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general description the MAX5946 dual hot-plug controller is designed for pci express applications. the device provides hot- plug control for 12v, 3.3v, and 3.3v auxiliary supplies of two pci express slots. the MAX5946? logic inputs/out- puts allow interfacing directly with the system hot-plug management controller or through an smbus with an external i/o expander. an integrated debounced atten- tion switch and present-detect signals are included to simplify system design. the MAX5946 drives four external n-channel mosfets to control the 12v and 3.3v main outputs. the 3.3v aux- iliary outputs are controlled through internal 0.3 ? n-channel mosfets. internal charge pumps provide gate drive for the 12v outputs while the gate drive of the 3.3v output is driven by the 12v input supply. the 3.3v auxiliary outputs are completely independent from the main outputs with their own charge pumps. at power-up, the MAX5946 keeps all of the external mosfets off until the supplies rise above their respec- tive undervoltage lockout (uvlo) thresholds. the device keeps the internal mosfets off only until the auxiliary input supply rises above its uvlo threshold. upon a turn-on command, the MAX5946 enhances the external and internal mosfets slowly with a constant gate current to limit the power-supply inrush current. the MAX5946 actively limits the current of all outputs at all times and shuts down if an overcurrent condition persists for longer than a programmable overcurrent timeout. thermal-protection circuitry also shuts down all outputs if the die temperature exceeds +150 c. after an overcurrent or overtemperature fault condition, the MAX5946l latches off while the MAX5946a automatical- ly restarts after a restart time delay. the device is avail- able in a 36-pin (6mm 6mm) thin qfn package and operates over the -40 c to +85 c temperature range. applications servers desktop mobile server platforms workstations embedded devices features ? pci express compliant ? hot swaps 12v, 3.3v, and 3.3v auxiliary for 2 pci-e slots ? integrated power mosfet for auxiliary supply rails ? controls di/dt and dv/dt ? active current limiting protects against overcurrent/short-circuit conditions ? programmable current-limit timeout ? pwrgd signal outputs with programmable power-on reset (por) (160ms default) ? latched fault signal output after overcurrent or overtemperature fault ? attention switch inputs/outputs with 4ms debounce ? present-detect inputs ? forced-on inputs facilitates testing ? thermal shutdown ? allows control through smbus with an i/o expander MAX5946 dual pci express, hot-plug controller ________________________________________________________________ maxim integrated products 1 19-3483; rev 0; 11/04 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. evaluation kit available onb auxonb 12sb+ 12gb 3.3sb+ 3.3sb- pres-detb 1 2 3 4 5 6 7 8 9 27 26 25 24 23 22 21 20 19 3.3vauxin 3.3vauxob pwrgdb 3.3gb 3.3vauxoa pwrgda faulta 3.3ga pgnd gnd 12vin input1 output1 output2 input2 tim poradj thin qfn MAX5946 top view 12sb- faultb fonb ona auxona 12sa+ 12ga 3.3sa+ 3.3sa- pres-deta 12sa- fona 36 35 34 33 32 31 30 29 28 10 11 12 13 14 15 16 17 18 pin configuration ordering information part temp range pin-package MAX5946aetx -40? to +85? 36 thin qfn MAX5946letx -40? to +85? 36 thin qfn typical application circuit appears at end of data sheet. smbus is a trademark of intel corp. pci express is a trademark of pci-sig corp.
MAX5946 dual pci express, hot-plug controller 2 _______________________________________________________________________________________ absolute maximum ratings 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. (all voltages referenced to gnd, unless otherwise noted.) 12vin......................................................................-0.3v to +14v 12ga, 12gb ..............................................-0.3v to (v 12vin + 6v) 12sa+, 12sa-, 12sb+, 12sb-, 3.3ga, 3.3gb .....................................-0.3v to (v 12vin + 0.3v) 3.3vauxin, ona, onb, faulta , faultb ............-0.3v to +6v pwrgda , pwrgdb ................................................-0.3v to +6v pgnd ....................................................................-0.3v to +0.3v all other pins to gnd......................-0.3v to (v 3.3vauxin + 0.3v) continuous power dissipation (t a = +70?) 36-pin thin qfn (derate 26.3mw/? above +70?).....2.105w operating temperature range ...........................-40? to +85? junction temperature ......................................................+150? storage temperature range .............................-65? to +150? lead temperature (soldering, 10s) .................................