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february 2005 1 mic2580a mic2580a micrel, inc. mic2580a hot-swap pci power controller general description the mic2580a is a hot-swap controller that provides for safe and orderly insertion and removal of pci based adapter cards from a pci hot-plug compliant system backplane or compactpci? system. the mic2580a incorporates a circuit breaker function that protects all four supplies (+12v, +5v, +3.3v, and C12v) upon an overcurrent fault condition. current foldback limiting pre- vents large transient currents caused by plugging adapter cards into live backplanes, such as in a compactpci system. a programmable slew-rate control limits high inrush currents to all loads that occur when power is applied to large capaci- tive loads. voltage supervisory functions for all four power supplies are provided by power good (/pwrgd) and overcurrent fault (/fault) diagnostic outputs. power good and overcurrent fault include deglitch filters to prevent nuisance tripping. power good is active when all four supplies are within tolerance. fault (/fault) goes active upon overcurrent or overtemperature conditions. the on-off control input (/on) is used to cycle power to the adapter card. t ypical application 12vout 5vgate 3vgate vpchg 12vin /fault gnd cstart /lpcirst 5vin 3vin /pcirst /epwrgd /on cslew mic2580a 5vsense 3vsense 5vout 3vout /por crst irf7413 irf7413 +3.3v +5v +12v /pwrgd m12vin m12vout +12v +5v +3.3v gnd C12v C12v 10m ? 10m ? v pch = +1v 20% (precharge supply) data bus /healthy /bd_sel /pci_rst vio C12v/1a gnd +3.3v/8a +5v/8a +12v/1a /enum data bus /on /pcirst /pgd adapter platform overcurrent f ault v io d0 d0 d1 d1 d2 d2 d n d n v io pci controller /lpcirst 1.2k 1 f 1 f 1 f 1 f compactpci? adapter with early power features ? pci hot-plug and compactpci? hot-swap support ? +12v, +5v, +3.3v, and C12v power supply control ?c ircuit breaker function to protect system ?p rogrammable slew rate control for all supplies ? foldback current-limiting ? +5v and +3.3v programmable current-limit thresholds ? undervoltage and overcurrent diagnostic outputs ? deglitch filters on diagnostic fault outputs ?i ntegrated +12v and C12v mosfet switches ?i ntegrated high-side drivers for 3.3v and 5v external switches ?p recharge supply for compatpci? i/o termination applications ? pci hot-plug systems ? compactpci? hot-swap systems micrel, inc. ? 2180 fortune drive ? san jose, ca 95131 ? usa ? tel + 1 (408) 944-0800 ? fax + 1 (408) 474-1000 ? http://www.mic rel.com compactpci is a trademark of the pci industrial computer manufacturers group.
mic2580a micrel, inc. mic2580a 2 february 2005 pin configuration 1 12vout 3vgate 3vout 3vsense 3vin /pcirst /lpcirst /epwrgd /pwrgd vpchg 24 12vin 5vgate 5vout 5vsense 5vin /fault cstart cslew /por crst 23 22 21 20 19 18 17 16 15 2 3 4 5 6 7 8 9 10 gnd /on 11 m12vin m12vout 12 14 13 24-lead tssop (ts) pin description pin number pin name pin function 1 12vout +12v switched supply (output): load carrying output. 2 3vgate 3.3v gate drive (output): drives gate of external n-channel mosfet +3v switch. adding capacitance will slow the slew rate of the external mosfet switch turn-on. (the external mosfets gate is charged by an internal current source.) 3 3vout +3.3v output voltage sense (input): connect to source of external n-channel mosfet (+3v switched output) to monitor for output undervolt- age conditions. 4 3vsense +3.3v current sense (input): measures voltage drop across an external sense resistor with respect to 3vin for overcurrent detection through the +3.3v switch. 5 3vin 3v supply (input): +3.3v-supply input for current monitoring (reference input for 3vsense). not a load-current carrying input. 6 /pcirst pci-bus reset (input): input from pci bus that resets the internal logic. ordering information part number precharge temperature standard pb-free voltage range package mic2580a-1.0bts mic2580a-1.0yts 1v C40 c to +85 c 24-lead tssop mic2580a-1.6bts mic2580a-1.6yts 1.6v C40 c to +85 c 24-lead tssop
