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general description the MAX15068 offers oring function and hot-swap features for two input-supply-rail applications requiring the safe insertion and removal of circuit line cards from a live backplane. the device integrates dual oring mosfet controllers, a single hot-swap controller, electronic circuit- breaker protection, and power monitoring in a single package. the device is designed to operate from 3.7v to 18v supply voltages. the device regulates the forward voltage drop across the oring mosfets to ensure smooth current transfer from one supply to the other without oscillation. the oring mosfet turns on quickly to reduce the load voltage droop during supply switchover. if the input supply fails or is short - ed, a fast turn-off minimizes reverse-current transients. the device implements a foldback current limit during hot- swap startup in order to control inrush current, thereby lowering di/dt and keeping the operation of the hot-swap mosfet under safe operating area (soa). an internal 70ms timer starts counting when the device enters the hot-swap startup phase. after the hot-swap startup cycle is completed, on-chip comparators provide active current- limit protection against short-circuit and overcurrent faults. the load is disconnected from the input quickly in the event of a fault condition. the device provides current monitoring from 3a to 10a (v in = 12v, t a = +25c with r sense = 3m) with 0.6% accuracy. a voltage proportional to the input current delivered to the system could be read directly at the ipmon pin. the device is factory-calibrated to deliver accurate overcurrent protection with 5% accuracy. during an overcurrent-fault condition, the device enters an autoretry mode. the device features an adjustable slew-rate control during startup. additional features include power-good and fault-indicator outputs. the MAX15068 is available in a 20-pin, (4mm x 5mm) tqfn package and is specified from a -40c to +125c operating temperature range. features and benefts 3.7v to 18v operating voltage range (oring and hot swap) 4.8v to 18v operating voltage range (current monitor) seamless power transition of redundant supplies controls n-channel mosfets < 0.5s turn-on and reverse turn-off time current monitoring (0.6% accuracy typ) programmable slew-rate control adjustable current-limit fault delay programmable circuit-breaker current threshold inrush current regulated at startup with programmable soa control programmable undervoltage lockout small (4mm x 5mm) tqfn package applications baseband station redundant power supplies supply holdup computer systems and servers telecom networks storage bridge bay ordering information appears at end of data sheet. for related parts and recommended products to use with this part, refer to www.maximintegrated.com/MAX15068.related . 19-6872; rev 0; 12/13 evaluation kit available MAX15068 dual oring, single hot-swap controller with accurate current monitoring
in1, in2 to gnd ....................................................... -1v to +24v pg , en , fault , csn to gnd .............................. -0.3v to +24v csp to gnd ............................................. -0.3v to (v in_ + 0.6v) v s to gnd ............................................................... -0.3v to +6v on, pc , ipmon, cb, cdly to gnd .......... -0.3v to (v s + 0.3v) csp to csn ......................................................... -0.3v to +0.3v out to gnd .......................................................... -0.3v to +24v gate to gnd ........................................................ -0.3v to +36v gate to out ........................................................ -0.3v to +20v cp1 to gnd .......................................................... -0.3v to +36v cp1 to in1 ............................................................. -0.3v to +14v cp2 to gnd .......................................................... -0.3v to +36v cp2 to in2 ............................................................. -0.3v to +14v og1 ............................................. (v in1 - 0.3v) to (v cp1 + 0.3v) og2 ............................................. (v in2 - 0.3v) to (v cp2 + 0.3v) current into en , pg , fault .............................................. 20ma continuous power dissipation (t a = +70 c) 20-tqfn (derate 30mw/oc above +70 c) ................... 2400mw operating temperature range ......................... -40 c to +125 c junction temperature ...................................................... +150 c storage temperature range ............................ -65 c to +150 c lead temperature (soldering, 10s) ................................. +300 c soldering temperature (reflow) ....................................... +260 c tqfn junction-to-ambient thermal resistance ( ja ) ....... 33.5c/w (note 1) (v in1 = v in2 = 12v, c in1 = c in2 = c vs = 1f, t a = -40 c to +125 c. typical values are at t a = +25 c, unless otherwise noted.) (note 2) parameter symbol conditions min typ max units supply voltage input supply voltage v in hot swap and oring 3.7 18 v current monitor 4.8 18 input supply current i in 4 ma internal ldo output voltage v s 4.8 5 5.25 v v s undervoltage lockout v uvlo v s rising 2.5 2.65 2.8 v v s undervoltage-lockout hysteresis v uvlo_hys 0.07 v csp undervoltage lockout v csp_uvlo v csp rising 2.4 2.49 2.58 v v csp falling 2.25 2.35 2.42 oring oring mosfet forward regulation voltage (v in_ - v csp ) v fwd_reg 7.5 10 12.5 mv oring mosfet reverse bias turn-off voltage v rev_off v in_ - v csp , v csp rising (v csp > v in_ ), v og_ goes low -12.5 -10 -7.5 mv oring mosfet reverse bias turn-on voltage v rev_on v in_ - v csp , v csp falling (v in_ > v csp_ ), v og_ goes to forward regulation +8.5 +10 +13.5 mv oring mosfet reverse bias hysteresis voltage v rev_hys v rev_off - v rev_on 20 mv maxim integrated 2 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.maximintegrated.com/thermal-tutorial . absolute maximum ratings stresses beyond those listed under absolute maximum ratings may cause permanent damage to the device. these are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. exposure to ab solute maximum rating conditions for extended periods may affect device reliability. package thermal characteristics electrical characteristics MAX15068 dual oring, single hot-swap controller with accurate current monitoring www.maximintegrated.com
(v in1 = v in2 = 12v, c in1 = c in2 = c vs = 1f, t a = -40 c to +125 c. typical values are at t a = +25 c, unless otherwise noted.) (note 2) parameter symbol conditions min typ max units turn-off switch resistance r ds_off v in_ - v csp = -50mv, i = 50ma 0.8 ? turn-on switch resistance r ds_on v in_ - v csp_ = 120mv, i = 70ma 2 ? oring mosfet gate drive (v og_ - v in_ ) v og_ 3.75v < v in_ < 18v 6 11 12 v oring mosfet fast turn-on threshold v fwd_on v in_ - v csp rising 80 mv oring mosfet fast turn-off v fwd_off v in_ - v csp falling, v og_ goes to forward regulation 40 mv oring mosfet turn-on delay t on_og_ c gate = 10nf, v in_ - v csp = +0.05v 150 ns oring mosfet turn-off delay t off_og_ c gate = 10nf, v in_ - v csp = -0.05v, v og_ = 0.1 x (v cp_ - v in_ ) 200 300 ns pc to og2 delay t lh_dly v pc falling edge to v og2 going high 40 65 s hot swap circuit-breaker accuracy v cb_th v csp - v csn v cb = 0v 32.9 35 37.1 mv v cb = hi-z 47.5 50 52.5 v cb = v s 61.1 65 68.9 active current-limit sense voltage v acl 1.3 x v cb_th mv fast comparator threshold v fc_th v csp - v csn 3 x v cb_th mv fast comparator response time t fc_dly v csp - v csn = 300mv, c gate = 10nf (note 3) 200 ns gate off delay t off_gate v en high to v gate low 20 40 s v on low to v gate low 10 20 gate propagation delay t on_gate_pd v on = step 0.8v to 2v 10 20 s gate drive voltage (v gate - v out ) v gate 3.7v < v in_ < 18v 6 11 v gate pullup current i gate_on v gate - v out = 0v -13 -10 -7 a gate pulldown current (timeout) i gate_off v out = 12v, v gate = v out + 5v 350 500 650 a gate fast pulldown current i gate_fast_ off v out = 12v, v gate = v out + 5v 75 200 260 ma hot-swap foldback minimum cb voltage v cb_fbmax (v csp - v csn ) = 12v 3 8.33 15 % v cb_th minimum fb voltage v fbmin v csp - v out, at v cb = v cb_fbmax 1 2 3.2 v maxim integrated 3 electrical characteristics (continued) MAX15068 dual oring, single hot-swap controller with accurate current monitoring www.maximintegrated.com
(v in1 = v in2 = 12v, c in1 = c in2 = c vs = 1f, t a = -40 c to +125 c. typical values are at t a = +25 c, unless otherwise noted.) (note 2) parameter symbol conditions min typ max units maximum fb voltage v fbmax v csp - v out , at v cb = v cb_th 9 10 11 v current-sensing input csp input current i csp v csp = 12v 0.5 1.0 ma csn input current i csn v csn = 12v 100 200 400 a cdly cdly upper threshold v cdly_u v cdly rising 1.1 1.2 1.3 v cdly lower threshold hysteresis v cdly_l v cdly falling 0.2 v cdly pullup current i cdly_up -132 -100 -70 a cdly pulldown current i cdly_down 1.2 2 2.8 a cdly ratio i cdly_ratio 1.4 2 3.2 % power-good ( pg ) pg threshold out v pg _out v gate > (5v + v out ) 0.9 x v csp v pg threshold gate v pg _gate v gate - v out 4.2 v pg detection timeout t pg _startup 55 70 85 ms pg assertion delay t pg _delay 13 16 19 ms outputs ( fault , pg ) fault , pg output voltage low v ol i pg = i fault = 1ma 0.4 v fault , pg output voltage high v oh i pg = i fault = 1a v s - 1 v s - 