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sc2041 ? 2000 semtech corp. hotswitch? usb power distribution switch with shutdown july 18, 2000 652 mitchell road newbury park ca 91320 1 description usb power distribution switches are high-side n-channel mosfet switches with built-in overcurrent protection and low on-state resistance. the sc2041 switch is designed to meet the usb requirements for power switching and maintenance-free fault protection for self-powered & bus-powered hub applications. the sc2041 features low on-state resistance to meet the usb requirement for voltage drop and regulation. the switch is controlled by a shutdown input that is compatible with 3v and 5v logic. the device is active when the shutdown input is low. see sc2051 for an active high version. the device provides short circuit current limiting at a value of less than 1.0a, well below the usb limit of 5a. during an overcurrent condition the device provides a fault notification to signal the usb controller. an integrated thermal protection circuit automatically shuts the switch off when the junction temperature reaches its thermal limit. the switch remains off until the junction temperature drops approximately 20c. the switch will continue to cycle on and off until the fault is removed. inrush current limiting prevents voltage drop on an upstream port when the switch is enabled. an undervoltage lockout circuit guarantees the switch is initially off during start-up. tel:805-498-2111 fax:805-498-3804 web:http:// www.semtech.com ordering information note: (1) only available in tape and reel packaging. a reel contains 2500 devices. device (1) package sc2041is.tr so-8 features ? = designed to meet usb specification revisions 1.1 and 2.0 power management requirements ? = 500ma continuous load current ? = high-side mosfet switch with low r ds(on) ? = short-circuit current protection ? = internal thermal shutdown ? = undervoltage lockout ? = open drain fault output ? = soft start circuit with slow turn-on time ? = wide supply voltage range: 2.8v to 5.5v ? = 2.5kv esd rating (human body model) ? = full industrial temperature range applications ? = universal serial bus (usb) power management ? = self-powered or bus-powered usb hubs ? = root hubs in desktop pcs & servers ? = notebook pcs ? = peripherals typical application circuit vbus in flag output to usb controller vbus out shutdown signal from usb controller u1 sc2041 1 2 3 4 5 6 7 8 gnd in in shdn flg out out out c2 0.1uf c3 22uf r1 c1 0.1uf
sc2041 ? 2000 semtech corp. hotswitch? usb power distribution switch with shutdown july 18, 2000 652 mitchell road newbury park ca 91320 2 absolute maximum ratings parameter symbol maximum units input voltage range v in -0.3 to +7 v output voltage range v out -0.3 to +7 v shutdown input v en -0.3 to +7 v flag output v flg -0.3 to (v in + 0.3) v continuous output current i o internally limited ma thermal impedance junction to ambient ja 130 c/w thermal impedance junction to case jc 47 c/w operating ambient temperature range t a -40 to +85 c operating junction temperature range t j -40 to +125 c storage temperature range t stg -65 to +150 c lead temperature (soldering, 10 seconds) t l 300 c esd rating (human body model) esd 2.5 kv electrical characteristics unless specified: t a = 25c, v in = 5v, v shdn = gnd, i out = 500ma. values in bold apply over the full operating temperature range. parameter symbol conditions min typ max units in supply voltage range v in 2.8 5.5 v supply current i q v in = 3.3v 85 130 a 200 v in = 5.0v 100 130 a 200 v shdn = v in = 5.5v (off) 0.1 1 a power switch on resistance r on v in = 3.3v 85 105 m ? 150 v in = 5.0v 80 100 135 out output leakage current i l(off) v in = v shdn = 5.5v, v out = gnd 0.01 1 a output turn on delay t d(on) r out = 10 ? , c out = 1f 0.9 ms output turn on rise time t r r out = 10 ? , c out = 1f 1.7 ms output turn off delay t d(off) r out = 10 ? , c out = 1f 20 s output turn off fall time t f r out = 10 ? , c out = 1f 25 s
sc2041 ? 2000 semtech corp. hotswitch? usb power distribution switch with shutdown july 18, 2000 652 mitchell road newbury park ca 91320 3 electrical characteristics (cont.) unless specified: t a = 25c, v in = 5v, v shdn = gnd, i out = 500ma. values in bold apply over the full operating temperature range. parameter symbol conditions min typ max units current limit short circuit current limit i cl v out = gnd 0.60 0.85 1.10 a current limit trip threshold i th(cl) 1.5 a shdn high level input voltage v ih 2.8v v in 5.50v 2.4 v low level input voltage v il 2.8v v in 5.50v 0.8 v input current i shdn v shdn = v in = 5.5v, v out = open 1 a v shdn = gnd, i out = 0ma, v out = open 1 undervoltage lockout uvlo threshold v uvlo v in rising 2.7 v v in falling 2.4 v flg output resistance r flg i flg = 10ma, v o = gnd, switch on 50 ? leakage current (off) i flg v flg = 5.0v, switch off 1 a over temperature protection high trip level t hi 150 c hysteresis t hyst 20 c timing diagram: output turn on/off delay times and rise/fall times
