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june 2000 1 mic2545a/2549a mic2545a/2549a micrel mic2545a/2549a programmable current limit high-side switch preliminary information general description the mic2545a and mic2549a are integrated high-side power switches optimized for low loss dc power switching and other power management applications, including advanced configuration and power interface (acpi). the mic2545a/ 49a is a cost-effective, highly integrated solution that re- quires few external components to satisfy usb and acpi requirements. load current management features include a precision resis- tor-programmable output current-limit and a soft-start circuit, which minimizes inrush current when the switch is enabled. thermal shutdown, along with adjustable current-limit, pro- tects the switch and the attached device. the mic2545a/49a? open-drain flag output is used to indi- cate current-limiting or thermal shutdown to a local controller. the mic2549a has an additional internal latch which turns the output off upon thermal shutdown, providing robust fault control. the enable signal is compatible with both 3v and 5v logic, and is also used as the thermal shutdown latch reset for the mic2549a. the mic2545a and mic2549a are available in active-high and active-low enable versions in 8-pin dip, soic, and tssop packages. typical application en flg gnd ilim out in out in mic2545a on/off peripheral 0.1f r set +5v 10k 33f typical advanced configuration and power interface (acpi) application features 2.7v to 5.5v input adjustable current-limit up to 3a reverse current flow blocking 90 a typical on-state supply current 1 a typical off-state supply current 50m ? maximum on-resistance open-drain fault flag thermal shutdown thermal shutdown output latch (mic2549a) 2ms (slow) soft-start turn-on, fast turnoff available with active-high or active-low enable applications usb power distribution pci bus power switching notebook pc acpi power distribution pc card hot swap applications inrush current-limiting micrel, inc. ?1849 fortune drive ?san jose, ca 95131 ?usa ?tel + 1 (408) 944-0800 ?fax + 1 (408) 944-0970 ?http://www.mic rel.com
mic2545a/2549a micrel mic2545a/2549a 2 june 2000 pin description pin number pin number pin name pin function sop, dip tssop 1 1 en enable (input): logic-compatible enable input (-1 version is active high, -2 version is active low). high input >1.8v typical; low input <1.4v typical. do not float. mic2549a only: also resets thermal shutdown latch. 2 3 flg fault flag (output): active-low, open-drain output. indicates overcurrent or thermal shutdown. mic2549a only: latched low on thermal shutdown. 3 5 gnd ground: supply return. 4 7 ilim current limit: sets current limit threshold using an external resistor (r set ) connected to ground. 76.8 ? < r set < 459 ? . 5, 7 8, 12 in supply input: output mosfet drain. also powers internal circuitry. both in pins must be externally connected together. 6, 8 10, 14 out switch output: output mosfet source. both out pins must be externally connected together. 2,4,6,9,11,13 nc not internally connected pin configuration 1 2 3 4 8 7 6 5 out in out in en flg gnd ilim mic2545a/2549a 8-lead sop (m) 8-pin dip (n) logic, charge pump 6,8 (out) 5,7 (in) (en) 1 (flg) 2 3 (gnd) (ilim) 4 mic2545a/2549a ordering information part number enable latch* temperature range package mic2545a-1bm active high 40 c to +85 c 8-lead sop mic2545a-1bn active high 40 c to +85 c 8-pin dip mic2545a-1bts active high 40 c to +85 c 14-lead tssop mic2545a-2bm active low 40 c to +85 c 8-lead sop mic2545a-2bn active low 40 c to +85 c 8-pin dip MIC2545A-2BTS active low 40 c to +85 c 14-lead tssop mic2549a-1bm active high 40 c to +85 c 8-lead sop mic2549a-1bn active high 40 c to +85 c 8-pin dip mic2549a-1bts active high 40 c to +85 c 14-lead tssop mic2549a-2bm active low 40 c to +85 c 8-lead sop mic2549a-2bn active low 40 c to +85 c 8-pin dip mic2549a-2bts active low 40 c to +85 c 14-lead tssop 2 nc 3 flg 4 nc 5 gnd 6 nc 7 ilim 1 en out 14 nc 13 in 12 nc 11 out 10 nc 9 8 in mic2545a/2549a 14-lead tssop (ts)