0.6 v fault , pg leakage current i oh v pg = v fault = 18v -1 +20 a fault , pg pullup current i pu v pg = v fault = 1.5v -13 -10 -7 a inputs on, pc , en turn-on threshold v on_th v on , v pc , v en rising 1.1 1.22 1.32 v on, pc , en turn-on threshold hysteresis v on_hys v on , v pc , v en falling 70 123 180 mv on fault reset threshold voltage v on_reset v on falling 0.5 0.6 0.7 v on, pc input leakage current i leak v on , v pc = 0 to 2.5v -1 +1 a on, pc clamp voltage i sink = 1a 3 v on, pc clamp sink v on , v pc = 5v 350 a en pullup current i pu v en = 0v -13 -10 -7 a cb three-state input cb input low current i in_low v cb = 0.4v -75 a cb input high current i in_high v cb = v s - 0.2v +75 a maxim integrated 4 electrical characteristics (continued) MAX15068 dual oring, single hot-swap controller with accurate current monitoring www.maximintegrated.com
(v in1 = v in2 = 12v, c in1 = c in2 = c vs = 1f, t a = -40 c to +125 c. typical values are at t a = +25 c, unless otherwise noted.) (note 2) parameter symbol conditions min typ max units cb input open-current voltage v cb_open force 4a into unconnected cb pin; then measure voltage on the cb pin 1.0 v s - 1 v cb low voltage v il v cb rising 0.4 v cb high voltage v ih v cb falling, relative to v s v s - 0.2 v current monitoring current monitor vs. undervoltage lockout i mon_uvlo v s rising 4.1 4.16 4.23 v hysteresis 0.1 imon offset (note 3) i mon_os v csp = 12v t a = +25c -80 +80 v t a = -40c to +85c -200 +200 t a = -40c to +125c -240 -240 v csp = 4.8v to 18v t a = -40c to +125c -300 +300 imon gain (note 3) g im v csp = 12v t a = +25c 2.991 3.009 ms t a = -40c to +125c 2.9595 3.0405 v csp = 4.8v to 18v t a = -40c to +125c 2.955 3.045 current monitoring total accuracy (note 4) i mon_ accuracy v csp = 12v, r sense = 3m?, i load = 1a, (v csp - v csn) = 3mv, t a = +25c, i mon_accuracy = ((i imon - 9a)/9a) x 100 -3 +3 % v csp = 12v, r sense = 3m?, i load = 5a, (v csp - v csn) = 15mv, t a = +25c, i mon_accuracy = ((i imon - 45a)/45a) x 100 -0.9 +0.9 v csp = 12v, r sense = 3m?, i load = 10a, (v csp - v csn) = 30mv, t a = +25c, i mon_accuracy = ((i imon - 90a)/90a) x 100 -0.6 +0.6 cmrr (note 5) i mon_cmrr v csp = 4.8v to 18v 102 db input voltage range (v csp - v csn ) max v csp = 4.8v to 18v, -40c t a +125c 30 mv output voltage range vimon max v csp = 4.8v to 18v, -40c t a +125c 1.8 v imon voltage clamp v imon_clmp v csp - v csn 36mv, v csp = 4.8v to 18v, -40c t a +125c 2.25 2.4 2.5 v note 2: all devices are 100% production tested at t a = +25c. limits over temperature are guaranteed by design. note 3: gain and offset are defined as imon 1 = imon with vi 1 = (v csp - v csn ) = 3mv, imon 2 = imon with vi 2 = (v csp - v csn ) = 30mv, g im = (imon 2 - imon 1 )/(vi 2 - vi 1 ), i mon_os = imon 1 - g im x vi 1 . note 4: accuracy over the entire operating range can be determined combining the specified value of the related offset and gain in the range. note 5: cmrr is calculated as: i ref = imon with v csp - v csn = 3mv at v ref = v csp = 12v icm = imon with v csp - v csn = 3mv at 4.8v < v csp < 18v cmrr = 20 x log(abs((v ref - v csp )/(i ref - icm)) x g im ) where g im is the differential gain defined in the ec table. maxim integrated 5 electrical characteristics (continued) MAX15068 dual oring, single hot-swap controller with accurate current monitoring www.maximintegrated.com
(v in1 = v in2 = 12v, c in1 = c in2 = c vs = 1f, r sense = 3m, unless otherwise noted.) 0 1 2 3 4 5 6 0 2 4 6 8 10 v s (v) i load (ma) v s load regulation v in_ = 12v or 18v v in_ = 5v v in_ = 3.7v toc02 0 2 4 6 8 10 12 0 20 40 60 80 100 120 140 v cp_ - v in_ (v) i icp_ (a) charge - pump voltage vs. current toc03 v in_ = 3.7v v in_ = 12v v in_ = 18v 0 2 4 6 8 10 12 14 3 6 9 12 15 18 v cp_ (v) v in_ (v) charge - pump voltage vs. input voltage toc04 20 40 60 80 -40 -15 10 35 60 85 110 circuit - breaker trip voltage (mv) temperature (oc) circuit - breaker trip voltage vs. temperature toc07 125 cb = gnd cb = v s cb = hi - z 40 60 80 100 -40 -15 10 35 60 85 110 active current - limit sense voltage (mv) temperature (oc) active current - limit sense voltage vs. temperature toc08 125 cb = v s cb = gnd cb = hi - z 0 2 4 6 8 10 12 0 20 40 60 80 100 120 140 v cp_ - v in_ (v) i icp_ (a) oring gate voltage vs. current toc05 v in_ = 3.7v v in_ = 18v v in_ = 12v 0 3 6 9 12 15 0 5 10 15 v gate - v out (v) i gate (a) hot - swap mosfet gate voltage vs. current v in_ = 3.7v v in_ = 12v or 18v v in_ = 5v v out = v in_ toc06 0 2 4 6 0 3 6 9 12 15 18 i in_ (ma) v in_ (v) in_ supply current vs. voltage i in2 i in1 toc01 maxim integrated 6 typical operating characteristics MAX15068 dual oring, single hot-swap controller with accurate current monitoring www.maximintegrated.com