february 2005 3 mic2580a mic2580a micrel, inc. pin number pin name pin function 7 /lpcirst local pci reset (open-drain output): local pci reset output to pci controller. compliant to compactpci specification for local_pci_reset. 8 /epwrgd early power good (open-drain output): this signal goes active should /fault or /pwrgd go active. no deglitch filtering is provided. this signal satisfies pci /rst timing for t fail per pci local bus specification, ver- sion 2.1. 9 /pwrgd power good (open-drain output): active-low output goes active when all supplies are within tolerance. (a 20 s delay is inserted prior to activation to reduce nuisance tripping.) 10 vpchg precharge supply (output): (mic2580a-1.0) +1v 20% supply used for precharge bias for i/o terminations (compactpci only). 11 gnd ground 12 m12vin C12v supply (input): input for internal C12v switch. 13 m12vout C12v switched supply (output): switched C12v supply to pci hot plug compliant socket. load carrying output. 14 /on on-off control (input): logic low turns on all switches; logic high turns off all switches. also used to reset the device from a circuit breaker condition. the /on pin is edge-triggered and requires a high-to-low transition once all four supplies are above their respective thresholds. 15 crst reset delay (external component): connect to external capactior (c rst ) to increase power-on reset delay. 16 /por reset (open-drain output): active-low signal remains active for a time determined by c rst after all supplies are within tolerance; i.e., /pwrgd is active. this signal may be used as a reset for logic controllers. 17 cslew slew (external component): connect to external capacitor (c slew ) to program the output slew rate of 3vgate, 5vgate, 12vgate (internal) and m12vgate (internal). 18 cstart start-up timer (external component): connect to external capacitor (c start ) to increase the filter delay used to gate the /fault output upon start-up. used to prevent nuisance tripping during turn-on of supplies. 19 /fault fault (open-drain output/input): this active-low output signal activated upon overcurrent or thermal shutdown. includes 20 s deglitch filter. fault is reset using /on. forcing pin low turns off all switches but does not activate the circuit breaker function. 20 5vin 5v supply (input): +5v-supply input for current monitoring (reference voltage for 5vsense). not a load-current carrying input. 21 5vsense +5v current sense (input): measures voltage drop across an external sense resistor with respect to 5vin for overcurrent detection through the +5v switch. 22 5vout +5v output voltage sense (input): connect to source of external n-channel mosfet (+5v switched output) to monitor for output undervoltage condi- tions. 23 5vgate 5v gate drive (output): drives gate of external n-channel mosfet +5v switch. adding capacitance will slow the slew rate of the external mosfet switch turn-on. (the external mosfets gate is charged by an internal current source.) 24 12vin 12v supply (input): mic2580a power supply and input for internal +12 switch. supplies power for internal circuitry.
mic2580a micrel, inc. mic2580a 4 february 2005 absolute maximum ratings (note 1) supply voltages +12v input (v 12vin ) ................................................. +14v +5v input (v 5vin ) ....................................................... +7v +3.3v input (v 3vin ) .................................................... +7v C12v input (v m12vin ) ............................................... C14v /pwrgd, /fault, /por, /epwrgd, and /pcirst output current ........................................................... 10ma lead temperature (soldering) standard package (-x.xbts) ir reflow ......................................... 240 c + 0oc/-5oc lead-free package (-x.xyts) ir reflow ......................................... 