+300? electrical characteristics (v 12vin = v 12s_- = v 12s_+ = 12v, v 3.3s_+ = v 3.3s_- = v 3.3vauxin = v on_ = v auxon_ = v fon_ _ = 3.3v, pwrgd_ = fault_ = poradj = tim = output_ = 12g_ = 3.3g_ = open, input_ = pres_det_ = pgnd = gnd, t a = -40? to +85?, unless otherwise noted. typical values are at t a = +25?.) (note 1) parameter symbol conditions min typ max units 12v supply 12v supply voltage range v 12vin 10.8 12 13.2 v v 12vin rising 9.5 10 10.5 12vin undervoltage lockout v 12uvlo hysteresis 0.1 v 12vin supply current i 12vin v 12vin = 13.2v 0.5 1ma 12vin control 12vin current-limit threshold (v 12s_+ - v 12s_- ) v 12ilim 49 54 59 mv 12g_ gate charge current i 12g_chg v 12g_ = gnd 4 5 6 ? normal turn-off, on_ = gnd, v 12g _ = 2v 50 150 250 ? 12g_ gate discharge current i 12g_dis o utp ut shor t- ci r cui t cond i ti on, str ong g ate p ul l d ow n to r eg ul ati on, v 1 2v in - v 1 2s _ 1v , v 1 2g_ = 5v 50 120 180 ma 12g_ gate high voltage (v 12g_ - v 12vin ) v 12g_h i 12g_ = 1? 4.8 5.3 5.8 v 12g_ threshold voltage for pwrgd_ assertion (note 2) v pgth12 referred to v 12vin , i 12g_ = 1? -3.0 -4 -4.8 v 12s_- input bias current 1a 12s_+ input bias current 20 60 ? 3.3v supply 3.3v supply voltage range v 3.3sa+ , v 3.3sb+ 3.0 3.3 3.6 v 3.3sa+ rising 2.52 2.65 2.78 v undervoltage lockout (note 3) hysteresis 30 mv
MAX5946 dual pci express, hot-plug controller _______________________________________________________________________________________ 3 electrical characteristics (continued) (v 12vin = v 12s_- = v 12s_+ = 12v, v 3.3s_+ = v 3.3s_- = v 3.3vauxin = v on_ = v auxon_ = v fon_ _ = 3.3v, pwrgd_ = fault_ = poradj = tim = output_ = 12g_ = 3.3g_ = open, input_ = pres_det_ = pgnd = gnd, t a = -40? to +85?, unless otherwise noted. typical values are at t a = +25?.) (note 1) parameter symbol conditions min typ max units 3.3v control 3.3v current-limit threshold (v 3.3s_+ - v 3.3s_- ) v 3.3ilim 17 20 23 mv 3.3g_ gate charge current i 3.3g_chg v 3.3g_ = gnd 4 5 6 ? on_ = gnd, v 3.3g_ = 2v 50 150 250 ? 3.3g_ gate discharge current i 3.3g_dis o utp ut shor t- ci r cui t cond i ti on, str ong g ate p ul l d ow n to r eg ul ati on, v 3 .3 s _ + - v 3 .3 s _ 1v , v 3 .3 g_ = 5v 100 150 220 ma 3.3g_ gate high voltage (v 3.3g_ - v 3.3s_+ ) v 3.3g_h sourcing 1? 4.5 5.5 6.8 v 3.3g_ threshold voltage for pwrgd_ assertion (note 2) v pgth3.3 referred to v 3.3vauxin , i 3.3g_ = 1? -3.0 -4 -4.5 v 3.3s_- input bias current 1a 3.3s_+ input bias current 20 60 ? 3.3v auxiliary supply 3.3vauxin supply voltage range v 3.3vauxin 3.0 3.3 3.6 v 3.3vauxin rising 2.52 2.65 2.78 v 3.3vauxin undervoltage lockout v 3 .3 v a u x u v l o hysteresis 30 mv 3.3vauxin supply current v 3.3vauxin = 3.6v 1.5 3ma 3.3vauxin to 3.3vauxo_ maximum dropout i 3.3vauxo_ = 375ma 225 mv 3.3vauxo_ current-limit threshold 3.3vauxo_ shorted to gnd 376 470 564 ma 3.3vauxo_ threshold for pwrgd_ assertion (v 3.3vauxin - v 3.3vauxo_ ) (note 3) v pgth3.3aux 400 mv logic signals rising edge 1.0 2.0 v input-logic threshold (on_, fon_ , auxon_, pres-det_ , input_) hysteresis 25 mv input bias current (on_, auxon_, input_) 1a fon_ , pres-det_ internal pullup 25 50 75 k ? on_, auxon_ high-to-low deglitch time 4s
MAX5946 dual pci express, hot-plug controller 4 _______________________________________________________________________________________ electrical characteristics (continued) (v 12vin = v 12s_- = v 12s_+ = 12v, v 3.3s_+ = v 3.3s_- = v 3.3vauxin = v on_ = v auxon_ = v fon_ _ = 3.3v, pwrgd_ = fault_ = poradj = tim = output_ = 12g_ = 3.3g_ = open, input_ = pres_det_ = pgnd = gnd, t a = -40? to +85?, unless otherwise noted. typical values are at t a = +25?.) (note 1) parameter symbol conditions min typ max units pres-det_ high-to-low deglitch time t deg 357ms poradj = open 90 160 250 r poradj = 20k ? ? pwrgd_ power-on reset time (note 2) t por_hl r poradj = 200k ? pwrgd_ low-to-high deglitch time t por_lh 4s sinking 2ma 0.1 pwrgd_ , fault_ output low voltage sinking 30ma 0.7 v pwrgd_ , fault_ output- high leakage current v pwrgd_ = v fault_ = 5.5v 1 a tim = open 5.5 11 17.0 r tim = 15k ? ? fault_ timeout t fault r tim = 300k ? fault_ timeout during startup t su 2 x t fault ms autorestart delay time t restart 64 x t fault ms fault reset minimum pulse width (note 4) t reset 100 ? thermal-shutdown threshold t sd t j rising +150 ? thermal-shutdown threshold hysteresis 20 ? output_ debounce time t dbc 2.6 4.4 6.2 ms output_ high voltage sourcing 2ma v 3.3vauxin - 0.3 v 3.3 v au x in v output_ low voltage sinking 2ma 0.4 v note 1: 100% production tested at t a = +25?. parameters over temperature are guaranteed by design. note 2: pwrgd_ asserts a time t por_hl after v pgth12 , v pgth3.3 , and v pgth3.3aux conditions are met. note 3: the uvlo for the 3.3v supply is sensed at 3.3sa+. note 4: this is the time that on_ or auxon_ must stay low when resetting a fault condition.
