voltage fault pgood goes high impedance 0.75ms after the device enters normal operation and no faults are present ( table 1 ). applications information component selection n-channel mosfet select the external mosfets according to the applica- tion s current levels. table 2 lists some recommended components. the mosfet s on-resistance (r ds(on) ) should be chosen low enough to have a minimum volt- age drop at full load to limit the mosfet power dissipa- tion. high r ds(on) causes output ripple if there is a pulsating load. determine the device power rating to accommodate a short-circuit condition on the board at startup and when the device is in automatic-retry mode (see mosfet thermal considerations ). using the MAX5905/max5907/max5909 in latched mode allows the use of mosfets with lower power rat- ings. a mosfet typically withstands single-shot pulses with higher dissipation than the specified package rat- ing. table 3 lists some recommended manufacturers and components. sense resistor the slow-comparator threshold voltage is set at 25mv for the max5904/MAX5905 and is adjustable from 25mv to 100mv for the max5906 max5909. select a sense resistor that causes a drop equal to the slow- comparator threshold voltage at a current level above the maximum normal operating current. typically, set the overload current at 1.2 to 1.5 times the nominal load current. the fast-comparator threshold is four times the slow-comparator threshold in normal operating mode. choose the sense resistor power rating to be greater than (i overload ) 2 x v sc,th . slow-comparator threshold, r lim the slow-comparator threshold voltage of the max5904/MAX5905 is fixed at 25mv and adjustable from 25mv to 100mv for the max5906 max5909. the adjustable slow-comparator threshold of the max5906 max5909 allows designers to fine-tune the current-limit threshold for use with standard value sense resistors. low slow-comparator thresholds allow for increased efficiency by reducing the power dissipat- ed by the sense resistor. furthermore, the low 25mv slow-comparator threshold is beneficial when operating with supply rails down to 1v because it allows a small percentage of the overall output voltage to be used for current sensing. the variablespeed/bilevel fault pro- tection feature offers inherent system immunity against load transients and noise. this allows the slow-com- parator threshold to be set close to the maximum nor- mal operating level without experiencing nuisance low-voltage, dual hot-swap controllers/power sequencers 14 ______________________________________________________________________________________ table 1. status output truth table device in uvlo delay period device in startup period on overcurrent fault over/under- voltage fault part in retry-timeout period or latched off pgood yes x x x x x low x yes x x x x low x x low x x x low x x x yes x x low x x x x yes x low x x x x x yes low no no high no no no high-z x = don? care
faults. typically, set the overload current at 1.2 to 1.5 times the nominal load current. to adjust the slow-com- parator threshold calculate r lim as follows: where v th is the desired slow-comparator threshold voltage. setting the startup period, r tim the startup period (t start ) of the max5904/MAX5905 is fixed at 9ms, and adjustable from 0.4ms to 50ms for the max5906 max5909. the adjustable startup period of the max5906 max5909 systems can be customized for mosfet gate capacitance and board capacitance (c board ). the startup period is adjusted with the resis- tance connected from tim to gnd (r tim ). r tim must be between 4k ? and 500k ? . the max5906 max5909 start- up period has a default value of 9ms when tim is left floating. calculate r tim with the following equation: where t start is the desired startup period. there are two ways of completing the startup sequence. case a describes a startup sequence that slowly turns on the mosfets by limiting the gate charge. case b uses the current-limiting feature and turns on the mosfets as fast as possible while still preventing a high inrush current. the output voltage ramp-up time (t on ) is determined by the longer of the two timings, case a and case b. set the