june 2000 3 mic2545a/2549a mic2545a/2549a micrel electrical characteristics v in = +5v; t a = 25 c, bold indicates 40 c to +85 c; unless noted symbol parameter condition min typ max units supply current switch off, out = open, note 4 0.75 5 a switch on, out = open, note 4 90 125 a 150 a v en enable input voltage enable high transition, note 4 2.4 1.6 v enable low transition, note 1 1.5 0.8 v enable input current v en = v oh(min) = 2.4v 0.01 1 a v en = v ol(max) = 0.8v 0.01 1 a enable input capacitance note 7 1pf r ds(on) switch resistance i out = 500ma 35 50 m ? current limit factor i limit = 0.5a to 3a, v out = 1v to 4v, note 5 160 230 300 v i limit = 1a to 2.5a, v out = 1v to 4v, note 5 184 230 276 v output leakage current switch off, v out = 0v 1 10 a t on output turn-on delay r l = 10 ? , c l = 1 f, figures 1a, 1b 125ms t r output turn-on rise time r l = 10 ? , c l = 1 f, figure 1a, 1b 0.75 1.8 4.9 ms t off output turnoff delay r l = 10 ? , c l = 1 f, figure 1a, 1b 25 s t f output turnoff fall time r l = 10 ? , c l = 1 f, figure 1a, 1b 23 s overtemperature threshold t j increasing 135 c shutdown t j decreasing 120 c error flag off current v flg = 5v 0.01 1 a en pulse reset width mic2549a thermal shutdown latch, note 7 1 s t su v in to en set-up mic2549a, note 7, figure 1c 0 s current-limit response time v out = 0v to i out = 2a, i set = 1a, note 7 40 s v ol error flag output resistance i flg = 10ma 4 15 ? 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 is 0.8v and on is 2.4v for the mic2545a-1 and mic2549a-1. off is 2.4v and on is 0.8v for the mic2545a-2 and mic2549a-2. the enable input has about 100mv of hysteresis. note 5. current limit is determined by: i r limit set = 230 , where r set is in ohms, and 230 is typical current limit factor in volts. note 6. assumes 4 layer pcb is used. note 7. guaranteed by design but not production tested. absolute maximum ratings (note 1) supply voltage (v in ) .................................................. +6.0v output voltage (v out ) ............................................... +6.0v output current (i out ) ............................... internally limited enable input (v en ) ......................................... 0.3v to +6v fault flag voltage (v flg ) ........................................... +6.0v fault flag current (i flg ) ............................................ 50ma storage temperature (t s ) ....................... 65 c to +150 c junction temperature (t j ) ....................... internally limited lead temperature (soldering 5 sec.) ........................ 260 c esd rating, note 3 .................................................. 2000v operating ratings (note 2) supply voltage (v in ) ................................... +2.7v to +5.5v ambient temperature range (t a ) ............. 40 c to +85 c package thermal resistance pdip ( ja ) ......................................................... 130 c/w soic ( ja ) ......................................................... 160 c/w tssop ( ja ), note 6 ........................................ 100 c/w current limit set range, note 5 ........................ 0.5a to 3a
mic2545a/2549a micrel mic2545a/2549a 4 june 2000 test circuit device under test c l out r l v out i out 90% v out 10% 90% 10% t r t f functional characteristics test circuit timing diagrams v en 50% 90% v out 10% t off t on figure 1a. mic2545a/49a-2 v en 50% 90% v out 10% t off t on figure 1b. mic2545a/49a-1 v in v en t su figure 1c. input-to-enable setup timing
june 2000 5 mic2545a/2549a mic2545a/2549a micrel en v out i out short-circuit fault thermal shutdown reached flg i limit i dc o utput r eset fault removed figure 2a. mic2549a-2 timing: output is reset by toggling en en v out i out short-circuit fault thermal shutdown reached fault removed flg i limit i dc figure 2b. mic2545a-2 timing