MAX5946 dual pci express, hot-plug controller _______________________________________________________________________________________ 5 12vin input supply current vs. temperature MAX5946 toc01 temperature ( c) supply current (ma) 60 35 10 -15 0.491 0.492 0.493 0.494 0.495 0.496 0.497 0.498 0.499 0.500 0.501 0.502 0.503 0.504 0.505 0.490 -40 85 3.3vauxin supply current vs. temperature MAX5946 toc02 temperature ( c) supply current (ma) 60 35 10 -15 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 0 -40 85 on and auxon low-to-high threshold voltage vs. temperature MAX5946 toc03 temperature ( c) threshold voltage (v) 60 35 10 -15 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 1.9 2.0 1.0 -40 85 on_ or auxon_ 3.3vauxo_ output voltage vs. current MAX5946 toc04 output current (a) output voltage (v) 0.5 0.4 0.3 0.2 0.1 0.5 1.0 1.5 2.0 2.5 3.0 3.5 0 00.6 12g_ and 3.3g_ gate charge current vs. temperature MAX5946 toc05 temperature ( c) gate charge current ( a) 60 35 10 -15 4.90 4.95 5.00 5.05 5.10 5.15 5.20 5.25 5.30 5.35 4.85 -40 85 12g_ 3.3g_ 12g_ and 3.3g_ gate discharge current vs. temperature MAX5946 toc06 temperature ( c) gate discharge current ( a) 60 35 10 -15 150 155 160 165 170 145 -40 85 3.3g_ 12g_ 3.3vaux internal switch maximum dropout vs. temperature MAX5946 toc07 temperature ( c) dropout voltage (v) 60 35 10 -15 0.02 0.04 0.06 0.08 0.10 0.12 0.14 0.16 0.18 0.20 0 -40 85 auxiliary output current = 375ma 12v and 3.3v current-limit threshold voltage vs. temperature MAX5946 toc08 temperature ( c) current-limit threshold voltage (mv) 60 35 10 -15 10 20 30 40 50 60 0 -40 85 12v current-sense threshold 3.3v current-sense threshold auxiliary current limit vs. temperature MAX5946 toc09 temperature ( c) auxiliary current limit (a) 60 35 10 -15 0.455 0.460 0.465 0.470 0.475 0.480 0.485 0.490 0.495 0.500 0.450 -40 85 t ypical operating characteristics (v 12vin = v 12sa+ = 12v, v 3.3vauxin = v 3.3s_+ = v on_ = v auxon_ = v input_ = 3.3v, pres-det_ = gnd, fon_ = poradj = tim = float, fault_ = 10k ? to 3.3vauxin, pwrgda = 10k ? to 3.3vauxo_, t a = +25?, unless otherwise noted, see the typical application circuit .)
MAX5946 dual pci express, hot-plug controller 6 _______________________________________________________________________________________ t ypical operating characteristics (continued) (v 12vin = v 12sa+ = 12v, v 3.3vauxin = v 3.3s_+ = v on_ = v auxon_ = v input_ = 3.3v, pres-det_ = gnd, fon_ = poradj = tim = float, fault_ = 10k ? to 3.3vauxin, pwrgda = 10k ? to 3.3vauxo_, t a = +25?, unless otherwise noted, see the typical application circuit .) 12vin undervoltage lockout threshold vs. temperature MAX5946 toc10 temperature ( c) uvlo threshold (v) 60 35 -15 10 9.85 9.90 9.95 10.00 10.05 10.10 10.15 10.20 9.80 -40 85 3.3vauxin undervoltage lockout threshold vs. temperature MAX5946 toc11 temperature ( c) uvlo threshold (v) 60 35 10 -15 2.62 2.64 2.66 2.68 2.70 2.60 -40 85 12v turn-on/off time MAX5946 toc12 12g_ 20v/div pwrgd_ 5v/div on_ 5v/div 12v output 10v/div 40ms/div 3.3v turn-on/off time MAX5946 toc13 3.3g_ 10v/div pwrgd_ 5v/div on_ 5v/div 3.3v output 5v/div 40ms/div 3.3v auxiliary turn-on/off time MAX5946 toc14 40ms/div 3.3auxo_ output voltage 2v/div auxon_ 2v/div pwrgd 2v/div 12v power-up MAX5946 toc15 12v output 10v/div pwrgd_ 5v/div 12vin, 12v input 10v/div 12g_ 20v/div 40ms/div
MAX5946 dual pci express, hot-plug controller _______________________________________________________________________________________ 7 t ypical operating characteristics (continued) (v 12vin = v 12sa+ = 12v, v 3.3vauxin = v 3.3s_+ = v on_ = v auxon_ = v input_ = 3.3v, pres-det_ = gnd, fon_ = poradj = tim = float, fault_ = 10k ? to 3.3vauxin, pwrgda = 10k ? to 3.3vauxo_, t a = +25?, unless otherwise noted, see the typical application circuit .) 3.3v input/3.3v auxiliary input power-up MAX5946 toc16 3.3v output 5v/div pwrgd_ 5v/div 3.3vauxo_ 5v/div 3.3g_ 10v/div 100ms/div 3.3s_+ 5v/div turn-on delay 3.3v output and 3.3v auxiliary output MAX5946 toc17 4ms/div 5v/div 5v/div 5v/div 5v/div 10v/div 3.3vauxo_ output voltage 3.3 output voltage 3.3 input, 3.3vauxin 3.3g_ pwrgd fault condition on 12v output (autorestart option MAX5946a) MAX5946 toc18 12g_ 20v/div fault_ 5v/div 12v output current 5a/div 100ms/div 12v output voltage 10v/div t restart r load step to 1.5 ? fault condition on 3.3v output (autorestart option MAX5946a) MAX5946 toc19 3.3g_ 10v/div fault_ 5v/div 3.3v main output current 2a/div 100ms/div 3.3v output voltage 5v/div t restart r load step to 0.5 ? fault condition on auxiliary output (autorestart option MAX5946a) MAX5946 toc20 fault_ 2v/div 3.3vauxo_ output current 500ma/div 100ms/div 3.3vauxo_ output voltage 2v/div t restart r load step to 4 ? fault condition on 12v output (latch option MAX5946l) MAX5946 toc21 12g_ 20v/div fault_ 5v/div 12v output current 5a/div 100ms/div 12v output voltage 10v/div r load step to 1.5 ?
