_______________________________________________________________ maxim integrated products 1 for pricing, delivery, and ordering information, please contact maxim direct at 1-888-629-4642, or visit maxims website at www.maxim-ic.com. max5976a/max5976b 2.7v to 18v, 7a, hot-swap solution general description the max5976a/max5976b are integrated solutions for hot-swap applications requiring the safe insertion and removal of circuit line cards from a live backplane. the devices integrate a hot-swap controller, 24m i power mosfet, and electronic circuit-breaker protection in a single package. the ics are designed for protection of 2.7v to 18v supply voltages. the devices provide inrush current control and short- circuit detection during startup. during normal operation, the devices provide circuit-breaker protection against overload and short-circuit conditions. the circuit-breaker function disconnects the power to the load if the load current exceeds the circuit-breaker limit. the devices are factory-calibrated to deliver accurate overcurrent protection with q 10% accuracy. during a fault condi - tion, the max5976a enters an autoretry mode while the max5976b latches off. both versions feature a resistor- adjustable variable speed circuit-breaker threshold and overtemperature protection. additional features include power-good and fault indicator outputs. the ics are available in a 16-pin, 5mm x 5mm, tqfn- ep package and fully specified over the -40 c to +85 c operating temperature range. applications raid systems storage bridge bay disk drive power server i/o cards industrial features s 2.7v to 18v operating voltage range s 24m i internal power mosfet s 7a load current capability s no sense resistor required s 10% circuit-breaker threshold accuracy s adjustable circuit-breaker current s variable speed circuit-breaker response s thermal protection s power-good and fault outputs s latch-off or automatic retry options s drive-present signal input s active-low and active-high enables 19-5542; rev 1; 4/11 note: all devices are specified over the -40 c to +85 c operating temperature range. + denotes a lead(pb)-free/rohs-compliant package. * ep = exposed pad. ordering information typical application circuit evaluation kit available r1 in out presdet load (7a) v presdet on1 cb reg r2 r cb c reg gnd 2.7v to 18v 2.7v to 6v c in t vs max5976a max5976b fault pg p on2 r on2 r fault r pg v in removable card part pin package fault management max5976a ete+ 16 tqfn-ep* autoretry max5976b ete+ 16 tqfn-ep* latched off
max5976a/max5976b 2.7v to 18v, 7a, hot-swap solution 2 stresses beyond those listed under absolute maximum ratings may cause permanent damage to the device. these are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. exposure to absolute maximum rating conditions for extended periods may affect device reliability. in to gnd .............................................................. -0.3v to +20v cb to gnd .............................................. -0.3v to (v reg + 0.3v) on1, reg to gnd .................................................. -0.3v to +6v out, on2 , presdet to gnd ............... -0.3v to the lower of (v in + 0.3v) and +20v pg, fault to gnd ............................................... -0.3v to +26v continuous power dissipation (t a = +70 n c) tqfn (derate 33.3mw/ n c above +70 n c) (note 1) ..2666.7mw operating ambient temperature range ........... -40 n c to +85 n c maximum junction temperature ..................................... +150 n c storage temperature range ............................ -60 n c to +150 n c lead temperature (soldering, 10s) ................................ +300 n c soldering temperature (reflow) ...................................... +260 n c electrical characteristics (v in = 12v, v on1 = 2v, v on2 = v presdet = 0v, r cb = 40k i , t a = t j = -40 n c to +85 n c, unless otherwise noted. typical values are at t a = +25 n c.) (note 3) absolute maximum ratings note 2: package thermal resistances were obtained using the method described in jedec specification jesd51-7, using a four- layer board. for detailed information on package thermal considerations , refer to www.maxim-ic.com/thermal-tutorial . tqfn junction-to-case thermal resistance ( b jc ) ................... 