(v in1 = v in2 = 12v, c in1 = c in2 = c vs = 1f, r sense = 3m, unless otherwise noted.) -20 -15 -10 -5 0 5 0 2 4 6 8 10 12 imon output accuracy (%) current (a) imon output accuracy (t a = +85oc) toc15 v in_ = 4.5v v in_ = 12v v in_ = 18v v in_ = 4.5v v in_ = 12v or 18v -20 -15 -10 -5 0 5 0 2 4 6 8 10 12 imon output accuracy (%) current (a) imon output accuracy (t a = +125oc) toc16 v in_ = 4.5v v in_ = 18v v in_ = 12v v in_ = 4.5v v in_ = 12v or 18v 0.01 0.1 1 10 100 0 50 100 150 200 250 300 active current - limit delay (s) sense voltage (v csp - v csn ) (mv) active current - limit delay vs. sense voltage toc09 cb = v s cb = gnd cb = hi - z 0 10 20 30 40 50 0 2 4 6 8 10 output low voltage (mv) current (ma) pg, fault output low voltage vs. current toc10 40 60 80 100 120 140 -40 -15 10 35 60 85 110 cdly pullup current (a) temperature (oc) cdly pullup current vs. temperature toc11 125 0 5 10 15 20 -40 -15 10 35 60 85 110 gate pullup current (a) temperature (oc) gate pullup current vs. temperature toc12 125 -20 -15 -10 -5 0 5 0 2 4 6 8 10 12 imon output accuracy (%) current (a) imon output accuracy (t a = - 40oc) toc13 v in_ = 4.5v v in_ = 12v v in_ = 18v v in_ = 4.5v v in_ = 18v v in_ = 12v -20 -15 -10 -5 0 5 0 2 4 6 8 10 12 imon output accuracy (%) current (a) imon output accuracy (t a = +25oc) toc14 v in_ = 4.5v v in_ = 12v v in_ = 18v v in_ = 4.5v v in_ = 12v or 18v maxim integrated 7 typical operating characteristics (continued) MAX15068 dual oring, single hot-swap controller with accurate current monitoring www.maximintegrated.com
(v in1 = v in2 = 12v, c in1 = c in2 = c vs = 1f, r sense = 3m, unless otherwise noted.) out short - circuit response 10v/div 20v/div 10v/div toc23 40s/div v in1 v out v gate i in1 10a/div autorety waveform 10v/div 20v/div 10v/div toc24 200ms/div v in1 v out v gate i out 20a/div startup waveform (v in = 3.7v) 2v/div 5v/div 5v/div toc17 40ms/div v in1 v og1 v gate startup waveform (v in = 12v) 5v/div 5v/div 10v/div toc18 40ms/div v in1 v og1 v gate startup waveform (v in = 18v) 10v/div 10v/div 10v/div toc19 40ms/div v in1 v og1 v gate overcurrent - fault waveform (cb = gnd) 10v/div 20v/div 10v/div toc20 200s/div v in1 v gate v out i out 20a/div overcurrent - fault waveform (cb = hi -z) 10v/div 20v/div 10v/div toc21 200s/div v in1 v gate v out i out 20a/div overcurrent - fault waveform (cb = v s ) 10v/div 20v/div 10v/div toc22 200s/div v in1 v gate v out i out 20a/div maxim integrated 8 typical operating characteristics (continued) MAX15068 dual oring, single hot-swap controller with accurate current monitoring www.maximintegrated.com
pin name function 1 csn input current sense negative input 2 csp input current sense positive input 3 in1 positive supply 1 input and mosfet gate drive return 4 v s internal regulator output. bypass v s to gnd with a 1f capacitor. 5 gnd ground 6 in2 positive supply 2 input and mosfet gate drive return 7 og2 oring mosfet 2 gate control output. connect this pin to the gate of an external n-channel mosfet for ideal diode control. the gate voltage is limited to approximately 11v above and a diode voltage below in2. during fast turn-on, a 1a pullup switch charges og2 from cp2. during fast turn-off, a 3a pulldown switch discharges og2 to in2. 8 cp2 charge pump 2 output. connect a capacitor from cp2 to in2 pin. the value of this capacitor should be approximately 10x the gate capacitance (ciss) of the external mosfet for oring diode control. the charge stored on this capacitor is used to pull up the gate during a fast turn-on. 9 ipmon analog current monitor output signal. connect a resistor from ipmon to gnd to set the monitor gain. tqfn ( 4 mm 5 mm ) top view max 15068 ep + og 1 cp 1 gate out 7 8 9 10 1 csn 2 csp 3 in 1 4 v s 5 gnd 6 in 2 16 cb 15 on 14 en 13 cdly 12 pc 11 fault og 2 cp 2 ipmon pg 20 19 18 17 maxim integrated 9 pin confguration pin description MAX15068 dual oring, single hot-swap controller with accurate current monitoring www.maximintegrated.com
pin name function 10 pg power status output. open-drain output that is normally pulled high by a 10a current source to a diode below v s . pg can be pulled above v s using an external pullup. pg pulls low when the mosfet gate drive between gate and out exceeds the gate-to-source volt age of 4.2v and v out is greater than 90% of v csp . leave pg unconnected if unused. 11 fault fault status output. open-drain output that is normally pulled high by a 10a current source to a diode below v s . fault can be pulled above v s using an external pullup. fault pulls low when the circuit breaker is tripped after an overcurrent fault timeout. leave fault unconnected if unused. 