MAX5946 dual pci express, hot-plug controller 8 _______________________________________________________________________________________ t ypical operating characteristics (continued) (v 12vin = v 12sa+ = 12v, v 3.3vauxin = v 3.3s_+ = v on_ = v auxon_ = v input_ = 3.3v, pres-det_ = gnd, fon_ = poradj = tim = float, fault_ = 10k ? to 3.3vauxin, pwrgda = 10k ? to 3.3vauxo_, t a = +25?, unless otherwise noted, see the typical application circuit .) fault condition on 12v output MAX5946 toc22 12g_ 20v/div fault_ 5v/div 12v output current 5a/div 4ms/div 12v output voltage 10v/div r load step to 1.5 ? t fault fault condition on 3.3v output (latch option MAX5946l) MAX5946 toc23 3.3g_ 10v/div fault_ 5v/div 3.3v output current 2a/div 100ms/div 3.3v output voltage 5v/div r load step to 0.5 ? fault condition on 3.3v main output MAX5946 toc24 3.3g_ 10v/div fault_ 5v/div 3.3v output current 2a/div 4ms/div 3.3v output voltage 5v/div r load step to 0.5 ? t fault fault condition on auxiliary output (latch option MAX5946l) MAX5946 toc25 fault_ 2v/div 3.3vauxo_ output current 500ma/div 100ms/div 3.3vauxo_ output voltage 2v/div r load step to 4 ? fault condition on auxiliary output MAX5946 toc26 fault_ 2v/div 3.3vauxo_ output current 500ma/div 4ms/div 3.3vauxo_ output voltage 2v/div r load step to 4 ? t fault short circuit on 12v output MAX5946 toc27 12g_ 20v/div fault_ 5v/div 12v output current 5a/div 2ms/div 12v output voltage 10v/div
MAX5946 dual pci express, hot-plug controller _______________________________________________________________________________________ 9 t ypical operating characteristics (continued) (v 12vin = v 12sa+ = 12v, v 3.3vauxin = v 3.3s_+ = v on_ = v auxon_ = v input_ = 3.3v, pres-det_ = gnd, fon_ = poradj = tim = float, fault_ = 10k ? to 3.3vauxin, pwrgda = 10k ? to 3.3vauxo_, t a = +25?, unless otherwise noted, see the typical application circuit .) short circuit on 12v output MAX5946 toc28 12g_ 20v/div fault_ 5v/div 12v output current 25a/div 4 s/div 12v output voltage 10v/div 0v 0v 0v short circuit on 3.3v output MAX5946 toc29 3.3g_ 5v/div fault_ 5v/div 3.3v output current 2a/div 2ms/div 3.3v output voltage 5v/div short circuit on 3.3v output MAX5946 toc30 3.3g_ 5v/div fault_ 5v/div 3.3v output current 10a/div 2 s/div 3.3v output voltage 5v/div 0v short circuit on 3.3auxo_ MAX5946 toc31 fault_ 5v/div 3.3vauxo_ output current 500ma/div 2ms/div 3.3vauxo_ output voltage 2v/div short circuit on 3.3vauxo_ MAX5946 toc32 fault_ 5v/div 3.3vauxo_ output current 5a/div 2 s/div 3.3vauxo_ output voltage 2v/div power-up into fault (auxiliary supply) MAX5946 toc33 3.3vauxo_ output voltage 2v/div fault_ 5v/div 3.3vauxo_ output current 500ma/div 4ms/div auxon_ 5v/div t su r load = 4 ?
MAX5946 dual pci express, hot-plug controller 10 ______________________________________________________________________________________ t ypical operating characteristics (continued) (v 12vin = v 12sa+ = 12v, v 3.3vauxin = v 3.3s_+ = v on_ = v auxon_ = v input_ = 3.3v, pres-det_ = gnd, fon_ = poradj = tim = float, fault_ = 10k ? to 3.3vauxin, pwrgda = 10k ? to 3.3vauxo_, t a = +25?, unless otherwise noted, see the typical application circuit .) power-up into fault (3.3v main) MAX5946 toc34 3.3v output voltage 2v/div fault_ 5v/div 3.3v output current 4a/div 4ms/div on_, auxon_ 5v/div t su r load = 0.5 ? 3.3g_ 5v/div power-up into fault (12v output) MAX5946 toc35 12v output voltage 10v/div fault_ 5v/div 12v output current 5a/div 4ms/div on_, auxon_ 5v/div t su 12g_ 10v/div present-detect (on/off) operation MAX5946 toc36 40ms/div 5v/div 5v/div 5v/div 10v/div 12v output voltage 3.3vauxo_ output voltage pwrgd pres-det_ present-detect (on/off) operation MAX5946 toc37 4ms/div 5v/div 5v/div 5v/div 10v/div 12v output voltage 3.3vauxo_ output voltage pwrgd pres-det_ forced-on (on/off) operation MAX5946 toc38 40ms/div 5v/div 5v/div 5v/div 10v/div 12v output voltage 3.3vauxo_ output voltage pwrgd fon_ forced-on (on/off) operation MAX5946 toc39 4ms/div 5v/div 5v/div 5v/div 10v/div 12v output voltage 3.3vauxo_ output voltage pwrgd fon_
MAX5946 dual pci express, hot-plug controller ______________________________________________________________________________________ 11 t ypical operating characteristics (continued) (v 12vin = v 12sa+ = 12v, v 3.3vauxin = v 3.3s_+ = v on_ = v auxon_ = v input_ = 3.3v, pres-det_ = gnd, fon_ = poradj = tim = float, fault_ = 10k ? to 3.3vauxin, pwrgda = 10k ? to 3.3vauxo_, t a = +25?, unless otherwise noted, see the typical application circuit .) debounced on/off operation MAX5946 toc40 input_ 2v/div 10ms/div output_ 2v/div power-on-reset time vs. poradj resistor MAX5946 toc41 r poradj (k ? ) t por_hl (ms) 900 800 600 700 200 300 400 500 100 200 400 600 800 1000 1200 1400 1600 1800 2000 2200 2400 2600 2800 3000 0 01 000 t fault time delay vs. tim resistor MAX5946 toc42 r tim (k ? ) t fault (ms) 900 800 600 700 200 300 400 500 100 20 40 60 80 100 120 140 160 180 200 0 01 000
MAX5946 dual pci express, hot-plug controller 12 ______________________________________________________________________________________ pin name function 1 pres-deta present-detect input a. pres-deta accepts inputs from the prsnt#2 pin on a pci express connector. pres-deta has an internal pullup to 3.3vauxin. when pres-deta is low, the outputs follow the command from ona and auxona after a 4ms debounced time. when pres-deta goes from low to high, all outputs of the respective slot shut down with no delay (see table 2). 2 fona forced-on input a. fona has a 50k ? internal pullup to 3.3vauxin. a logic-low on fona turns on all slot a outputs as long as the power inputs are within their operating range, regardless of the status of the other input signals. leave fona open for normal operation (see table 2). 3 ona slot a 12v and 3.3v outputs enable. a logic-high at ona turns on the 12v and 3.3v outputs of slot a (see table 2). 4 auxona slot a 3.3v auxiliary output enable. a logic-high at auxona turns on the slot a auxiliary output (3.3vauxoa), see table 2. 