260oc + 0oc/-5oc esd rating, note 3 human body model ................................................... 2kv operating ratings (note 2) supply voltages +12v input (v 12vin ) ............................. +11.4v to +12.6v C12v input (v m12vin ) ........................... C11.4v to C12.6v +5v input (v 5vin ) ................................... +4.75v to +5.25 +3.3v input (v 3vin ) .............................. +3.125v to +3.5v temperature range (t a ) ........................... C40 c to +85 c junction temperature (t j ) ........................................ 150 c package thermal resistance ( ja ) 24-lead tssop .................................................. 83 c/w electrical characteristics v 12vin = 12v, v 5vin = 5v, v 3vin = 3.3v, v m12vin = C12v; t a = 25 c, bold values indicate C40 c t a +85 c; unless noted symbol parameter condition min typ max units i 12in supply current /on > v ih 2.2 3 ma i 5in 46ma i 3in 0.23 0.4 ma i 12min 35ma v uvlo undervoltage lockout v 12vin increasing 8.9 9.8 v v 12vin uvlo hysteresis 300 mv v m12vin decreasing -10.5 -8.3 v v m12vin uvlo hysteresis 100 mv v 5vin increasing 2.1 3.1 v v 5vin uvlo hysteresis 20 mv v 3vin increasing 2.4 2.6 v v 3vin uvlo hysteresis 60 mv v 5vgate 5vgate voltage 10.5 11 v v 3vgate 3vgate voltage 10.5 11 v i 5vgate 5vgate output current during start-up, v 5vgate = 5v C40 a during turnoff; /fault = 0 6 ma i 3vgate 3vgate output current during start-up, v 5vgate = 5v C40 a during turnoff; /fault = 0 6 ma v pgth power good threshold voltage v 12vout increasing 11 11.4 v v 12vout power-good hysteresis 200 mv v m12vout decreasing C11.2 C10 v v m12vout power-good hysteresis 50 mv v 5vout increasing 4.45 4.7 v v 5vout power-good hysteresis 100 mv v 3vout increasing 2.90 3.10 v v 3vout power-good hysteresis 60 mv v il input voltage level (/on) logic low 0.8 v v ih logic high 2.0 v i il input leakage currnet (/on) C1 1 a
february 2005 5 mic2580a mic2580a micrel, inc. symbol parameter condition min typ max units v ol output-low voltage i ol = 2ma 0.4 v (/pwrgd, /fault, /por, epwrgd, /lpcirst) t ov overtemperature shutdown t j increasing 170 ?c threshold t j decreasing 160 ?c i crst crst charge current during turn-on C9 C11.5 a i cstart cstart charge current during turn-on C9 C11.5 a i cslew cslew charge current during turn-on C30 C39 C45 a r ds(on)12 output mosfet resistance +12v internal mosfet, i ds = 500ma 450 600 m ? r ds(on)m12 C12v internal mosfet, i ds = 200ma 430 600 m ? output mosfet leakage +12v internal mosfet C100 100 a C12v internal mosfet 0 300 a v clth current limit threshold voltage v 5vin C v 5vsense 45 56 67 mv v 3vin C v 3vsense 45 55 67 mv i lim12 current-limit +12v internal mosfet, ramped load 1.0 1.3 1.5 a i lim12m threshold C12v internal mosfet, ramped load C0.4 C0.5 C0.7 a short-circuit current +12v internal mosfet, v out = 0v 140 ma C12v internal mosfet, v out = 0v C170 ma v por(thr) power-on reset threshold voltage 2.4 v v pch precharge bias supply mic2580a-1.0, i pch = 10ma 0.8 1.0 1.2 v mic2580a-1.6, i pch = 10ma 1.28 1.6 1.92 v v start start-up threshold voltage 2.4 v ac parameters t good early power-good see figure 4 200 ns response low t /good early power-good see figure 4 100 ns response high undervoltage to power-good delay 20 s current-limit to fault delay 20 s +5v current-limit-to-off delay v sense = 10m ? 7 s note 4 +3.3v current-limit-to-off delay v sense = 10m ? 7 s note 4 +12v current-limit-to-off delay +12v 25 s note 4 C12v current-limit-to-off delay C12v 25 s note 4 note 1. exceeding the absolute maximum rating may damage the device. note 2. the device is not guaranteed to function outside its operating rating. note 3. devices are esd sensitive. handling precautions recommended. human body model, 1.5k in series with 100pf. note 4. off refers to the condition in which the circuit breaker turns all outputs off.