12 pc priority control input. when low, it enables the external ideal diode mosfet in the in2 supply path and a high turns it off. connect pc to an external resistive divider from in1 to make in1 the higher priority input supply when in1 and in2 are equal. connect pc to gnd if not used. 13 cdly timer capacitor terminal. connect a capacitor between cdly and gnd to set 12ms/f duration for current limit before the external hot-swap mosfet is turned off. the duration of the off-time is 600ms/ f, resulting in a 2% duty cycle. 14 en enable input. connect en to gnd to enable hot-swap control. if en is pulled high, the hot-swap mosfet is not allowed to turn on. a 10a current source pulls up en to a diode below v s . upon en going low when on is high, an internal timer provides a 100ms startup delay for debounce, after which the fault is cleared. 15 on on control input. when above 1.2v, it turns on the external hot-swap mosfet and when below 1.1v, it turns it off. connect on to an external resistive divider from csp to monitor the supply undervoltage condition. pulling voltage of on pin below 0.6v resets the electronic circuit breaker. 16 cb current-limit threshold setting. connect the cb pin to v s , gnd, or leave cb unconnected to set the circuit-breaker threshold. see table 1 for details. 17 out load output. connect out to the source of the external hot-swap mosfet. 18 gate hot-swap mosfet gate drive output. connect this pin to the gate of the external n-channel mosfet for hot-swap control. an internal 10a current source charges the mosfet gate. an internal clamp limits the gate voltage to 11v above out and a diode voltage below out. during turn-off, a 500a pulldown current discharges gate to ground. during an output short to ground, a fast 200ma pulldown current discharges gate to out. 19 cp1 charge pump 1 output. connect a capacitor from cp1 to in1 pin. the value of this capacitor should be 10x or greater than the gate capacitance of the external mosfet for ideal diode control. the charge stored on this capacitor is used to pull up the gate during a fast turn-on. 20 og1 oring mosfet 1 gate control output. connect og1 to the gate of an external n-channel mosfet for ideal diode control. the gate voltage is set to approximately 11v above and a diode voltage below in1. during fast turn-on, a 1a pullup switch charges og1 from cp1. during fast turn-off, a 3a pulldown switch discharges og1 to in1. ep exposed pad. connect ep to the ground plane to provide a low thermal resistance path from the ic junction to the pcb. do not use ep as an electrical connection to gnd. maxim integrated 10 pin description (continued) MAX15068 dual oring, single hot-swap controller with accurate current monitoring www.maximintegrated.com
logic control v cb 0.9 x v csp pg gate _ok gate on v s pc MAX15068 - current monitor gate on fault reset en card present cdly gnd gate v s ldo regulator reference generator 1 .2v in1 cp1 + gate driver + charge pump 2 + circuit breaker ipmon out fault overcurrent v s 10 mv 10 a uv2 65mv v cb cb MAX15068 og1 v s v s charge pump 3 10 a cp 2 og2 + - 10mv 2 .49v 1.2v + 0 . 6 v v s 100a 1 . 2 v + 0 . 2 v 10 a 10 a + - + - + - + - 50 mv 35 mv csp csn in 2 charge pump 1 v s + - + - 1 . 3 x v cb uv 1 2 . 65 v 2 a 1 . 2 v 1 . 2 v maxim integrated 11 functional diagram MAX15068 dual oring, single hot-swap controller with accurate current monitoring www.maximintegrated.com
detailed description startup when input voltage is applied to in_, csp comes up to one diode below the higher of in1 or in2. the internal ldo regulator powers v s from the higher of two inputs as well. when both v s and csp reach their respective uvlo thresholds, the internal charge pumps (cp1 or cp2) for the oring controller start operating. an internal time starts when both on is above its threshold and en is below its threshold. after the timer counts 85ms, the oring control (og1 or og2) begins operating. after an - other 15ms have elapsed, the hot-swap control (gate) also starts operating. oring control oring control in startup during a normal power-up, the oring mosfets turn on first. as soon as the internally generated supply, v s , rises above its undervoltage lockout threshold, the inter - nal charge pump is allowed to charge up the cp_ pins. because the ideal diode mosfets are connected in par - allel as a diode-or, the csp pin voltage selects the high - est of the supplies at the in1 and in2 pins. the mosfet associated with the lower input supply voltage is turned off by the corresponding gate drive amplifier. at power-up the cp_ and og_ pin voltages are at the in_ voltage level. cp_ starts ramping up after vs clears its undervoltage lockout level. afterward, og_ ramps up with cp_. the gate drive amplifier monitors the voltage