30 n c/w junction-to-ambient thermal resistance ( b ja ) ............... ...2 n c/w package thermal characteristics (note 2) note 1: as per jedec51 standard (multilayer board). parameter symbol conditions min typ max units input supply voltage range v in 2.7 18 v input supply current i in v on1 = 3v, no load, 7a current-limit threshold 5 7.5 ma default undervoltage lockout v uvlo v in rising, v on1 = v in 2.35 2.5 2.65 v default undervoltage lockout hysteresis v uvlo_hys 0.1 v on1 turn-on threshold v on1_th v on1 rising 1.17 1.21 1.25 v on1 turn-on threshold hysteresis v on1_hys v on1 falling 0.1 v on1 input bias current i on1 v on1 = 0 to 5v -1 +1 f a current limit circuit-breaker accuracy (at startup) i cb,th r cb = 40k i 6.3 7 7.7 a r cb = 28.57k i 4.5 5 5.5 r cb = 20k i 3.15 3.5 3.85 r cb = 10k i 1.575 1.75 1.925 slow-comparator response time (note 4) t scd 0.6% overcurrent 2.7 ms 30% overcurrent 200 f s mosfet total on-resistance r on 15 24 41 m i logic inputs ( on2 , presdet ) low voltage input v il 2.7v < v in < 18v 0.4 v high voltage input v ih 2.7v < v in < 18v 1.4 v input current i in v on2 , v presdet = 0 to 6v -1 +1 f a
max5976a/max5976b 2.7v to 18v, 7a, hot-swap solution 3 electrical characteristics (continued) (v in = 12v, v on1 = 2v, v on2 = v presdet = 0v, r cb = 40k i , t a = t j = -40 n c to +85 n c, unless otherwise noted. typical values are at t a = +25 n c.) (note 3) note 3: all devices are 100% production tested at t a = +25 c . limits over temperature are guaranteed by design. note 4: the current-limit slow-comparator response time is weighed against the amount of overcurrent so that the higher the over - current condition, the faster the response time. typical operating characteristics (v in = 12v, v on1 = 2v, r cb = 40k, v on2 = v presdet = 0v, t a = +25 c, unless otherwise noted.) supply current vs. temperature max5976 toc01 temperature (c) supply current (ma) 60 35 10 -15 4.5 5.0 5.5 6.0 4.0 -40 85 v on1 = 2v v in = 12v v in = 3v v in = 5v circuit-breaker threshold vs. circuit-breaker resistance max5976 toc02 r cb (ki) circuit-breaker threshold (a) 35 30 25 20 15 2 4 6 8 10 0 10 40 v in = 12v circuit-breaker threshold vs. temperature max5976 toc03 temperature (c) circuit-breaker threshold (a) 60 35 10 -15 2 4 6 8 10 0 -40 85 v in = 12v r cb = 39.3ki r cb = 30.1ki r cb = 19.9ki r cb = 10ki parameter symbol conditions min typ max units open-drain outputs fault , pg output low voltage v ol low-impedance state, i fault = i pg = 5ma 0.4 v fault , pg output high leakage current i oh high-impedance state, v fault = v pg = 16v 1 f a out bias current i out v on1 = gnd 10 f a timing automatic restart delay after current-limit timeout t off 250 ms pg assertion delay t pg from v out > v pg 16 ms pg threshold v pg v out = 12v 0.9 x v in v thermal protection thermal-shutdown threshold 150 n c thermal-shutdown threshold hysteresis 20 n c
max5976a/max5976b 2.7v to 18v, 7a, hot-swap solution 4 typical operating characteristics (continued) (v in = 12v, v on1 = 2v, r cb = 40k, v on2 = v presdet = 0v, t a = +25 c, unless otherwise noted.) on-resistance vs. temperature max5976 toc04 temperature (c) on-resistance (mi) 60 35 10 -15 25 30 35 40 20 -40 85 v in = 12v i load = 100ma turn-on waveform max5976 toc05 v on1 2v/div v out 10v/div v pg 10v/div i load 5a/div 0a 0v 0v 0v 4ms/div i load = 5a normal turn-off waveform max5976 toc06 v on1 2v/div v out 10v/div v pg 10v/div i load 5a/div 0a 0v 0v 0v 4ms/div i load = 5a fault shutdown waveform?overload (slow trip) max5976 toc07 v out 10v/div v fault 10v/div v pg 10v/div i load 2a/div 0v 0v 0a 0v 2ms/div fault shutdown waveform?short circuit max5976 toc08 v out 10v/div v fault 10v/div v pg 10v/div i load 10a/div 0v 0v 0a 0v 4ms/div on1 rising / falling threshold voltage vs. temperature max5976 toc09 temperature (c) v on1 rising / falling threshold voltage 60 35 10 -15 1.12 1.14 1.16 1.18 1.20 1.22 1.24 1.10 -40 85 v on1 rising v on1 falling pg assertion delay max5976 toc10 v on1 1v/div v out 5v/div v pg 5v/div 0v 0v 0v 4ms/div autoretry functionality max5976 toc11 v out 500mv/div 0v 0v 0v 40ms/div i load 2a/div v fault 10v/div i load = 7a circuit-breaker threshold time vs. overcurrent max5976 toc12 overcurrent (%) circuit-breaker threshold time (ms) 2500 2000 1500 1000 500 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 2.2 2.4 2.6 2.8 3.0 0 0 3000 v in = 12v r cb = 19.9ki