max5906 max5909 startup timer t start to be longer than t on to guarantee enough time for the output voltage to settle. case a: slow turn-on (without current limit) there are two ways to turn on the mosfets without reaching the fast-comparator current limit: if the board capacitance (c board ) is small, the inrush current is low. if the gate capacitance is high, the mosfets turn on slowly. in both cases, the turn-on time is determined only by the charge required to enhance the mosfet. the small gate-charging current of 100a effectively limits the out- put voltage dv/dt. connecting an external capacitor between gate and gnd extends turn-on time. the time required to charge/discharge a mosfet is as follows: where: c gate is the external gate to ground capacitance (figure 4) ? v gate is the change in gate voltage q gate is the mosfet total gate charge i gate is the gate charging/discharging current in this case, the inrush current depends on the mosfet gate-to-drain capacitance (c rss ) plus any additional capacitance from gate to gnd (c gate ), and on any load current (i load ) present during the startup period. t cvq i gate gate gate gate = ? + r t pf tim start = 128 800 r vmv a lim th = ? 25 025 . max5904?ax5909 low-voltage, dual hot-swap controllers/power sequencers ______________________________________________________________________________________ 15 component manufacturer phone website dale-vishay 402-564-3131 www.vishay.com sense resistors irc 704-264-8861 www.irctt.com international rectifier 310-233-3331 www.irf.com fairchild 888-522-5372 www.fairchildsemi.com mosfets motorola 602-244-3576 www.mot-sps.com/ppd part number manufacturer description irf7413 11m ? , 8 so, 30v irf7401 22m ? , 8 so, 20v irl3502s international rectifier 6m ? , d2pak, 20v mmsf3300 20m ? , 8 so, 30v mmsf5n02h 30m ? , 8 so, 20v mtb60n05h motorola 14m ? , d2pak, 50v fds6670a 10m ? , 8so, 30v nds8426a 13.5m ? , 8 so, 20v fdb8030l fairchild 4.5m ? , d2pak, 30v table 2. recommended n-channel mosfets table 3. component manufacturers
max5904?ax5909 example: charging and discharging times using the fairchild fdb7030l mosfet if v in1 = 5v then gate1 charges up to 10.4v (v in1 + v drive ), therefore ? v gate = 10.4v. the manufacturer s data sheet specifies that the fdb7030l has approxi- mately 60nc of gate charge and c rss = 600pf. the max5904 max5909 have a 100a gate-charging cur- rent and a 100a weak discharging current or 3ma strong discharging current. c board = 6f and the load does not draw any current during the startup period. with no gate capacitor the inrush current, charge, and discharge times are: with a 22nf gate capacitor the inrush current, charge, and discharge times are: case b: fast turn-on (with current limit) in applications where the board capacitance (c board ) is high, the inrush current causes a voltage drop across r sense that exceeds the startup fast-comparator threshold. the fast comparator regulates the voltage across the sense resistor to v su,th . this effectively regulates the inrush current during startup. in this case, the current charging c board can be considered con- stant and the turn-on time is: the maximum inrush current in this case is: figures 2 8 show the waveforms and timing diagrams for a startup transient with current regulation. (see typical operating characteristics. ) when operating under this condition, an external gate capacitor is not required. on comparator the on comparator controls the on/off function of the max5904 max5909. on is the input to a precision three-level voltage comparator that allows individual control over channel 1 and channel 2. drive on high (> 2.025v) to enable channel 1 and channel 2. pull on low (<0.4v) to disable both channels. to enable chan- nel 1 only, v on must be between the channel 1 on threshold (0.825v) and the channel 2 on threshold (2.025v). the device can be turned off slowly, reducing inductive kickback, by forcing on between 0.4v and 0.825v until the gates are discharged. the on com- parator is ideal for power sequencing ( figure 11 ). uncommitted comparator the max5906 max5909 feature an uncommitted com- parator that increases system flexibility. this compara- tor