between the in and csp pins and drives the respective og_ pin. if the amplifier senses a forward voltage drop greater than 80mv between in and csp then the og_ pin is pulled to cp to quickly turn on the mosfet. if the amplifier senses a reverse voltage drop greater than 10mv between csp and in_, then the og_pin is pulled to in_ to quickly turn off the mosfet. with the ideal diode mosfets acting as an input supply diode-or, the csp pin voltage rises to the highest of the supplies at the in1 and in2 pins. the stored charge in an external capacitor connected between the cp_ and in_ pins provides the charge needed to quickly turn on and off the ideal diode mosfet. an internal charge pump charges the external capacitors at the cp pins. the og_ pin sources current from the cp_ pin and sinks cur - rent into the in_ and gnd pins. oring mosfet regulation mode when the ideal diode mosfet is turned on, the gate drive amplifier controls og_ to servo the forward voltage drop (v in - v csp ) across the mosfet to 10mv. if the load current causes more than 10mv of voltage drop, across the fet, then the og voltage rises to enhance the mosfet. for large output currents, the mosfets gate is driven fully on and the voltage drop is equal to i load x r ds(on) of the mosfet. hot-swap control hot-swap in startup once the output is enabled, the device provides controlled application of power to the load. the voltage at out begins to rise until the internal selected final maximum current limit is reached, which is programmed through the cb pin ( table 1 ). the low limit is approximately 1/12th of the upper limit as shown in figure 1 . once the power- good threshold is achieved, the normalized hot-swap electronic circuit-breaker (ecb) threshold goes to its full value. an external capacitor connected to the gate pin allows the user to program the slew rate to a value lower than the default. during startup, a foldback current limit is active to protect the external hot-swap mosfet to operate within the soa ( figure 1 ). an internal timer is activated to count for 70ms, which is the maximum time duration for the startup phase. the startup phase is completed when the voltage at out rises above the power-good threshold (0.9 x v csp typical) and hot-swap gate to out voltage exceeds 4.2v even though the 70ms timeout has not yet elapsed. programmable speed circuit-breaker response on hot-swap mosfet the device features an adjustable current limit with circuit-breaker function that protects the external mosfets against short circuits or excessive load current. the voltage across the external sense resistor (r sense ) is monitored by an electronic circuit breaker (ecb) and figure 1. inrush current vs. voltage drop across the hot-swap switch during startup period figure 1 v cb normalize threshold 0 . 6 0 . 5 0 . 4 0 . 3 0 . 2 0 . 1 2 v 10 v 12 v v csn - v out maxim integrated 12 MAX15068 dual oring, single hot-swap controller with accurate current monitoring www.maximintegrated.com
active current limit amplifier (acl). the electronic circuit breaker turns off the hot-swap mosfet with a 500a current from gate to out if the voltage across the sense resistor exceeds v cb_th (ecb) for longer than the fault filter delay configured at the cdly pin. active current limiting begins when the sense voltage exceeds the acl threshold v acl (acl) (which is 1.3x the ecb threshold). the gate of the hot-swap mosfet is brought under control by the acl amplifier and the output current is regulated to maintain the acl threshold across the sense resistor. at this point, the fault filter starts the timeout with a 100a current charging the cdly pin capacitor. if the cdly pin voltage exceeds its threshold (1.2v), the exter - nal mosfet is turned off and the fault pin pulls low. after the hot-swap mosfet turns off, the cdly pin capacitor is discharged with a 2a pulldown current until it reaches 0.2v. this is followed by a cool-off period of 14 timing cycles at the cdly pin. for the autoretry part, the latched fault is cleared automatically at the end of the cool-off period and the gate pin restarts charging up the gate of the mosfet. in the event of a severe short-circuit fault on the 12v output, the output current can surge to tens of amperes. the device responds within 1 f s to bring the current under control by pulling the gate to out voltage down with a 200ma current. almost immediately, the gate of the hot- swap mosfet recovers rapidly due to the r gate and c gate network, and load current is actively limited until the electronic circuit breaker times out. due to parasitic supply lead inductance, an input supply without any bypass capacitor may collapse during the high current surge and then spike