mic2545a/2549a micrel mic2545a/2549a 6 june 2000 typical characteristics 30 31 32 33 34 35 36 37 38 39 40 2.5 3.0 3.5 4.0 4.5 5.0 5.5 output resistance (m ? ) supply voltage (v) output on-resistance vs. supply voltage t a = 27 c 25 30 35 40 45 50 -40 -20 0 20 40 60 80 100 output resistance (m ? ) temperature ( c) output on-resistance vs. temperature 2.7v 3.3v 5.0v 0 20 40 60 80 100 120 140 2.5 3.0 3.5 4.0 4.5 5.0 5.5 supply current ( a) supply voltage (v) on-state supply current vs. supply voltage t a = 27 c 0 20 40 60 80 100 120 140 -40 -20 0 20 40 60 80 100 supply current ( a) temperature ( c) on-state supply current vs. temperature 2.7v 3.3v 5.0v 0 0.1 0.2 0.3 0.4 0.5 -40 -20 0 20 40 60 80 100 supply current ( a) temperature ( c) off-state supply current vs. temperature 2.7v 3.3v 5.0v r l = 44 ? 0 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09 0.10 2.5 3.0 3.5 4.0 4.5 5.0 5.5 supply current ( a) supply voltage (v) off-state supply current vs. supply voltage t a = 27 c 1.0 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 1.9 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 threshold volatage (v) supply voltage (v) control threshold voltage vs. supply voltage t a = 27 c high low 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 1.9 -40 -20 0 20 40 60 80 100 control threshold (v) temperature ( c) control threshold voltage vs. temperature low high 0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 -40 -20 0 20 40 60 80 100 output rise time (ms) temperature ( c) rise time vs. temperature 2.7v 3.3v 5.0v r l = 44 ? 0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 -40 -20 0 20 40 60 80 100 output fall time ( s) temperature ( c) output fall time vs. temperature 2.7v 3.3v r l = 44 ? 5.0v c l = 0 f 0 500 1000 1500 2000 2500 3000 3500 0 150 300 450 600 current limit (ma) r set ( ? ) current limit vs. rset i th v in = 5v i limit i short 0 500 1000 1500 2000 2500 3000 3500 0 1.0 2.0 3.0 4.0 5.0 6.0 output current (ma) output voltage (v) output current vs. output voltage r set = 92 v in = 5v r set = 230 r set = 460
june 2000 7 mic2545a/2549a mic2545a/2549a micrel 500 600 700 800 900 1000 1100 1200 1300 1400 1500 -40 -20 0 20 40 60 80 100 output current (ma) temperature ( c) current limit vs. temperature i th i set i short v in = 5v r set = 230 ? 600 700 800 900 1000 1100 1200 2.5 3.0 3.5 4.0 4.5 5.0 5.5 current limit (ma) supply voltage (v) current limit vs. supply voltage i th i set i short t a = 27 c r l = 230 ?
mic2545a/2549a micrel mic2545a/2549a 8 june 2000 functional characteristics turn-on response time (500 s/div.) mic2545a-1 i out (200ma/div.) v out (2v/div.) v en (10v/div.) v flg (10v/div.) 500ma v in = 5v c l = 100 f r l = 10 ? turnoff response time (1ms/div.) mic2545a-1 v in = 5v c l = 100 f r l = 10 ? 500ma i out (200ma/div.) v out (2v/div.) v en (10v/div.) v flg (10v/div.) current-limit response time (100ms/div.) mic2545a-1 i out (500ma/div.) v out (5v/div.) v en (10v/div.) v flg (10v/div.) load removed c = 5v r l = 1 ? current-limit threshold 1.12a (i th ) i set = 1a thermal shutdown short-circuit response time (100ms/div.) i out (500ma/div.) v out (5v/div.) v en (10v/div.) v flg (10v/div.) mic2545a-1 v in = 5v short circuit current-limit threshold 1.12a thermal shutdown short-circuit current 820ma (i short ) enable into short circuit time (100ms/div.) mic2545a-1 i out (500ma/div.) v out (5v/div.) v en (10v/div.) v flg (10v/div.) short-circuit current 820ma v in = 5v r set = 240 ? thermal shutdown inrush current response time (500 s/div.) mic2545a-1 v in = 5v r l = 10 ? i out (500ma/div.) v en (10v/div.) v flg (10v/div.) c l = 10 f c l = 130 f c l = 490 f
june 2000 9 mic2545a/2549a mic2545a/2549a micrel thermal shutdown (output reset by toggling enable mic2549-1) time (100ms/div.) i out (500ma/div.) v en (10v/div.) v out (5v/div.) v flg (5v/div.) thermal shutdown output reset ramped load to a short v in = 5v c l = 47 f output latched
mic2545a/2549a micrel mic2545a/2549a 10 june 2000 block diagram thermal shutdown osc. charge pump out gate control in flg en current limit gnd ilim r set thermal shutdown latch (mic2549a) reset in out 1.2v reference