can be used for voltage monitoring, or for generating a power-on reset signal for on-card micro- processors ( figure 12 ). the uncommitted comparator output (outc) is open drain and is pulled low when the comparator input volt- age (v inc+ ) is below its threshold voltage (1.236v). outc is high impedance when v inc+ is greater than 1.236v. using the max5904?ax5909 on the backplane using the max5904 max5909 on the backplane allows multiple cards with different input capacitance to be inserted into the same slot even if the card does not have on-board hot-swap protection. the startup period can be triggered if in is connected to on through a trace on the card ( figure 13 ). input transients the voltage at in1 or in2 must be above the uvlo dur- ing inrush and fault conditions. when a short-circuit condition occurs on the board, the fast comparator trips i v r inrush su th sense = , t cvr v on board in sense su th = , i f pf nf ama t nf v nc a ms t nf v nc a ms t nf v nc ma ms inrush charge discharge slow discharge fast = + += = + = = + = = + = 6 600 22 100 0 26 5 22 10 4 60 100 289 22 10 4 60 100 289 22 10 4 60 3 0 096 . . . . . . . _ _ i f pf aa t vnc a ms t vnc a ms t vnc ma ms inrush charge discharge slow discharge fast = + += = + = = + = = + = 6 600 0 100 0 1 0104 60 100 06 0104 60 100 06 0104 60 3 002 . . . . . . _ _ i c cc ii inrush board rss gate gate load = + + low-voltage, dual hot-swap controllers/power sequencers 16 ______________________________________________________________________________________
causing the external mosfet gates to be discharged at 3ma. the main system power supply must be able to sustain a temporary fault current, without dropping below the uvlo threshold of 2.4v, until the external mosfet is completely off. if the main system power supply collapses below uvlo, the max5904 max5909 will force the device to restart once the supply has recovered. the mosfet is turned off in a very short time resulting in a high di/dt. the backplane delivering the power to the external card must have low induc- tance to minimize voltage transients caused by this high di/dt. mosfet thermal considerations during normal operation, the external mosfets dissi- pate little power. the mosfet r ds(on) is low when the mosfet is fully enhanced. the power dissipated in normal operation is p d = i load 2 x r ds(on) . the most power dissipation occurs during the turn-on and turn- off transients when the mosfets are in their linear regions. take into consideration the worst-case sce- nario of a continuous short-circuit fault, consider these two cases: 1) the single turn-on with the device latched after a fault (MAX5905/max5907/max5909) 2) the continuous automatic retry after a fault (max5904/max5906/max5908) mosfet manufacturers typically include the package thermal resistance from junction to ambient (r ja ) and thermal resistance from junction to case (r jc ) which determine the startup time and the retry duty cycle (d = t start / t retry ). calculate the required transient ther- mal resistance with the following equation: where i start = v su,th / r sense layout considerations to take full tracking advantage of the switch response time to an output fault condition, it is important to keep all traces as short as possible and to maximize the high-current trace dimensions to reduce the effect of undesirable parasitic inductance. place the max5904 max5909 close to the card s connector. use a ground plane to minimize impedance and inductance. minimize the current-sense resistor trace length (<10mm), and ensure accurate current sensing with kelvin connections ( figure 14 ). when the output is short circuited, the voltage drop across the external mosfet becomes large. hence, the power dissipation across the switch increases, as does the die temperature. an efficient way to achieve good power dissipation on a surface-mount package is to lay out two copper pads directly under the mosfet package on both sides of the board. connect the two pads to the ground plane through vias, and use enlarged copper mounting pads on the top side of the board. see max5908 ev kit. z tt vi ja max jmax a in start () ? max5904?ax5909 low-voltage, dual hot-swap controllers/power sequencers ______________________________________________________________________________________ 17 sense voltage (v in - v sense ) turn-off time v sc,th v fc,th (4 x v sc,th ) 3ms 110 s 260ns slow comparator fast comparator figure 9. variablespeed/bilevel response gate sense gnd on r sense v out c gate c board v in in r pullup pgood max5906 max5907 max5908 max5909 figure 10. operating with an external gate capacitor