5 12sa+ slot a 12v positive current-sense input. connect the positive terminal of the current-sense resistor to 12sa+ using the kelvin-sensing technique to assure accurate current sensing. 6 12sa- slot a 12v negative current-sense input. connect 12sa- to the negative side of the current-sense resistor using the kelvin-sensing technique to assure accurate current sensing. 7 12ga slot a 12v gate-drive output. connect 12ga to the gate of slot a? 12v mosfet. at power-up, v 12ga is raised to the internal charge-pump voltage level by a constant current. 83 .3sa+ slot a 3.3v positive current-sense input. connect the positive side of the current-sense resistor to 3.3sa+ using the kelvin-sensing technique to assure accurate current sensing. this input is also used for the 3.3v supply? uvlo function. 9 3.3sa- slot a 3.3v negative current-sense input. connect to the negative side of the sense resistor using the kelvin-sensing technique to assure accurate current sensing. 10 3.3ga s l ot a 3.3v g ate- d r i ve o utp ut. c onnect 3.3g a to the g ate of sl ot a s 3. 3v m os fe t. at p ow er - up , v 3 .3 ga i s ch ar g ed to 5.5v ab ove the 3.3v sup p l y b y a c onstant cur r ent d er i ved fr om v 1 2v in . 11 faulta open-drain fault output signal. faulta latches active low whenever the slot a outputs are shut down due to a fault. a fault is either of: ?an overcurrent condition lasting longer than the overcurrent timeout. ?a device over temperature condition. if the fault is detected in the main outputs, faulta must be reset by toggling the ona input. if the fault is in the auxiliary output, faulta must be reset by toggling both ona and auxona. for the auto- restart version, faulta is reset when the part initiates the next power-on cycle. 12 pwrgda open-drain power-good output. pwrgda goes low t por_hl after all outputs of slot a reach their final value and the power mosfets are fully enhanced. 13 3.3vauxoa slot a 3.3v auxiliary power-supply output 14 3.3vauxin 3.3v auxiliary supply input. 3.3vauxin is the input to a charge pump that drives the internal mosfets connecting 3.3vauxin to 3.3vauxoa and 3.3vauxob. v 3.3vauxin is also used to power the internal control logic and analog references of the MAX5946. 15 3.3vauxob slot b 3.3v auxiliary power output 16 pwrgdb slot b power-good output. see pwrgda function. 17 faultb slot b open-drain fault output. see faulta function. 18 3.3gb slot b 3.3v gate-drive output. see 3.3ga function. pin description
detailed description the MAX5946 dual hot-plug controller is designed for pci express applications. the device provides hot-plug control for 12v, 3.3v, and 3.3v auxiliary supplies of two pci express slots. the MAX5946? logic inputs/outputs allow interfacing directly with the system hot-plug-man- agement controller or through an smbus with an exter- nal i/o expander. an integrated debounced attention switch and present-detect signals are included to sim- plify system design. the MAX5946 drives four external n-channel mosfets to control the 12v and 3.3v main outputs. the 3.3v aux- iliary outputs are controlled through internal 0.24 ? n- channel mosfets. internal charge pumps provide a gate drive for the 12v outputs while the gate drive of the 3.3v output is driven by the 12v input supply. the 3.3v auxiliary outputs are completely independent from the main outputs with their own charge pumps. at power-up, the MAX5946 keeps all of the external mosfets off until all supplies rise above their respec- tive uvlo thresholds. the device keeps the internal mosfets off only until the 3.3vauxin supply rises above its uvlo threshold. upon a turn-on command, the MAX5946 enhances the external and internal mosfets slowly with a constant gate current to limit the power-supply inrush current. the MAX5946 actively limits the current of all outputs at all times and shuts down if an overcurrent condition persists for longer than a programmable overcurrent timeout. thermal- protection circuitry also shuts down all outputs if the die temperature exceeds +150 c. after an overcurrent or overtemperature fault condition, the MAX5946l latches off while the MAX5946a automatically restarts after a restart time delay. the power requirement for pci express connectors is defined by the pci express card specification and summarized in table 1. MAX5946 dual pci express, hot-plug controller ______________________________________________________________________________________ 13 pin name function 19 3.3sb- slot b 3.3v negative current-sense input. see 3.3sa- function. 20 3.3sb+ slot b 3.3v positive current-sense input. connect the positive side of the current-sense resistor to 3.3sb+ using the kelvin-sensing technique to assure accurate current sensing. 21 12gb slot b 12v gate-drive output. see 12ga function. 22 12sb- slot b 12v negative current-sense input. see 12sa- function. 23 12sb+ slot b 12v positive current-sense input. see 12sa+ function. 24 auxonb slot b 3.3v auxiliary output enable. see auxona function. 25 onb slot b 12v and 3.3v outputs enable. see ona function. 26 fonb slot b forced-on input. see fona function. 27 pres-detb slot b present-detect input. see pres-deta function. 28 tim overcurrent timeout programming input. connect a resistor between 500 ? and 500k ? from tim to gnd to program t fault . leave tim floating for a default timeout of 11ms. 29 input2 digital logic gate input 30 output2 digital output. 4ms debounced digital output of input2. 31 output1 digital output. 4ms debounced digital output of input1. 32 input1 digital logic gate input 33 12vin 12v supply input. v 12vin drives the gates of the mosfets connected to 3.3ga and 3.3gb. 12vin powers an internal charge pump that drives the gates of the mosfets connected to 12ga and 12gb. 34 gnd ground 35 pgnd power ground. connect externally to gnd. 36 poradj power-on-reset programming input. connect a resistor between 500 ? and 500k ? from poradj to gnd to program the por timing. leave floating for a default value of 160ms. pin description (continued)