mic2580a micrel, inc. mic2580a 6 february 2005 /on +5v 0v 0v 5vout short circuit +3.3v 3vout 0v +12v 12vout C12v 0v m12vout /pwrgd t start /fault /por ti ming diagrams figure 1. controller timing: normal cycle figure 2. controller timing: enable into short figure 3. controller timing: short on 5v /on +5v 0v 0v 5vout +3.3v 3vout 0v +12v 12vout C12v 0v m12vout /pwrgd /fault /por t reset /on +5v 0v 0v 5vout +3.3v 3vout 0v +12v 12vout C12v 0v m12vout /pwrgd /fault f ault circuit breaker reset figure 4. early power good response time +5v 0v /epwrgd t /good t good v in v pgth } 1v
february 2005 7 mic2580a mic2580a micrel, inc. t ypical characteristics 100x10 -6 1x10 -3 10x10 -3 100x10 -3 0.001 0.01 0.1 time (s) c por ( f) power-on reset time 100x10 -6 1x10 -3 10x10 -3 100x10 -3 0.0001 0.001 0.01 0.1 time (s) c slew ( f) output rise time vs. slew-rate capacitance 10x10 -6 100x10 -6 1x10 -3 10x10 -3 100x10 -3 0.0001 0.001 0.01 0.1 time (s) c start ( f) start-up time
mic2580a micrel, inc. mic2580a 8 february 2005 functional characteristics 12vout 5vgate 3vgate vpchg 12vin /fault gnd cstart /lpcirst 5vin 3vin /pcirst /epwrgd /on cslew mic2580a 5vsense 3vsense 5vout 3vout /por crst irf7413 irf7413 /pwrgd m12vin m12vout +12v +5v +3.3v 2.2k 2.2k 10m ? 10m ? c 12l c 5l c 3l r 12l r 5l r 3l c rst c start c m12l r m12l c slew 2.2k +5v C12v 2.2k functional test circuit
february 2005 9 mic2580a mic2580a micrel, inc. 3v and 5v gate-voltage response time (2.5ms/div) v /on (5v/div) v cslew (5v/div) v 3vgate (5v/div) v 5vgate (5v/div) power- on reset response t reset = 2.6ms time (1ms/div) v /on (10v/div) v /pwrgd (5v/div) v crst (2v/div) v /por (5v/div) po wer-good response time (10 s/div) v /epwrgd (5v/div) v /pwrgd (5v/div) c rst = 0.01 f c slew = 0.03 f c start = 0.01 f c rst = 0.01 f
mic2580a micrel, inc. mic2580a 10 february 2005 c rst = 0.01 f f ault response v /on (10v/div) v /fault (10v/div) time (10ms/div) v 3vout (5v/div) v 5vout (5v/div) v 12vout (10v/div) v m12vout (10v/div) pull /fault low
february 2005 11 mic2580a mic2580a micrel, inc. v /pwrgd (5v/div) tu rn-on and turn-off v /on (10v/div) v 3vout (5v/div) v 5vout (5v/div) v 12vout (10v/div) v m12vout (10v/div) v /por (5v/div) v /fault (5v/div) time (2.5ms/div) -12v turn-on v /on (10v/div) v cstart (5v/div) v m12vout (10v/div) i m12vin (100ma/div) v /pwrgd (5v/div) v /por (5v/div) v /fault (5v/div) time (2.5ms/div) 150ma c start = 0.01 f c slew = 0.03 f c rst = 0.01 f c start = 0.01 f c slew = 0.07 f c rst = 0.01 f c m12l = 1 f r m12l = 80 ?
mic2580a micrel, inc. mic2580a 12 february 2005 3v turn-on v /on (10v/div) v cstart (5v/div) v 3vout (2v/div) i 3vin (1a/div) v /pwrgd (5v/div) v /por (5v/div) v /fault (5v/div) time (2.5ms/div) 1.5a 0.6a/ms 5v turn-on v /on (10v/div) v cstart (5v/div) v 5vout (5v/div) i 5vin (1a/div) v /pwrgd (5v/div) v /por (5v/div) v /fault (5v/div) time (2.5ms/div) 1.5a 0.375a/ms c start = 0.01 f c slew = 0.03 f c rst = 0.01 f c 3l = 100 f r 3l = 2.2 ? c start = 0.01 f c slew = 0.03 f c rst = 0.01 f c 5l = 100 f r 5l = 3.3 ?