max5976a/max5976b 2.7v to 18v, 7a, hot-swap solution 5 pin description pin configuration pin name function 1 gnd ground 2C5 in supply voltage input. in is connected to the drain of the internal 24m i mosfet. bypass in with 1 f f capacitor to ground. add a transient voltage suppressor diode from in to gnd for output short-circuit protection. 6 fault fault status output. fault is an open-drain, active-low output. fault asserts low when an over - current or overtemperature condition triggers a shutdown. 7 pg power-good output. pg is an open-drain, active-high output. pg pulls low until the internal power mosfet is fully enhanced. 8C11 out load connection point. source of the internal power mosfet. 12 presdet active-low present-detect logic input. pulling presdet to gnd enables the output if on2 is low and on1 is high. 13 on2 active-low enable logic input. pulling on2 to gnd enables the output if presdet is low and on1 is high. 14 cb current-limit threshold set. connect a resistor from cb to gnd to set the circuit-breaker threshold. 15 reg internal regulator output. bypass to ground with a 1 f f capacitor. do not power external circuitry using the reg output. 16 on1 active-high enable comparator input. pulling on1 high enables the output if presdet and on2 are held low. on1 also sets the undervoltage threshold. see the s etting the undervoltage threshold section. ep exposed pad. ep is internally grounded. connect externally to ground plane for effective heat dis - sipation. do not use as the only ground connection. 15 16 14 13 6 5 7 in in gnd ep* *connect ep to gnd. out out presdet 1 2 cb 4 12 11 9 reg on1 out pg fault in ma5976a ma5976b in out 3 10 on2 tqfn + top view 8
max5976a/max5976b 2.7v to 18v, 7a, hot-swap solution 6 functional diagram presdet temp sense 2500x fault pg out 2x 15 a 1ma cb_comp sns_ok 1v on2 reg cb gnd 1.21v uvlo v reg on1 in s set control logic clr r q q ldo o.9 x v in reference generator max5976a max5976b charge pump 6 a 10 a 1.25v
max5976a/max5976b 2.7v to 18v, 7a, hot-swap solution 7 detailed description enable logic and undervoltage lockout threshold the max5976a/max5976b enable the output as shown in table 1. the ics turn on the output only when v on1 is high (v on1 > 1.21v) while on2 and presdet are low. the devices turn off the output when v on1 falls below 1.21v - v hys or whenever on2 or presdet are above v ih . a resistive divider from in to on1 and ground provides the flexibility to set the undervoltage lockout threshold to any desired level between v uvlo and 18v. see figure 1 and setting the undervoltage threshold in the applications information section. startup once the max5976a/max5976b output is enabled, the device provides controlled application of power to a load. the voltage at out will begin to rise at approximately 18kv/s until the programmed circuit-breaker current level is reached, at which time the max5976a/max5976b will actively limit inrush current at the circuit-breaker setting. because of this, the inrush current can be easily pro - grammed by appropriate selection of r cb. this startup mode of operation will continue for up to 16ms; after the startup time elapses, the output will either have risen to the in potential, or if the device is still in current limit, it will shut down and assert the fault output low. the resulting dv out /dt during startup can be deter - mined according to the following equation: dv out /dt (i cb - i load )/c out in this equation, i load is any current drawn by a load device during the output ramp time that does not charge c out . make certain that r cb is chosen such that: v in x c out /(i cb - i load ) < 16ms this ensures that the output capacitance can be fully charged before the 16ms startup timer elapses. an open-drain power-good output goes high-impedance 16ms (typ) after the output has risen to more than 90% of the input voltage to indicate a successful startup. charge pump an integrated charge pump provides the gate-drive volt - age for the internal power mosfet. the charge pump generates +5v potential above v in to fully enhance the internal power mosfet. circuit-breaker comparator the current through the internal power mosfet is com - pared to a circuit-breaker threshold. an external resistor between cb and ground sets this threshold. the circuit-breaker comparator is designed so that the load current can exceed the threshold for some amount of time before tripping. the time delay varies inversely with the overdrive above the threshold. the greater the overcurrent condition, the faster the response time allow - ing the devices to tolerate load transients and noise near the circuit-breaker