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march 2000 1 mic2536 mic2536 micrel mic2536 dual usb power distribution switch final information general description the mic2536 is a cost-effective high-side power switch, with two independently controlled channels, optimized for bus- powered universal serial bus (usb) applications. few exter- nal components are necessary to satisfy usb requirements. each switch channel of the mic2536 will supply up to 100ma as required for usb bus-powered downstream devices. fault current is limited to typically 275ma by fast-acting current- limit circuitry which minimizes voltage droop on the upstream port during fault conditions. a flag output with transient filter indicates fault conditions to the local usb controller but will ignore short flag signals resulting from inrush current during hot plug-in events. soft start eliminates the momentary voltage droop on other ports that may occur when the switch is enabled in bus- powered applications. additional features include thermal shutdown to prevent catastrophic switch failure from high- current loads and 3.3v and 5v logic compatible enable inputs. the mic2536 is available in active-high and active-low ver- sions in 8-lead sop and msop. typical application ena outa flga in flgb gnd enb outb mic2536-2 3.3v usb controller 0.1? v bus d+ d gnd data (two pair) v bus d+ d gnd usb port 2 usb port 1 mic5207-3.3 63f 63f ferrite beads 4.50v to 5.25v upstream v bus 100ma max. v bus d+ d gnd data 4.7f 1f to usb controller 1.5k on/off overcurrent overcurrent on/off vin 10k in out gnd .01f .01f 10k typical two-port bus-powered hub features compliant to usb specifications 2.7v to 5.5v operating range 150ma minimum continuous load current per channel 400m ? typical on-resistance fast-acting short circuit protection with thermal shutdown integrated filter eliminates false overcurrent flag assertions individual open-drain fault flag pins with transient filter 3v/5v-compatible enable inputs active-high (-1) and active-low (-2) versions reverse-current blocking in off mode (no body diode ) soft-start circuit 100 a maximum on-state supply current <1 a typical off-state supply current 40 c to 85 c operation applications usb keyboard bus-powered hubs usb bus-powered docking stations note book pcs pdas general purpose power distribution applications pc board hot swap 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 ul recognized component
mic2536 2 march 2000 mic2536 micrel pin description pin number pin name pin function 1 ena enable a (input): channel a control input. active high ( 1) or active low ( 2) input. 2 flga flag a: (output): channel a open-drain fault flag output. indicates overcurrent or thermal shutdown conditions. overcurrent conditions must last longer than t d in order to assert flg. 3 flgb flag b (output): channel b open-drain fault flag output. indicates overcur- rent or thermal shutdown conditions. overcurrent conditions must last longer than t d in order to assert flg. 4 enb enable b (input): channel b control input. active high ( 1) or active low ( 2) input. 5 outb output b: channel b switch output. 6 gnd ground 7 in positive switch and logic supply input 8 outa output a: channel a switch output. pin configuration 1 2 3 4 8 7 6 5 outa in gnd outb ena flga flgb enb mic2536-x 8-lead sop (m) 8-lead msop (mm) ordering information part number enable temperature range package MIC2536-1BM active high 40 c to +85 c 8-lead sop mic2536-2bm active low 40 c to +85 c 8-lead sop MIC2536-1BMm active high 40 c to +85 c 8-lead msop mic2536-2bmm active low 40 c to +85 c 8-lead msop
march 2000 3 mic2536 mic2536 micrel electrical characteristics v in = +5v; t a = 25 c, bold values indicate 40 c t a +85 c; unless noted parameter condition min typ max units supply current both switches off, outa b = open, note 4 0.75 5 a both switches on, outa b = open, note 4 60 100 a enable input threshold low-to-high transition, note 4 1.7 2.4 v high-to-low transition, note 4 0.8 1.5 v enable input current v en = 0v to 5.5v 0.01 1 a enable input capacitance note 5 1pf switch resistance single switch, i out = 100ma 400 700 m ? output turn-on delay, t on r l = 50 ? , c l = 1 f 1.5 ms output turn-on rise time, t r r l = 50 ? , c l = 1 f 1.4 ms output turnoff