MAX5946 dual pci express, hot-plug controller 14 ______________________________________________________________________________________ 5 a 12sa- 12ga 12sa+ 54mv 500mv r sense12a - + 150 a - + 50 a 3.3sa- 3.3ga 3.3sa+ 20mv 100mv control logic aux-slot a input comparators and chip-control logic control logic main-slot a charge pump t f ault oscillator t por oscillator r sense3.3a - + 150 a - + 10 a 100ma 10 a vref charge pump - + 150ma bias references and uvlo 5 a 12sb- 12gb 12sb+ 54mv 500mv r sense12b r tim r poradj 150 a 5 a 3.3sb- 3.3gb 3.3vauxob 3.3vauxoa 3.3vauxin ona pgnd gnd auxona fona pres-deta onb auxonb fonb pres-detb 3.3sb+ 20mv 100mv control logic aux-slot b control logic main-slot b charge pump debounce f ast oscillator 150 a vref charge pump r sense3.3b 10 a 100 a 10 a 150 a - + - + - + - + - + pwrgda faulta f aultb tim input1 output1 input2 output2 12vin poradj pwrgdb 10 a 100ma 10 a 150ma MAX5946 figure 1. functional diagram
startup the main supply outputs can become active only after all the following events have occurred: ? 3.3vauxin is above its uvlo threshold ? 12vin and v 3.3sa+ are both above their uvlo threshold on_ is driven high pres-det_ is low for more than 4ms the auxiliary supply output is made available only after the following events have occurred: ? 3.3vauxin is above its uvlo threshold auxon_ is driven high pres-det_ is low for more than 4ms the fon_ input overrides all other control signals and turns on the respective slot when driven low, as long as the uvlo thresholds have been reached. table 2 sum- marizes the logic conditions required for startup. the auxiliary supply input powers the internal control logic and analog references of the MAX5946, so the main supplies cannot be enabled if v 3.3vauxin is not present. when an output is enabled, a programmable startup timer (t su ) begins to count the startup time duration. the value of t su is set to 2x the fault timeout period (t fault ). r tim externally connected from tim to gnd sets the duration of t fault . MAX5946 dual pci express, hot-plug controller ______________________________________________________________________________________ 15 table 1. power requirements for pci express connectors power rail x1 connector x4/8 connector x16 connector 3.3v voltage tolerance ?% (max) ?% (max) ?% (max) supply current 3.0a (max) 3.0a (max) 3.0a (max) capacitive load 1000? (max) 1000? (max) 1000? (max) 12v voltage tolerance ?% (max) ?% (max) ?% (max) supply current 0.5a (max) 2.1a (max) 5.5a (max) capacitive load 300? (max) 1000? (max) 2000? (max) 3.3v auxiliary voltage tolerance supply current ?% (max) ?% (max) ?% (max) wake enabled 375ma (max) 375ma (max) 375ma (max) 375ma (max) 20ma (max) 20ma (max) 20ma (max) non-wake enabled, capacitive load 150? (max) 150? (max) 150? (max) table 2. control logic truth table on_ auxon_ fon_ pres-det_ 12v_ and 3.3v_ outputs 3.3vauxo_ auxiliary outputs xx low x on on xx high high off off low low high low* off off high low high low* on off low high high low* off on high high high low* on on * pres-det_ high-to-low transition has a 4ms delay (t deg ).
MAX5946 12v and 3.3v outputs normal operation the MAX5946 monitors and actively limits the current of the 12v and 3.3v outputs after the startup period. each output has its own overcurrent threshold. if any of the monitored output currents rise above the overcurrent threshold for a period t fault , fault_ asserts and the controller disengages both the 12v and 3.3v outputs for the particular slot (see the fault management section). 3.3v auxiliary output normal operation the auxiliary output current is internally monitored and actively limited to the maximum current-limit value. an overcurrent fault condition occurs when the output current exceeds the overcurrent threshold for longer then t fault . a fault on an auxiliary channel causes all supplies of the affected channel to be disabled after a programmable time period t fault (see the fault management section). power-good ( p p w w r r g g d d _ _ ) power-good ( pwrgd_ ) is an open-drain output that pulls low a time (t por_hl ) after all of the outputs of the respective slot are fully on. all outputs are considered fully on when 3.3g_ has risen to v pgth3.3 , 12g_ has risen to v pgth12 , and v 3.3auxo_ is less then v pgth3.3aux . t por_hl is adjustable from 2.5ms to 1.5s by connecting a resistor from poradj to gnd. see the setting the power-on-reset timeout period (t por ) section. thermal shutdown when the die temperature goes above (t sd ) +150?, an overtemperature fault occurs and the MAX5946 shuts down all outputs. the device waits for the junction temper- ature to decrease below t sd - hysteresis before entering fault management (see the fault management section). dual pci express, hot-plug controller 16 ______________________________________________________________________________________ v on_,th on_, auxon_ pwrgd_ f ault_ 12g_, 3.3g_ 12vo_, 3.3vo_ 3.3vauxo_ v pgth12 v pgth3.3 v pgth3.3aux 3.3auxin rising edge pwrgd_ is pulled up to 3.3. f ault_ is pulled up to 3.3auxin. t por_hl figure 2. power-up timing, no fault f ault_ 3.3vauxin rising edge pwrgd_ is pulled up to 3.3vauxo_. f ault_ is pulled up to 3.3vauxin. a fault on the 3.3v output or 3.3vauxo_ output produces similar results. v on_,th on_ 2 x t f ault pwrgd_ 12g_ 12v output current 3.3vauxo_ v 12ilim,th r sense figure 3. 12v power-up timing (turn-on into output overcurrent/short circuit) f ault_ pwrgd_ is pulled up to 3.3vauxo_. f ault_ is pulled up to 3.3vauxin. a fault on the 3.3v output or 3.3vauxo_ output produces similar results. t f ault pwrgd_ 12g_ 12v output current v 12ilim,th r sense figure 4. 12 output overcurrent/short circuit during normal operation