upwards when the current is interrupted. circuit-breaker comparator and current limit the device features a programmable circuit-breaker threshold. the current limit can be selected by the connection of the cb pin. during startup, a foldback cur - rent limit is active to protect the internal mosfet to oper - ate within the soa (figure 1). programmable circuit-breaker current threshold the device features a programmable current limit with circuit-breaker function that protects the external mosfets against short circuits or excessive load current. the voltage across the external sense resistor, (r sense ) is monitored by an electronic circuit breaker (ecb) and active current limit (acl) amplifier. connect the cb pin to gnd, v s , or leave unconnected to select the electronics circuit-breaker threshold (table 1). the electronic circuit breaker turns off the hot-swap mosfet with a 500a current from gate to gnd if the voltage across the sense resistor exceeds v cb_th (cb) (50mv) for longer than the fault filter delay configured at the cdly pin. timer (cdly) an external capacitor connected from the cdly pin to gnd serves as fault filtering when the supply output is in active current limit. when the voltage across the sense resistor exceeds the circuit-breaker trip threshold (50mv), cdly pulls up with 100a. otherwise, it pulls down with 2a. the fault filter times out when the 1.2v cdly threshold is exceeded, causing the corresponding fault pin to pull low. the fault filter delay or circuit-breaker time delay is: t cb = c cdly x 12[ms/f] after the circuit-breaker timeout, the cdly pin capacitor pulls down with 2a from the 1.2v cdly threshold until it reaches 0.2v. then it completes 14 cooling cycles con - sisting of the cdly pin capacitor charging to 1.2v with a 100a current and discharging to 0.2v with a 2a current. at that point, the gate pin voltage is allowed to start up if the fault has been cleared as described in the resetting faults section. when the latched fault is cleared during the cool-off period, the corresponding fault pin pulls high. the total cool-off time for the mosfet after an overcurrent fault is: t cool = c cdly x 11[s/f] oring/hot-swap response in overload condition in the case where an overcurrent fault occurs on the out - put, the current is limited to a programmed current limit set through the cb pin. after a fault filter delay set by 100a current source in to the cdly pin capacitor, the circuit breaker trips, pulls the gate pin low, and turns off the hot- swap mosfet. the fault output is latched low. during the fault condition, the oring mosfet remains on. control inputs on input the device drives the og_ as soon as the v in1 - v f1 (v f1 is the forward voltage drop of oring mosfet connected to in1) or v in2 - v f2 (v f2 is the forward volt - age drop of the oring mosfet connected to in2) supply voltage generates a v on above the threshold voltage. an external resistive divider from csp to on and ground is used to set the turn-on voltage to any desired voltage from 2.9v to 5.5v. the ic turns on the corresponding oring mosfet and then turns on the hot-swap mosfet when v on > 1.22v. maxim integrated 13 MAX15068 dual oring, single hot-swap controller with accurate current monitoring www.maximintegrated.com
the device turns off the output when v on falls below v uv_ref (1.22v - v on_hys ). an external resistive divider from csp to on and ground is used to set the undervoltage-lockout threshold to any desired level between v uvlo and 18v. pulling the on pin voltage below 0.6v resets the electronic circuit breaker. monitoring analog current monitor output ipmon monitors the current delivered to the system. ip - mon has a 0 to 1.8v output voltage range. ipmon moni - tors the system input current. the device does not have a power monitor. the voltage at ipmon in this case is proportional to the input current by the following equation: v ipmon = g i x r ipmon x (v csp - v csn ) where g i = 0.3ms/v and r ipmon is the resistor to set the voltage overall voltage gain for ipmon. when connected as shown in the typical application circuit , ipmon monitors the input system current. leave ipmon unconnected if the function is not used. the maximum output of v ipmon should be limited to 1.8v to get best accuracy using proper r ipmon resistor value. output signals fault status output ( fault ) fault is an open-drain output that is internally pulled high by a 10a current source to a diode below v s , and can be pulled above v s using an external pullup. fault asserts low when the circuit breaker is tripped after an overcurrent fault timeout. leave fault unconnected if unused. power-good output ( pg ) internal circuitry monitors the hot-swap