delay, t off r l = 50 ? , c l = 1 f 130 s output turnoff fall time, t f r l = 50 ? , c l = 1 f 115 s output leakage current each output (switch off) 1 10 a current limit threshold ramped load applied to enable output 500 ma short circuit current limit each output (enabled into load), v out = 0v 150 275 400 ma current limit response v out = 0v to i out = i limit (short applied to output), note 5 10 s flag response delay, t d v in = 5v, apply v out = 0v until flg low 5 13 20 ms v in = 3.3v, apply v out = 0v until flg low 13 ms overtemperature shutdown t j increasing, note 5 135 c threshold t j decreasing, note 5 125 c error flag output resistance v in = 5v, i l = 10ma 10 20 ? v in = 3.3v, i l = 10ma 15 30 ? error flag off current v flag = 5v 0.01 1 a 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 mic2536-1. off is 2.4v and on is 0.8v for the mic2536-2. the enable input has approximately 200mv of hysteresis. note 5. guaranteed by design. not production tested. absolute maximum ratings (note 1) supply voltage (v in ) ..................................................... +6v fault flag voltage (v flg ) .............................................. +6v fault flag current (i flg ) ............................................ 25ma output voltage (v out ) .................................................. +6v output current (i out ) ............................... internally limited control input (v en ) ................................... 0.3v to v in +2v storage temperature (t s ) ....................... 65 c to +150 c lead temperature (soldering 5 sec.) ....................... 260 c esd rating, note 3 ...................................................... 1kv operating ratings (note 2) supply voltage (v in ) ................................... +2.7v to +5.5v ambient operating temperature (t a ) ........ 40 c to +85 c thermal resistance sop ( ja ) .......................................................... 160 c/w msop ( ja ) ....................................................... 206 c/w
mic2536 4 march 2000 mic2536 micrel test circuit device under test c l out r l v out functional characteristics test circuit timing diagrams 90% v out 10% 90% 10% t r t f output rise and fall times v en 50% 90% v out 10% t off t on active-high switch delay times (mic2536-1) v en 50% 90% v out 10% t off t on active-low switch delay times (mic2536-2)
march 2000 5 mic2536 mic2536 micrel 0 20 40 60 80 100 23456 supply on current ( a) input voltage (v) supply on current vs. input voltage 25 c 40 c 85 c 0 100 200 300 400 500 600 700 246 on resistance (m ? ) input voltage (v) output on-resistance vs. input voltage 40 c 85 c 25 c 0 1 2 3 4 23456 time (ms) input voltage (v) output rise time vs. input voltage 40 c 25 c 85 c 0 0.5 1.0 1.5 2.0 23456 time ( s) input voltage (v) control voltage vs. input voltage ven falling 40 c 25 c 85 c 108 110 112 114 116 118 120 23456 time (ms) input voltage (v) output fall time vs. input voltage 40 c 25 c 85 c 0 0.5 1.0 1.5 2.0 2.5 23456 threshold voltage (v) input voltage (v) control voltage vs. input voltage ven rising 40 c 25 c 85 c 0 5 10 15 20 23456 time (ms) input voltage (v) flag delay vs. input voltage 40 c 25 c 85 c 0 0.2 0.4 0.6 0.8 1 23456 supply current ( a) input voltage (v) supply off current vs. input voltage 40 c 25 c 85 c 240 250 260 270 280 290 300 23456 current (ma) input voltage (v) current limit threshold vs. input voltage 40 c 25 c 85 c 200 210 220 230 240 250 260 270 280 23456 current (ma) input voltage (v) short circuit current limit vs. input voltage 40 c 25 c 85 c
mic2536 6 march 2000 mic2536 micrel march 2000 5 mic2536 functional characteristics turn-on / turnoff (mic2536-1) i out (100ma/div) v en (10v/div) v out (5v/div) v flg (5v/div) v in = 5v c in = 4.7 f r l = 50 ? c l = 1 f time (1ms/div) turn-on (mic2536-1) i out (100ma/div) v en (10v/div) v out (5v/div) v flg (5v/div) v in = 5v c in = 4.7 f r l = 35 ? c l = 10 f time (1ms/div) turnoff (mic2536-1) i out (100ma/div) v en (10v/div) v out (5v/div) v flg (5v/div) v in = 5v c in = 4.7 f r l = 35 ? c l = 10 f time (1ms/div) turn-on (mic2536-1) i out (100ma/div) v en (10v/div) v out (5v/div) v flg (5v/div) v in = 5v c in = 4.7 f (output current limited) r l = 35 ? c l = 47 f || 10 f time (1ms/div) turnoff (mic2536-1) i out (100ma/div) v en (10v/div) v out (5v/div) v flg (5v/div) v in = 5v c in = 4.7 f r l = 35 ? c l = 47 f || 10 f time (5 s/div) enabled into short circuit (mic2536-1) i out (200ma/div) v en (10v/div) v out (5v/div) v flg (5v/div) v in = 5v c in = 4.7 f out = gnd c l = 0 time (10ms/div) t d