threshold. the ics also feature catastrophic short-circuit protec - tion. during normal operation, if out is shorted directly to ground, a fast protection circuit forces the gate of the internal mosfet to discharge quickly and disconnect the output from the input. autoretry/latch-off during a fault condition, the devices turn off the inter - nal mosfet disconnecting the output from the input. the max5976a enters an autoretry mode with a fixed 250ms lockout time before reconnect can occur. the max5676b latches off and remains off until the enable logic is cycled off and on. figure 1. undervoltage threshold setting table 1. output enable truth table x = dont care. v on1_th = 1.21v (typ). on2 on1 r1 r2 v in max5976a max5976b presdet active- high enable 1.21v precision analog input on1 logic inputs out on2 presdet v on1 > v on1_th 0 0 on v on1 < (v on1_th - v on_hys ) x x off x 1 x off x x 1 off
max5976a/max5976b 2.7v to 18v, 7a, hot-swap solution 8 power-good delay the devices feature an open-drain, power-good output that asserts after 16ms (typ), indicating that out has reached (0.9 x v in ) voltage. reg the devices include a linear regulator that outputs 2.6v at reg. reg provides power to the internal circuit blocks of the ics and must not be loaded externally. reg requires a 1 f f capacitor to ground for proper operation. fault status output ( fault ) fault is an open-drain output that pulls low when a cur - rent limit or an overtemperature fault shutdown occurs. fault remains low until the next startup cycle. fault is capable of sinking up to 5ma when asserted. thermal protection the devices enter a thermal shutdown mode in the event of overheating caused by excessive power dissipation or high ambient temperature. when the junction tem - perature exceeds t j = +150 n c (typ), the internal thermal protection circuitry turns off the internal power mosfet. the devices recover from thermal shutdown mode once the junction temperature drops by 20 n c (typ). applications information setting the undervoltage threshold the devices feature an independent on/off control (on1) for the internal mosfet. the devices operate with a 2.7v to 18v input voltage range and has a default 2.5v (typ) undervoltage lockout threshold. the internal mosfet remains off as long as v in < 2.5v and/or v on1 < v on1_th . the undervoltage lockout threshold is pro - grammabl e using a resistive divider between on1 and gnd (figure 1). when v in is greater than 2.7v and v on1 exceeds the 1.21v (typ) threshold, the gate of the inter - nal mosfet enhances to 5v, with respect to v in and the devices' internal switch goes into normal operation. use the following equation to calculate the resistors values for the desired undervoltage threshold: in on1_th v r1 - 1 r2 v ? ? = ? ? ? ? ? ? where v in is the desired turn-on voltage for the output and v on1 is 1.21v. r1 and r2 create a resistive divider from v in to on1. during normal operating conditions, v on1 must remain above its 1.21v (typ) threshold. if v on1 falls 100mv (v on1_hys ) below the threshold, the internal mosfet turns off, disconnecting the load from the input. setting the current limit an external resistor from cb to ground sets the current limit for the devices. use the following formula to set the current limit: limit cb 0.175a i (a) r ( ) 1000 ? ? = ? ? ? ? ? ? package information for the latest package outline information and land patterns, go to www.maxim-ic.com/packages . note that a +, #, or - in the package code indicates rohs status only. package drawings may show a different suffix character, but the drawing pertains to the package regardless of rohs status. chip information process: bicmos package type package code outline no. land pattern no. 16 tqfn-ep t1655+3 21-0140 90-0073
maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a maxim product. no circuit patent licenses are implied. maxim reserves the right to change the circuitry and specifications without notice at any time. maxim integrated products, 120 san gabriel drive, sunnyvale, ca 94086 408-737-7600 9 ? 2011 maxim integrated products maxim is a registered trademark of maxim integrated products, inc. max5976a/max5976b 2.7v to 18v, 7a, hot-swap solution revision history revision number revision date description pages changed 0 9/10 initial release 1 4/11 added the package thermal characteristics and startup sections. 2, 7
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