mosfet gate overdrive between the gate and out pins and the volt - age at the out pin. the power-good status for the supply is reported by the pg open-drain output. it is normally pulled high by an external pullup resistor or the internal 10a pullup. the power-good output asserts low when the gate overdrive exceeds 4.2v during the gate startup and the voltage at the out pin exceeds (0.9 x v csp ). the pg signal is delayed by 16ms once conditions for power- good are met. fault management autoretry when an overcurrent fault is latched after tripping the circuit breaker, the fault pin is asserted low. only the hot-swap mosfet is turned off, and the ideal diode mosfets are not affected. the latched fault is reset automatically after a cool-off timing cycle as described in the startup timer (cdly) section. at the end of the cool- off period, the fault latch is cleared and fault pulls high. the gate pin voltage is allowed to start up and turn on the hot-swap mosfet. if the output short persists, the supply powers up into a short with active current limiting until the circuit breaker times out and fault again pulls low. a new cool-off cycle begins with cdly ramping down with a 2a current. the whole process repeats itself until the output short is removed. since t cb and t cool are a function of cdly capacitance, c cdly , the autoretry duty cycle is equal to 0.1%, irrespective of c cdly . applications information prioritizing supplies with pc figure 2 shows an oring application where a resistive divider connected from in1 at the pc pin controls the turn- on of the oring mosfet, md2, in the in2 supply path. when the in1 supply voltage falls below 4.5v, it turns on the oring mosfet, md2, causing the oring output to be switched from the main 5.0v supply at in1 to the aux - iliary 5.0v supply at in2. this configuration permits the load to be supplied from a lower in1 supply as compared to in2 until in1 falls below the md2 turn-on threshold. the threshold value used should not allow the in1 supply to be operated at more than one diode voltage below in2. otherwise, md2 conducts through the mosfets body diode. the resistive divider connected from csp at the on pin provides the undervoltage threshold of 2.6v for the oring output supply. table 1. electronics circuit-breaker threshold programming cb pin connection electronic circuit-breaker threshold (v csp - v csn ) [mv] cb = gnd 35 cb = hi-z (unconnected) 50 cb = v s 65 maxim integrated 14 MAX15068 dual oring, single hot-swap controller with accurate current monitoring www.maximintegrated.com
figure 2. plug-in card in1 supply controls the in2 supply turn-on by the pc pin figure 2 cp 1 on en pc v s gnd cdly cb r sense 0 . 003 max 15068 69 . 8 k v main 5 . 0 v v aux 5 . 0 v 20 k 53 . 6 k 20 k in 1 og 1 md 1 cp 2 md 2 in 2 og 2 csp csn gate out 5 . 0 v fault pg ipmon 20 k maxim integrated 15 MAX15068 dual oring, single hot-swap controller with accurate current monitoring www.maximintegrated.com
+ denotes a lead(pb)-free/rohs-compliant package. * ep = exposed pad. part operating range function temp range pin-package MAX15068atp+ 3.7v to 18v autoretry, current monitor -40c to +125c 20 tqfn-ep* package type package code outline no. land pattern no. 20 tqfn t2045+1c 21-0726 cp1 on en v s pc cdly cb r sense 0.003 MAX15068 12v 137k 20k in1 og1 cp2 in2 og2 csp csn gate out 12v fault pg ipmon 20k 12v gnd maxim integrated 16 typical application circuit chip information process: bicmos ordering information package information for the latest package outline information and land patterns (footprints), go to www.maximintegrated.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. MAX15068 dual oring, single hot-swap controller with accurate current monitoring www.maximintegrated.com
revision number revision date description pages changed 0 12/13 initial release ? 2013 maxim integrated products, inc. 17 revision history maxim integrated cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a maxim integrated product. no circuit patent licenses are implied. maxim integrated reserves the right to change the circuitry and specifcations without notice at any time. the parametric values (min and max limits) shown in the electrical characteristics table are guaranteed. other parametric values quoted in this data sheet are provided for guidance. maxim integrated and the maxim integrated logo are trademarks of maxim integrated products, inc. MAX15068 dual oring, single hot-swap controller with accurate current monitoring for pricing, delivery, and ordering information, please contact maxim direct at 1-888-629-4642, or visit maxim integrateds website at www.maximintegrated.com.

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