max5904?ax5909 chip information transistor count: 3230 process: bicmos low-voltage, dual hot-swap controllers/power sequencers 18 ______________________________________________________________________________________ in1 gate1 in2 gate2 q1 r sense1 sense1 r sense2 sense2 q2 c board2 out1 c board1 out2 v 1 c 1 r 1 v en v 2 on off gnd max5904 MAX5905 on gnd v on1, th v on2, th t delay v en t 1 = -r 1 c 1 ln ( ) v en - v on1, th v en v on v 1 v 2 t 0 t 1 t 2 t 2 = -r 1 c 1 ln ( ) v en - v on2, th v en t delay = -r 1 c 1 ln ( ) v en - v on1, th v en - v on2, th figure 11. power sequencing: channel 2 turns on t delay after channel 1
max5904?ax5909 low-voltage, dual hot-swap controllers/power sequencers ______________________________________________________________________________________ 19 part output undervoltage/overvoltage protection/monitor fault management max5904esa/max5904usa auto-retry MAX5905esa/MAX5905usa latched max5906eee/max5906uee protection auto-retry max5907eee/max5907uee protection latched max5908eee/max5908uee monitor auto-retry max5909eee/max5909uee monitor latched selector guide outc inc+ reset p in gate v in sense max5906?ax5909 figure 12. power-on reset on in gate v in v out sense max590_ c board backplane removable card with no hot-insertion projection figure 13. using the max5904?ax5909 on a backplane sense resistor high-current path max590_ figure 14. kelvin connection for the current-sense resistors 16 15 14 13 12 11 10 9 1 2 3 4 5 6 7 8 pgood outc inc+ in2 sense2 gate2 on lim2 mon2 top view max5906 max5907 max5908 max5909 qsop tim in1 gnd sense1 gate1 lim1 mon1 pin configurations (continued)
max5904?ax5909 low-voltage, dual hot-swap controllers/power sequencers 20 ______________________________________________________________________________________ in1 gate1 in2 gate2 q1 r sense1 sense1 r sense2 sense2 q2 c board2 out1 c board1 out2 v 1 v 2 on gnd backplane removable card max5904 MAX5905 on gnd 0.1 f 0.1 f in1 gate1 in2 gate2 q1 r sense1 sense1 r sense2 sense2 q2 c board2 out1 c board1 out2 v 1 v 2 on mon1 mon2 outc inc+ stat gnd backplane removable card uncommitted comparator * * * * *optional on pgood lim1 lim2 tim gnd * * * max5906 max5907 max5908 max5909 0.1 f 0.1 f typical operating circuits
max5904?ax5909 low-voltage, dual hot-swap controllers/power sequencers ______________________________________________________________________________________ 21 soicn .eps package outline, .150" soic 1 1 21-0041 b rev. document control no. approval proprietary information title: top view front view max 0.010 0.069 0.019 0.157 0.010 inches 0.150 0.007 e c dim 0.014 0.004 b a1 min 0.053 a 0.19 3.80 4.00 0.25 millimeters 0.10 0.35 1.35 min 0.49 0.25 max 1.75 0.050 0.016 l 0.40 1.27 0.394 0.386 d d min dim d inches max 9.80 10.00 millimeters min max 16 ac 0.337 0.344 ab 8.75 8.55 14 0.189 0.197 aa 5.00 4.80 8 n ms012 n side view h 0.244 0.228 5.80 6.20 e 0.050 bsc 1.27 bsc c h e e b a1 a d 0-8 l 1 variations: package information (the package drawing(s) in this data sheet may not reflect the most current specifications. for the latest package outline info rmation, go to www.maxim-ic.com/packages .)
max5904?ax5909 low-voltage, dual hot-swap controllers/power sequencers maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a maxim product. no circu it 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 ? 2003 maxim integrated products printed usa is a registered trademark of maxim integrated products. qsop.eps package information (continued) (the package drawing(s) in this data sheet may not reflect the most current specifications. for the latest package outline info rmation, go to www.maxim-ic.com/packages .)

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