fault management a fault occurs when an overcurrent lasts longer then t fault or when the device experiences an overtemper- ature condition. ? fault on a main output (12v or 3.3v) shuts down both main outputs of the respective slot. the 3.3v auxiliary is not affected. ? fault on the 3.3v auxiliary output shuts down all three outputs of the respective slot. the MAX5946a automatically restarts from a fault shut- down after the t restart period, while the MAX5946l latches off. if an overcurrent fault occurred on a main output, bring on_ low for at least t reset (100?) and high again to reset the fault and restart the outputs. if the overcurrent fault occurred on an auxiliary output or an overtemperature fault occurred, bring both on_ and auxon_ low for a minimum of t reset to reset the fault. bring on_ and/or auxon_ high again to restart the respective outputs. as an extra protection, the MAX5946l waits a minimum of t restart before it can be restarted. debounced logic gate (input_ and output_) input1 and input2 accept inputs from mechanical switches. the corresponding outputs are output1 and output2. output_ is debounced for 4ms. when input_ goes from high to low, output_ goes low right away and stays low for at least 4ms. after the debounce time output_ follows input_. if input_ goes from low to high, output_ goes high right away and stays high for at least 4ms. after the debounce time, output_ follows input_. figure 5 shows the tim- ing diagram describing the input_/output_ debounced feature. present-detect and forced-on inputs ( p p r r e e s s - - d d e e t t _ _ , , f f o o n n _ _ ) pres-deta and pres-detb inputs detect the prsnt#2 pin on a pci express connector. when the card is plugged in, pres-det_ goes low and allows the turn-on of the outputs of the respective slot after a 4ms debounced time. when the card is removed, an internal 50k ? pullup forces pres-det_ high and the respective slot is shut down with no delay. pres-det_ works in conjunction with on_ and vauxon_ and only enables the device when on_ and vauxon_ are high. a logic-low on fon_ forces the respective slot (main supplies and auxiliary) to turn on regardless of the sta- tus of the other logic inputs provided the uvlo thresh- olds are exceeded on all of the inputs. active current limits active current limits are provided for all three outputs of slot a and slot b. connect a current-sense resistor between 12s_+ and 12s_- to set the current limit for the 12v outputs. the current limit is set to 54mv/r sense12 . r sense12 is either r1 or r3 in the typical application circuit . connect a current-sense resistor between 3.3s_+ and 3.3s_- to set the current limit for the 3.3v main outputs to 20mv/r sense3.3 . r sense3.3 is either r2 or r4 in the typical application circuit . for the auxiliary output (3.3v auxo_ ) the current limit is fixed at 470ma. when the voltage across r sense12 or r sense3.3 reaches the current-limit threshold voltage, the MAX5946 regulates the gate voltage to maintain the current-limit threshold voltage across the sense resis- tor. if the current limit lasts for t fault then an overcur- rent fault occurs. the MAX5946_ shuts down both the 12v and 3.3v outputs and asserts the fault_ output of the respective slot. when the auxiliary output reaches the current limit (470ma) for longer then t fault , a fault occurs and the device shuts down all outputs and asserts fault of the respective slot. undervoltage lockout threshold the uvlo thresholds prevent the internal auxiliary mosfets and the external main channel mosfets (q1?4 in the typical application circuit ) from turning on if v 12vin , v 3.3vin , and v 3.3vauxin are not present. internal comparators monitor the main supplies and the auxiliary supply and keep the gate-drive outputs (12ga, 12gb, 3.3ga, and 3.3gb) low until the supplies rise above their uvlo threshold. the 12v main supply is monitored at 12vin and has a uvlo threshold of 10v. the 3.3v main supply is monitored at 3.3sa+ and has a uvlo threshold of 2.65v. the auxiliary supply is monitored at 3.3vauxin and has a 2.65v uvlo thresh- old. for either main channel to operate, v 3.3vauxin must be above its uvlo threshold. MAX5946 dual pci express, hot-plug controller ______________________________________________________________________________________ 17 input debounced output t dbc t dbc t dbc figure 5. input_ and output_ debounced feature
MAX5946 dual pci express, hot-plug controller 18 ______________________________________________________________________________________ n y power-on main supplies fault and pwrgd are high impedance n enable charge on 12g_ and 3.3g_ pins. start counting t su has t su elapsed? n power-on auxiliary supplies fault and pwrgd are high impedance n enable charge on internal auxiliary mosfet, begin counting t su has t su elapsed? n y n y y are pwrgd thresholds reached? assert pwrgd_ after t por_hl delay 12v and 3.3v outputs are enabled w as current limit detected on any 12v or 3.3v output? start counting t f ault has t f ault elapsed? n y reset t f ault counter y shut down 12v and 3.3v outputs. assert fault_ stay waiting for t restart latch-off option? y stay waiting for on_ transition high->low->high aux supply output is enabled w as current limit detected on auxiliary output? is t f ault elapsed? n n y y shut down all outputs, assert fault_, stay waiting for t restart elapsed. latch-off option? y reset fault_ and restart all supplies stay waiting for both on_ and auxon_ transition high->low->high reset fault_ and restart 12v, 3.3v supplies is fault still present? y n is fault still present? n start counting t f ault reset t f ault counter reset pwrgd_ after t por_lh delay 3.3auxin is on and above uvlo figure 6. fault management flow chart