june 2000 11 mic2545a/2549a mic2545a/2549a micrel functional description the mic2545a and mic2549a are high-side n-channel switches available with active-high or active-low enable in- puts. fault conditions turn off or inhibit turn-on of the output transistor and activate the open-drain error flag transistor making it sink current to ground. input and output in is the power supply connection to the logic circuitry and the drain of the output mosfet. out is the source of the output mosfet. in a typical circuit, current flows from in to out toward the load. if v out is greater than v in , current will flow from out to in since the switch is bidirectional when en- abled. the output mosfet and driver circuitry are also designed to allow the mosfet source to be externally forced to a higher voltage than the drain (v out > v in ) when the switch is disabled. in this situation, the mic2545a/49a avoids undesirable current flow from out to in. both in pins must be connected together, and both out pins must be con- nected together. thermal shutdown thermal shutdown shuts off the output mosfet and signals the fault flag if the die temperature exceeds 135 c. 10 c of hysteresis prevents the switch from turning on until the die temperature drops to 125 c. overtemperature detection functions only when the switch is enabled. the mic2549a features an internal latch which causes the part to remain off after thermal shutdown until a reset pulse is provided via the enable pin (pin 1). while in current-limit, the thermal shutdown latch prevents on/off cycling of the output. refer to figure 2 for timing diagram. the flag remains low until reset. enable input en must be driven logic high or logic low, or be pulled high or low for a clearly defined input. floating the input may cause unpredictable operation. en should not be allowed to go negative with respect to gnd. current-limit operation the current limit is user adjustable with an external set resistor. current limiting in the range of 500ma to 3a is available with a set point accuracy of better than 30% ( 20% for i set 1 to 2.5a). the current-limit circuit prevents damage to the output mosfet and external load. the current-limit response of the mic2545a/49a is based on the type of load that is applied to the output and is defined in three parts: 1. the first mode of operation is where the device enters a constant-current mode preventing further increases in output current. the value of this current, i limit , is defined by the value of r set as explained further in this section. 2. when a short circuit is applied to the output of an enabled device the output current immedi- ately folds back to a value less than i limit called i short . this further protects the load and reduces device power dissipation. refer to the typical characteristics: output current vs. output voltage graph for details. 3. when a load is increased, the output current will proportionally increase up to the current-limit threshold, i th , as shown in the functional characteristics: current-limit response graph. the device in this case will supply current slightly higher than the current-limit set point defined by r set . as the load is increased further the current folds back to i limit . the nominal current-limit value, i limit , is set with an external resistor between ilim (pin 4) and gnd (pin 3). for a desired current-limit, the value of the external set resistor is given by: r = i set limit 230 ? ? ? ? ? ? where: 76.8 ? < r set < 459 ? for example, to set a 1a nominal current-limit, r set is calculated as: 230 1a ? ? ? ? ? ? =? 230 refer to the typical characteristics: current-limit vs r set graph for more details. current through r set increases with output current. the voltage across r set could be monitored with a high imped- ance comparator to provide an indication of output current. r set should be between 76.8 ? and 459 ? (1% resister value). fault flag flg is an n-channel, open-drain mosfet output. the fault- flag is active (low) for current-limit or thermal shutdown conditions. the flag output mosfet is capable of sinking a 10ma load to typically 100mv above ground. for applications with v in 3.6v, it is recommended that flag current be limited to 5ma or less.