march 2000 7 mic2536 mic2536 micrel ramped into short circuit (mic2536-1) i out (200ma/div) v en (10v/div) v out (5v/div) v flg (5v/div) v in = 5v c in = 4.7 f r l = 0 ? thermal shutdown time (100ms/div) inrush current (mic2536-1) i out (100ma/div) v en (10v/div) v flg (5v/div) v in = 5v c in = 4.7 f r l = 35 ? c l = 410 f c l = 310 f c l = 210 f c l = 110 f c l = 10 time (5 s/div) current-loop response (mic2536-1) i out (1a/div) v out (5v/div) time (5 s/div) v en = 5v v in = 5v c in = 4700 f c l = 47 f output = ground output = open
mic2536 8 march 2000 mic2536 micrel block diagram 1.2v reference thermal shutdown charge pump outb gate control in ena gate control outa flgb charge pump enb osc. flga current limit current limit gnd mic2536 delay delay
march 2000 9 mic2536 mic2536 micrel functional description the mic2536-1 and mic2536-2 are dual high-side switches with active-high and active-low enable inputs, respectively. fault conditions turn off or inhibit turn-on of one or more of the output transistors, depending upon the type of fault, and activate the open-drain error flag transistors making them sink current to ground. input and output in (input) is the power supply connection to the logic circuitry and the drain of each output mosfet. outx (output) is the source of each respective mosfet. in a typical circuit, current flows through the switch from in to outx toward the load. if v out is greater than v in , current will flow from out to in during an on-condition since the mosfet is bidirec- tional when enabled. 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 outx > v in ) when the output is disabled. in this situation, the mic2536 prevents reverse current flow. thermal shutdown each output mosfet has its own thermal sensor. if either or both channels reach 135 c, affected channel(s) will be shut down and flag(s) asserted. 10 c of hysteresis prevents the switches from turning on until the die temperature drops to 125 c. overtemperature detection functions only when at least one switch is enabled. the mic2536 will automatically reset its output when the die temperature cools to approximately 125 c. the mic2536 output and flg signal will continue to cycle on and off until the device is disabled or the fault is removed. depending on pcb layout, package, ambient temperature, etc., it may take several hundred milliseconds from the occurrence of the fault to the output mosfet being shut off. delay to reach thermal shutdown will be shortest with a dead short on the output. current-limit induced thermal shutdown internal circuitry increases the output mosfet on-resis- tance until the series combination of the mosfet on-resis- tance and the load impedance limits output current to ap- proximately 275ma. the resulting increase in power dissipa- tion may cause the shorted channel to go into thermal shutdown. in addition, even though individual channels are thermally isolated, it is possible they may shut down when an adjacent channel is shorted. when this is undesirable, ther- mal shutdown can be avoided by externally responding to the fault and disabling the current-limited channel before the shutdown temperature is reached. the delay between the flag indication of a current-limit fault and thermal shutdown will vary with ambient temperature, board layout, and load impedance, but is typically several seconds. the usb con- troller must therefore recognize a fault and disable the appropriate channel within this time. power dissipation power dissipation depends on several factors such as the load, pcb layout, ambient temperature and package type. equations that can be used to calculate power dissipation and die temperature are found below: calculation of power dissipated by each channel can be accomplished by the following equation: p d = r ds(on) (i out ) 2 total power dissipation of the device will be the summation of p d for both channels. 