external mosfet gate drivers (12ga, 12gb, 3.3ga, and 3.3gb) the gate drive for the external mosfets is provided at 12ga, 12gb, 3.3ga, and 3.3gb. 12g_ is the gate drive for the 12v main supply and is boosted to 5.3v above v 12vin by an internal charge pump. during turn-on, 12g_ sources 5? into the external gate capacitance to control the turn-on time of the external mosfet. during turn-off, 12g_ sinks 150? from the external gate capacitance to quickly turn off the external mosfet. during short-circuit events, an internal 100ma current activates to rapidly bring the load current into the regu- lation limits. 3.3g_ is the gate drive for the 3.3v main supply? mosfet and is driven to 5.5v above the 3.3v main sup- ply. the power for 3.3g_ is supplied from 12vin and has no internal charge pump. during turn-on, 3.3g_ sources 5? into the external gate capacitance to con- trol the turn-on time of the external mosfet. during turn-off, 3.3g_ sinks 150? to quickly turn off the exter- nal mosfet. during short-circuit events, an internal 150ma current activates to rapidly turn off the appropri- ate external mosfet. auxiliary supply (3.3vauxin) 3.3vauxin provides power to the auxiliary outputs as well as the internal logic and references. the drains of the internal auxiliary mosfets connect to 3.3vauxin through internal sense resistors and the sources con- nect to the auxiliary outputs (3.3vauxoa and 3.3vauxob). both mosfets have typical on-resistance of 0.3 ? . an internal charge pump boosts the gate-drive voltage to fully turn on the internal n-channel mosfets. the auxiliary supplies have an internal current limit set to 470ma. applications information setting the fault timeout period (t fault ) t fault is the time an overcurrent or overtemperature fault must remain for the MAX5946 to disable the main or auxiliary channels of a particular slot. program the fault timeout period (t fault ) by connecting a resistor (r tim ) from tim to gnd. t fault can be calculated by the following equation: t fault = 166ns / ? x r tim the t fault programmed time duration must be chosen according to the total capacitance load connected to the 12g_ and 3.3g_ pins. to properly power-up the main supply outputs, the following constraints need to be taken: where t su = 2 x t fault and where 1) i chg = 5?. 2) v gate = 18.4v for 12g_ and v gate = 9.4v for 3.3g_. 3) c load is the total capacitance load at the gate. maximum and minimum values for r tim are 500 ? and 500k ? , respectively. leave tim floating for a default t fault of 11ms. setting the power-on-reset timeout period (t por_hl ) t por_hl is the time from when the gate voltages of all outputs of a slot reach their power-good threshold to when pwrgd_ pulls low. program the power-on-reset timeout period (t por ) by connecting a resistor (r po- radj ) from poradj to gnd. t por_hl can be calculat- ed by the following equation: t por_hl = 2.5? / ? x r poradj maximum and minimum values for r poradj are 500 ? and 500k ? , respectively. leave poradj floating for a default t por of 160ms. component selection select the external n-channel mosfet according to the applications current requirement. limit the switch power dissipation by choosing a mosfet with an r ds_on low enough to have a minimum voltage drop at full load. high r ds_on causes larger output ripple if there are pulsed loads. high r ds_on can also trigger an external undervoltage fault at full load. determine the mosfets power rating requirement to accommo- date a short-circuit condition on the board during start- up. table 3 lists mosfets and sense resistor manufacturers. additional external gate external capacitance can be added from the gate of the external mosfets to gnd to slow down the dv/dt of the 12v and 3.3v outputs. maximum load capacitance large capacitive loads at the 12v output, the 3.3v out- put, and the 3.3v auxiliary output can cause a problem when inserting discharged pci cards into live back- planes. a fault occurs if the time needed to charge the capacitance of the board is greater than the typical startup time (2 x t fault ). the MAX5946 can withstand t vc i su gate load chg MAX5946 dual pci express, hot-plug controller ______________________________________________________________________________________ 19
MAX5946 large capacitive loads due to their adjustable startup times and adjustable current-limit thresholds. calculate the maximum load capacitance as follows: v out is either the 3.3v output, the 12v output, or the 3.3v auxiliary output for slot a or slot b. input transients the 12v input (12vin), the 3.3v input (3.3sa+), and the 3.3v auxiliary (3.3vauxin) must be above their uvlo thresholds before startup can occur. input transients can cause the input voltage to sag below the uvlo threshold. the max5496 rejects transients on the input supplies that are shorter than 4? typical. chip information transistor count: 10,487 process: bicmos c ti v load su lim out < dual pci express, hot-plug controller 20 ______________________________________________________________________________________ table 3. component manufacturers component manufacturer phone website vishay-dale 402-564-3131 www.vishay.com sense resistor irc 704-264-8861 www.irctt.com fairchild 888-522-5372 www.fairchildsemi.com international rectifier 310-322-3331 www.irf.com motorola 602-244-3576 www.mot-sps.com/ppd/ mosfets vishay-siliconix www.vishay.com
MAX5946 dual pci express, hot-plug controller ______________________________________________________________________________________ 21 MAX5946 q1 si7448dp-t1 q3 si7448dp-t1 pwrgda 12ga 12sa- 12sa+ 3.3vauxin 12vin 112sb- 12sb+ 12gb 3.3vauxoa gnd pwrgdb 3.3vauxob poradj 10k ? prsnt1 +12v gnd pwrgd 3.3vaux +3.3v prsnt2 prsnt1 +12v gnd pwrgd 3.3vaux +3.3v prsnt2 v 3.3auxin r poradj = open v 3.3auxin r1 8m ? r3 8m ? r2 5m ? 10k ? r4 5m ? 0.1 f 0.1 f 10k ? q2 si7448dp-t1 q4 si7448dp-t1 3.3ga 3.3sa- 3.3sa+ auxona / auxonb ona / onb input1 / input2 output1 / output2 3.3sb+ tim 3.3sb- 3.3gb 3.3v input max7313atg 16-bit i/o expander mrl attention switches led's led's smbus int ao-2 2 2 r tm = open pres-deta pres-detb faulta / faultb fona / fonb 2 2 2 2 2 2 3 2 pci express slot a pci express slot b add-in card in5819 v 12vin mrl 1 f t ypical application circuit
MAX5946 dual pci express, hot-plug controller 22 ______________________________________________________________________________________ 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 .) 36l,40l, qfn.eps
MAX5946 dual pci express, hot-plug controller 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. maxim integrated products, 120 san gabriel drive, sunnyvale, ca 94086 408-737-7600 ____________________ 23 2004 maxim integrated products printed usa is a registered trademark of maxim integrated products. 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 .) u

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