mic2545a/2549a micrel mic2545a/2549a 12 june 2000 applications information supply filtering a 0.1 f to 1 f bypass capacitor from in to gnd, located near the mic2545a and mic2549a, is strongly recommended to control supply transients. without a bypass capacitor, an output short may cause sufficient ringing on the input (from supply lead inductance) to damage internal control circuitry. input transients must not exceed the absolute maximum supply voltage (v in max = 6v) even for a short duration. mic2549a-1bm en out flg gnd out ilim in in 18 27 36 45 0.1f to 1f 4.0v to 5.5v r set figure 3. supply bypassing power dissipation the device's junction temperature depends on several fac- tors such as the load, pcb layout, ambient temperature and package type. equations that can be used to calculate power dissipation and junction temperature are found below. calculation of power dissipation can be accomplished by the following equation: p d = r ds(on) (i out )2 to relate this to junction temperature, the following equation can be used: t j = p d ja + t a where: t j = junction temperature t a = ambient temperature ja = is the thermal resistance of the package transient overcurrent filter the inrush current from the connection of a heavy capacitive load may cause the fault flag to fall for 10 s to 200 s while the switch is in a constant-current mode, charging the capaci- tance. adding an optional series resistor-capacitor (r set2 ) in paral- lel with r set , as shown in figure 4, allows the transient current-limit to be set to a different value than steady state. a typical usb hot-plug inrush is 2a to 3a for 10 s to 20 s. if r set is 435 ? (530ma), an r set2 of 88 ? (2.5a) and c set of 1 f (rc 90 s) allows transient surge of 3a to pass for 90 s without tripping the overcurrent flag (flg). usb power distribution the mic2545a is ideal for meeting usb power distribution requirements. figure 7 depicts a usb host application. r set should be set to a value providing a current-limit >500ma. the accurate current-limit of the mic2545a will reduce power supply current requirements. also, fast reaction to short circuit faults prevent voltage droop in mobile pc applications. printed circuit board hot-plug the mic2545a/49a is an ideal inrush current-limiter suitable for hot-plug applications. due to the integrated charge pump, the mic2545a/49a presents a high impedance when off and slowly becomes a low impedance as it turns on. this soft- start feature effectively isolates power supplies from highly capacitive loads by reducing inrush current during hot-plug events. figure 5 shows how the mic2545a may be used in a hot-plug application. on/off overcurrent mic2545a-2 3.3v usb controller v bus d+ d gnd 10k mic5203-3.3 ldo regulator in out gnd ferrite bead v bus d+ d gnd d+ d v+ en out flg in gnd out ilim in bold lines indicate 0.1" wide, 1-oz. copper high-current traces. downstream usb port 1 4.75v min. 500ma max. 120f 0.01f 1.0 f gnd 0.1f 5v (+) ( ) 4.7f r set r set(2) (optional) c set 1.5k 2% 0.1f figure 4. usb host application
june 2000 13 mic2545a/2549a mic2545a/2549a micrel mic2545a-2 en out flg gnd out in in 18 27 36 5 i lim 4 adaptor card to "hot" receptacle c bulk gnd v cc 0.1 f backend function 0.1f figure 5. hot-plug application
mic2545a/2549a micrel mic2545a/2549a 14 june 2000 package information 0.380 (9.65) 0.370 (9.40) 0.135 (3.43) 0.125 (3.18) pin 1 dimensions: inch (mm) 0.018 (0.57) 0.100 (2.54) 0.013 (0.330) 0.010 (0.254) 0.300 (7.62) 0.255 (6.48) 0.245 (6.22) 0.380 (9.65) 0.320 (8.13) 0.0375 (0.952) 0.130 (3.30) 8-pin dip (n) 45 0 8 0.244 (6.20) 0.228 (5.79) 0.197 (5.0) 0.189 (4.8) seating plane 0.026 (0.65) max ) 0.010 (0.25) 0.007 (0.18) 0.064 (1.63) 0.045 (1.14) 0.0098 (0.249) 0.0040 (0.102) 0.020 (0.51) 0.013 (0.33) 0.157 (3.99) 0.150 (3.81) 0.050 (1.27) typ pin 1 dimensions: inches (mm) 0.050 (1.27) 0.016 (0.40) 8-pin soic (m)
june 2000 15 mic2545a/2549a mic2545a/2549a micrel 1.10 max (0.043) 0.15 (0.006) 0.05 (0.002) 1.00 (0.039) ref 0.65 bsc (0.026) 8 0 6.4 bsc (0.252) 5.10 (0.200) 4.90 (0.193) 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) 0.30 (0.012) 0.19 (0.007) 14-pin tssop (ts)
mic2545a/2549a micrel mic2545a/2549a 16 june 2000 micrel inc. 1849 fortune drive san jose, ca 95131 usa tel + 1 (408) 944-0800 fax + 1 (408) 944-0970 web http://www.micrel.com this information is believed to be accurate and reliable, however no responsibility is assumed by micrel for its use nor for an y infringement of patents or other rights of third parties resulting from its use. no license is granted by implication or otherwise under any patent or pat ent right of micrel inc. ? 2000 micrel incorporated

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