february 2005 13 mic2580a mic2580a micrel, inc. 12v turn-on v /on (10v/div) v cstart (5v/div) v 12vout (10v/div) i 12vin (100ma/div) v /pwrgd (5v/div) v /por (5v/div) v /fault (5v/div) time (1ms/div) 150ma enable into -12v output short circuit v /on (10v/div) v cstart (5v/div) v 3vout (5v/div) i m12vin (200ma/div) v m12vout (10v/div) v 12vout (10/div) v 5vout (5v/div) v /por (5v/div) v /fault (5v/div) v /pwrgd (5v/div) time (1ms/div) c start = 0.01 f c slew = 0.04 f c rst = 0.01 f c 12l = 1 f r 12l = 80 ? c start = 0.01 f c slew = 0.01 f c rst = 0.01 f r 12l = 100 ? c 12l = 1 f m12vout = gnd
mic2580a micrel, inc. mic2580a 14 february 2005 enable into 3v output short circuit v /on (10v/div) v cstart (5v/div) v 3vout (5v/div) v m12vout (10v/div) v 12vout (10v/div) i 3vin (1a/div) v 5vout (5v/div) v /pwrgd (5v/div) v /por (5v/div) v /fault (5v/div) time (1ms/div) enable into 5v output short circuit v /on (10v/div) v cstart (5v/div) v 3vout (5v/div) v 12vout (10v/div) v m12vout (10v/div) v 5vout (5v/div) i 5vin (200ma/div) v /pwrgd (5v/div) v /por (5v/div) v /fault (5v/div) time (1ms/div) c start = 0.01 f c slew = 0.01 f c rst = 0.01 f 3vout = gnd r 12l = 100 ? c 12l = 1 f r m12l = 100 ? c m12l = 1 f c start = 0.01 f c slew = 0.01 f c rst = 0.01 f r 12l = 100 ? c 12l = 1 f r m12l = 100 ? c m12l = 1 f 5vout = gnd
february 2005 15 mic2580a mic2580a micrel, inc. enable into 12v output short circuit v /on (10v/div) v cstart (5v/div) v 3vout (5v/div) v m12vout (10v/div) v 12vout (10v/div) v 5vout (5v/div) i 12vin (500ma/div) v /pwrgd (5v/div) v /fault (5v/div) time (1ms/div) v /por (5v/div) start-up blanking response v /on (10v/div) v cstart (5v/div) i 5vin (200ma/div) v 5vout (5v/div) v /pwrgd (5v/div) v /por (5v/div) v /fault (5v/div) time (1ms/div) short removed c start = 0.01 f c slew = 0.01 f c rst = 0.01 f c 12l = 1 f r m12l = 100 ? c m12l = 1 f 12vout = gnd c start = 0.01 f c slew = 0.01 f c rst = 0.01 f
mic2580a micrel, inc. mic2580a 16 february 2005 circuit breaker reset response on# (10v/div) 3vout (5v/div) m12vout (10v/div) 12vout (10v/div) 5vout (5v/div) pwrgd# (5v/div) por# (5v/div) faul t# (5v/div) time (10ms/div) circuit breaker new start cycle short circuit c start = 0.01 f c slew = 0.01 f c rst = 0.01 f
february 2005 17 mic2580a mic2580a micrel, inc. functional diagram 12v switch 5v switch control thermal shutdown t d = 20 s (delay) C12v switch t d = 20 s (delay) slew control current limit control logic and power good precharge supply 3.3v switch control 12vout 5vgate 3vgate vpchg 12vin m12vout /pwrgd /lpcirst 5vin 3vin cslew /on m12vin /pcirst mic2580a /epwrgd /fault cstart 5vsense 3vsense 5vout 3vout /por gnd crst c rst c slew r 5sns r 3sns q 5out q 3out reset c start
mic2580a micrel, inc. mic2580a 18 february 2005 functional description start-up sequence the start-up sequence iniates after all four supplies are connected to the inputs and then /on is asserted by transistioning from high to low. during the start-up sequence, all four gates ramp up at a rate determined by c slew . during this time /pwrgd is deasserted until all four supplies are within specified levels. when /pwrgd is asserted the power- on-reset signal /por timer begins. the time period is defined by c rst . refer to figure 1 for a timing diagram of the signals during the start-up sequence. during the start-up sequence, a current source charges c start at a constant rate until a threshold voltage of 2.4v is reached. this period of time defines an interval during which overcurrent events are ignored. this prevents high inrush currents that normally occur when charging capacitance erroneously asserting /fault. the magnitude of the start- up time, t start is defined by c start . the mic2580a employs foldback current limiting that en- sures the device starts up in current limit. this minimizes high inrush currents due to ramping a voltage into capacitance regardless of the size of the load capacitance. overcurrent detection the mic2580a senses overcurrent via the use of external sense resistors for the 5v and 3.3v supply rails. when the sense voltage across these resistors is greater than or equal to 50mv an overcurrent condition is detected. therefore the overcurrent