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 current sensing and limiting the current-limit threshold is preset internally. the preset level prevents damage to the output mosfet and external load but allows a minimum current of 150ma through the output mosfet of each channel. the current-limit circuit senses a portion of the output fet switch current. the current sense resistor shown in the block diagram is virtual and has no voltage drop. the reaction to an overcurrent condition varies with the following three sce- narios: switch enabled into short circuit if a switch is enabled into a heavy load or short circuit, the switch immediately goes into a constant-current mode, re- ducing the output voltage. the flg is asserted indicating an overcurrent condition. short circuit applied to output when a heavy load or short circuit is applied to an enabled switch, a large transient current may flow until the current- limit circuitry responds. once this occurs, the device limits current to less than the maximum short-circuit current-limit specification. current-limit response ramped load the mic2536 current-limit profile exhibits a small foldback effect of approximately 100ma. once this current-limit thresh- old is exceeded the device enters constant-current mode. this constant current is specified as the short-circuit current- limit in the electrical characteristics table. it is important to note that the mic2536 will deliver load current up to the current-limit threshold before entering current-limited opera- tion. fault flag flgx is an open-drain n-channel mosfet output. fault flags are active (low) for current-limit or thermal shutdown. in the case where an overcurrent condition occurs, flg will be asserted only after the flag response delay time, t d has elapsed. this ensures that flg is asserted only upon valid overcurrent conditions and that erroneous error reporting is eliminated. false overcurrent conditions can occur during hot-plug events when a highly capacitive load is connected and causes a high transient inrush current that exceeds the current-limit threshold. the flag response delay time is typi- cally 12ms.
mic2536 10 march 2000 mic2536 micrel applications information supply filtering a 0.1 f to 1 f bypass capacitor from in to gnd, located at the device, is strongly recommended to control supply tran- sients. without a bypass capacitor, an output short may cause sufficient ringing on the input (from supply lead induc- tance) to damage internal control circuitry. input or output transients must not exceed the absolute maximum supply voltage (v in(max) = 6v) even for a short duration. mic2536 ena outa flga flgb gnd enb outb in 0.1f to 1f v in 2.7v to 5.5v figure 1. supply bypassing enable input en must be driven logic high or logic 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. printed circuit board hot-plug the mic2536 is an ideal inrush current-limiter for hot-plug applications. due to the integrated charge pump, the mic2536 presents a high impedance when off and slowly becomes a low impedance as it turns on. this soft-start feature effec- tively isolates power supplies from highly capacitive loads by reducing inrush current. figure 2 shows how the mic2536 may be used in a hot-plug card application. overcurrent transients the mic2536 incorporates an internal circuit designed to prevent flg from being asserted due to transient inrush current. overcurrent events <12ms (typ.) will not assert flg. in case of large capacitive loads (i.e., >430 f), the length of the transient due to inrush current may exceed the delay provided by the integrated filter. since this inrush current exceeds the current-limit delay specification, flg will be asserted during this time. to prevent the logic controller from responding to flg being asserted, an external rc filter, as shown in figure 3, can be used to filter out transient flg assertion. the value of the rc time constant should be selected to match the length of the transient, minus flag t d . mic2536-2 en outa flga flgb gnd outb in 18 27 36 5 enb 4 adaptor card to "hot" receptacle c bulk gnd v cc 0.1 f backend function figure 2. hot-plug card application 10k v+ mic2536 en outa flga flgb gnd enb outb in 18 27 36 45 overcurrent logic controller r c figure 3. transient filter