set point is determined by i limit = 50mv/r sense . for the +12v and C12v supply rails overcurrent detection is set internally at 1.3a and C0.5a respectively. when an overcurrent condition is detected /fault is as- serted only if the overcurrent condition lasts for a minimum time period of 10 s. this delay prevents spurious noise from the system erroneously tripping the circuit breaker and as- serting /fault. upon /fault being asserted an internal latch is set that immediately turns off all four supplies to prevent further damage to the system. toggling /on will reset the latch and initiate another start-up sequence. figures 2 and 3 depict the timing for two fault conditions. thermal shutdown the +12v and C12v internal mosfet switches are protected by current limit and overtemperature shutdown circuitry. when the die temperature exceeds 160 c, /fault is as- serted and all supplies are shut off. the power dissipated in the mic2580a is primarily due to the sum of current flowing through the internal mosfet switches and, to a lesser extent, power dissipated due to the supply current. to com- pute the total power dissipation of the mic2580a the follow- ing equation is used: p d(total) = p d(+12v switch) + p d(C12v switch) + p d(supplies) where: p d(switches) = r ds(on) i out 2 p d(supplies) = v supply i supply to relate this to operating junction temperature: t j = p d ja + t a where: t a = ambient temperature ja = package thermal resistance precharge voltage for compactpci applications, the mic2580a-1.0bsm/bts integrates a 1v 20% voltage source that satisfies compactpci precharge requirements. the voltage source can provide up to 10ma. for higher current, the mic2580a- 1.6bsm/bts integrates a 1.6v 20% voltage source to bias a npn transistor. mic2580a-1.6 vpchg d ata bus r i > 10ma +5v figure 5. voltage source turnoff deasserting /on will turn off all four supplies. alternatively driving /fault low will turn off all supplies but will not latch the supplies off. releasing /fault will initiate a new start sequence.
february 2005 19 mic2580a mic2580a micrel, inc. application information whenever voltage is applied to a highly capacitive load, high inrush currents may result in voltage droop that may bring the supply voltage out of regulation for the duration of the transient. the mic2580a solves this problem by specifically controlling the current and voltage supply ramps so that the system supply voltages are not disturbed. very large capaci- tive loads are easily supported with this device. figure 1 shows the timing during turn-on. when /on is forced low, all supplies are turned on at a slew rate determined by the external capacitor, c slew . figure 2 shows the foldback characteristics for the supply voltages. this foldback affect bounds the magnitude of the current step when the supplies are turned on or shorted. this specifies the compact pci specification of 1.5a/ms, thereby ensuring reliable operation. in discrete fet implementa- tions, this magnitude can exceed several amps and may cause the main supply to go out of regulation during this transient event. this, in turn, could cause the system to behave unpredictably. in addition, should a fault occur, the mic2580a will prevent system malfunctions by limiting the current to within specifications. mosfet selection the external mosfet should be selected to provide low enough dc loss to satisfy the applications voltage regulation requirements. note that the voltage across the sense resistor must also be added to the dc voltage drop across the mosfet to compute total loss. in addition to meeting the voltage regulation specifications, thermal specifications must also be considered. during normal operation very little power should be dissipated in the mosfet. dc power dissipation of the mosfet is easily computed as i 2 r ds where i is the drain current and r ds is the specified on-resistance of the mosfet at the expected operating drain current. however, during excessive drain current or short-circuit faults, the power dissipation in the external mosfet will increase dramatically. to help compute the effective power dissipated during such transients, mosfet manufacturers provide transient thermal impedance curves for each mosfet. these curves provide the effective thermal impedance of the mosfet under pulsed or repetitive conditions; for example, as will be the case when enabling into a short circuit fault. from these curves the effective rise in junction temperature of the mosfet for a given condition can be computed. the equation is given as: peak t j = pdm z ja + t a where pdm is the power dissipated in the mosfet usually computed as v in x i drain and z ja is the thermal response factor provided from the curves. since the mic2580a re- duces the current to 30% of full scale even under severe faults such as short-circuits the mosfet power dissipation is held to safe levels. this feature allows mosfets with smaller packages to be used for a given application thereby reducing cost and pcb real-estate requirements. 12vout 5vgate 3vgate vpchg 12vin /fault gnd cstart /lpcirst 5vin 3vin /pcirst /epwdgd /on cslew mic2580a 5vsense 3vsense 5vout 3vout crst irf7413 irf7413 3.3v 5v 12v /pwdgd m12vin m12vout +12v +5v +3.3v gnd C12v power supply /cirst b us en C12v /cirst data bus /cirst C12v /100ma 12v/500ma 5v/5a 3.3v/7.6a 10m ? 10m ? pci hot-plug controller bus switch data bus gnd adapter platform /por d0 d0 +5v d1 d1 d2 d2 d n d n figure 6. hot-plug pci application
mic2580a micrel, inc. mic2580a 20 february 2005 compactpci? bd_sel# pin tied to ground for applications that use system backplanes with the bd_sel# pin tied to ground, the mic2580a /on pin is edge sensitive. therefore, the /on pin requires a delay circuit for proper start-up when the board has already been inserted into the backplane and the supplies are switched off, then back on. the circuit, shown in the figure below, allows the mic2580a /on pin to transition from high to low which is necessary for start-up. the delay time may be increased or decreased by changing the rc time constant in the circuit, but the delay time must exceed the ramp time of all system backplane supplies. the same circuit is functional for hot swap insertion. v io (3.3v or 5v) 3.3 f /fault /reset mic2580a /on 1.2k 10k 50k 2n3904 1n914 2k 2k bd_sel# on pcb figure 7. /on pin assertion delay circuit pcb layout considerations to achieve accurate current sensing kelvin connections are recommended between the supply pin and the respective sense resistor as shown in figure 8. pcb trace length should be kept at a minimum. 0.02 inches per ampere is a minimum width for 1 oz. copper to prevent damage to traces carrying high current. keep these high-current traces as short as possible. to vin pin from supply to sense pin to load sense resistor kelv in connections short-length, high-current (wide) copper traces figure 8. layout recommendation
february 2005 21 mic2580a mic2580a micrel, inc. package information 1.10 max (0.043) 0.15 (0.006) 0.05 (0.002) 1.00 (0.039) ref 8 0 6.4 bsc (0.252) 7.90 (0.311) 7.70 (0.303) 0.30 (0.012) 0.19 (0.007) 0.20 (0.008) 0.09 (0.003) 0.70 (0.028) 0.50 (0.020) dimensions: mm (inch) 4.50 (0.177) 4.30 (0.169) 0.65 bsc (0.026) 24-lead tssop (ts) micrel inc. 2180 fortune drive san jose, ca 95131 usa tel + 1 (408) 944-0800 fax + 1 (408) 474-1000 web http://www.micrel.com this information furnished by micrel in this data sheet is believed to be accurate and reliable. however no responsibility is a ssumed by micrel for its use. micrel reserves the right to change circuitry and specifications at any time without notification to the customer. micrel products are not designed or authorized for use as components in life support appliances, devices or systems where malfu nction of a product can reasonably be expected to result in personal injury. life support devices or systems are devices or systems that (a) are intend ed for surgical implant into the body or (b) support or sustain life, and whose failure to perform can be reasonably expected to result in a significant inj ury to the user. a purchasers use or sale of micrel products for use in life support appliances, devices or systems is a purchasers own risk and purchaser a grees to fully indemnify micrel for any damages resulting from such use or sale. ? 2001 micrel incorporated

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