march 2000 11 mic2536 mic2536 micrel ena outa flga in flgb gnd enb outb mic2536-2 3.3v usb controller 0.1f v bus d+ d gnd data (two pair) v bus d+ d gnd usb port 2 usb port 1 mic5207-3.3 63f 63f ferrite beads 4.50v to 5.25v upstream v bus 100ma max. v bus d+ d gnd data 4.7f 1f to usb controller 1.5k on/off overcurrent overcurrent on/off vin 10k in out gnd .01f .01f 10k figure 4. usb two-port bus-powered hub universal serial bus (usb) power distribution applications the mic2536 is ideally suited for usb (universal serial bus) power distribution applications. for bus-powered hubs, usb requires that each downstream port be switched on or off under control by the host. up to four downstream ports each capable of supplying 100ma at 4.4v minimum are allowed. in additon, to reduce voltage droop on the upstream bus the hub must consume only 100ma max at start-up until it enumer- ates with the host prior to requesting more power. the same requirements apply for bus-powered peripherals that have no downstream ports. figure 4 shows a two-port bus-powered hub. bus-powered hub port switching the usb specification requires that bus-powered hubs imple- ment port switching on either a ganged or individual basis. the specific implementation must be reported via the hub descriptor status register. individual port switching has advantages in that a fault on one port will not prevent the other ports from operating correctly. in addition, a soft-start circuit must be included in order to reduce inrush currents when the switch is enabled. to meet this requirement, the mic2536 has been designed to slowly ramp its output. suspend current universal serial bus specification places a maximum sus- pend current requirement of 500 a on devices. for hubs, universal serial bus specification revision 1.1 clarifies this issue. revision 1.1, section 7.2.3, stipulates that the maxi- mum suspend current for a configured hub is 2.5ma. this number is derived by allocating 500 a for up to four down- stream ports plus 500 a for the hub s internal functions. a nonconfigured hub is considered a low-power device and may not consume more than 500 a. in a nonconfigured state all downstream devices will be switched off. in most cases, a nonconfigured hub is not a practical state for the system. therefore, the 2.5ma specification is the applicable target specification for the suspend state. in a bus-powered hub with less than 4 ports, the hub may use the additional current for internal functions. the 500 a worst case suspend current must be further divided among the data port termination resistors and internal functions. the termination resistors will consume 3.6v (16.5k ? 5%) = 230 a. this leaves only 270 a for internal functions. assuming 100 a as the maximum usb controller suspend current, 170 a remains for the rest of the system. the mic2536 will consume 100 a maximum, leav- ing a margin of 70 a. usb voltage regulation usb specifications require a minimum downstream voltage supply of 4.40v from a bus-powered hub port (see applica- tion note 17 for details). the usb specification allows for a 100mv drop across the hub, leaving 250mv for pcb, up- stream cable, and connector resistance. therefore, the on- resistance of the switch for each port, not including pcb resistance, must be <100mv 100ma = 1 ? . the mic2536 has a maximum on-resistance of 700m ? , which easily satis- fies this requirement. overcurrent indication the usb specification does not require bus-powered hubs to report overcurrent conditions to the host, since the hub is already current-limited at the upstream port. however, if it is desired to report overcurrent, the hub descriptor status register must be programmed to indicate this. the mic2536 provides a flag output for this application.
mic2536 12 march 2000 mic2536 micrel package information 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-lead sop (m) 0.008 (0.20) 0.004 (0.10) 0.039 (0.99) 0.035 (0.89) 0.021 (0.53) 0.012 (0.03) r 0.0256 (0.65) typ 0.012 (0.30) r 5 max 0 min 0.122 (3.10) 0.112 (2.84) 0.120 (3.05) 0.116 (2.95) 0.012 (0.03) 0.007 (0.18) 0.005 (0.13) 0.043 (1.09) 0.038 (0.97) 0.036 (0.90) 0.032 (0.81) dimensions: inch (mm) 0.199 (5.05) 0.187 (4.74) 8-lead msop (mm)
march 2000 13 mic2536 mic2536 micrel 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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