sc2041 ? 2000 semtech corp. hotswitch? usb power distribution switch with shutdown july 18, 2000 652 mitchell road newbury park ca 91320 4 pin description pin # pin name pin function 1 gnd ground. 2, 3 in input voltage: drain of n-channel power mosfet. connect to supply voltage. 4 shdn shutdown input: ttl compatible. n-channel power mosfet is turned on when this pin is pulled low. 5 flg error flag output: flg is asserted active low during a fault condition (overcurrent, input undervoltage or thermal shutdown). 6, 7,8 out power switch output: source of n-channel power mosfet. connect to load. block diagram pin configuration top view (8-pin soic)
sc2041 ? 2000 semtech corp. hotswitch? usb power distribution switch with shutdown july 18, 2000 652 mitchell road newbury park ca 91320 5 typical characteristics 0 20 40 60 80 100 120 -50 -25 0 25 50 75 100 125 t j (c) i q(on) (a) i out = 500ma v shdn = gnd v in = 3.0v v in = 3.3v v in = 5.0v on-state quiescent current vs. junction temperature vs. input voltage 0 20 40 60 80 100 120 2.5 3.0 3.5 4.0 4.5 5.0 5.5 v in (v) i q(on) (a) t j = 25c i out = 500ma v shdn = gnd on-state quiescent current vs. input voltage 55 65 75 85 95 105 115 125 135 -50 -25 0 25 50 75 100 125 t j (c) r on (m ? ? ? ? ) v shdn = gnd i out = 500ma top to bottom: v in = 3.0v v in = 3.3v v in = 5.0v power switch on resistance vs. junction temperature vs. input voltage 0 50 100 150 200 250 300 2.5 3.0 3.5 4.0 4.5 5.0 5.5 v in (v) i q(off) (na) t a = 25c t a = -40c t a = 125c v shdn = v in 0.0 0.5 1.0 1.5 2.0 2.5 2.5 3.0 3.5 4.0 4.5 5.0 5.5 v in (v) t r (ms) c out = 1f r out = 6.6 ? (v in = 2.8v and 3.3v) r out = 10 ? (v in = 5v and 5.5v) t j = 125c t j = 25c t j = -40c output turn-on rise time vs. input voltage vs junction temperature 55 65 75 85 95 105 115 125 135 2.5 3.0 3.5 4.0 4.5 5.0 5.5 v in (v) r on (m ? ? ? ? ) t j = 125c t j = 25c t j = -40c v shdn = gnd i out = 500ma off-state quiescent current vs. input voltage vs. junction temperature power switch on resistance vs. input voltage vs. junction temperature
sc2041 ? 2000 semtech corp. hotswitch? usb power distribution switch with shutdown july 18, 2000 652 mitchell road newbury park ca 91320 6 typical characteristics (cont.) 0.60 0.65 0.70 0.75 0.80 0.85 0.90 0.95 2.5 3.0 3.5 4.0 4.5 5.0 5.5 v in (v) i cl (a) top to bottom: t j = -40c t j = 25c t j = 125c v shdn = v in v out = gnd short circuit current limit vs. input voltage vs. junction temperature 0.60 0.65 0.70 0.75 0.80 0.85 0.90 -50 -25 0 25 50 75 100 125 t j (c) i cl (a) v shdn = v in v out = gnd v in = 5.0v v in = 3.3v v in = 3.0v short circuit current limit vs. junction temperature vs. input voltage 0.00 0.25 0.50 0.75 1.00 1.25 1.50 1.75 2.00 2.5 3.0 3.5 4.0 4.5 5.0 5.5 v in (v) v th(shdn) (v) top to bottom: t j = -40c t j = 25c t j = 125c shutdown threshold vs. input voltage vs. junction temperature 1.0 1.1 1.2 1.3 1.4 1.5 1.6 -50 -25 0 25 50 75 100 125 t j (c) i th(cl) (a) v in = 5.0v v in = 3.3v v in = 3.0v v shdn = v in v out = gnd current limit trip threshold vs. junction temperature vs. input voltage 2.40 2.45 2.50 2.55 2.60 2.65 2.70 2.75 2.80 -50 -25 0 25 50 75 100 125 t j (c) v uvlo (v) v in rising v in falling undervoltage lockout vs. junction temperature 0 5 10 15 20 25 30 35 40 2.53.03.54.04.55.05.5 v in (v) r flg ( ? ? ? ? ) top to bottom: t j = 125c t j = 25c t j = -40c i flg = 10ma v out = gnd switch on error flag output resistance vs. input voltage vs. junction temperature
sc2041 ? 2000 semtech corp. hotswitch? usb power distribution switch with shutdown july 18, 2000 652 mitchell road newbury park ca 91320 7 figure 1: output turn on delay and rise time with 0.1f output capacitor and no load typical characteristics (cont.) figure 2: output turn on delay and rise time with 1f output capacitor and 10 ? ? ? ? load top trace: v shdn , 5v/div. bottom trace: v out , 2v/div. timebase: 1ms/div. v in = 5v, r out = 10 ? , c out = 1f top trace: v shdn , 5v/div. bottom trace: v out , 2v/div. timebase: 1ms/div. v in = 5v, r out = open, c out = 0.1f figure 4: current limit and trip threshold with ramped load on enabled device top trace: v out , 5v/div. bottom trace: i out , 0.5a/div. timebase: 100ms/div. v in = 5v, r out ramping from open to 1.1 ? , c out = 22f top trace: v out , 5v/div. bottom trace: i out , 0.5a/div. timebase: 100ms/div. v in = 5v, r out ramping from open to 1.1 ? , c out = 22f figure 3: output turn off delay and fall time with 1f output capacitor and 10 ? ? ? ? load
sc2041 ? 2000 semtech corp. hotswitch? usb power distribution switch with shutdown july 18, 2000 652 mitchell road newbury park ca 91320 8 typical characteristics (cont.) figure 6: short circuit current, device enabled into short top trace: v shdn , 5v/div. bottom trace: i out , 0.2a/div. timebase: 1ms/div. v in = 5v, r out = 0 ? figure 7: short circuit current, short applied to enabled device top trace: v flg , 5v/div. bottom trace: i out , 5a/div. timebase: 250s/div. v in = 5v, r out = 0 ? , c out = 22f note initial output current spike from output capacitor discharge figure 8: current limit, 1.1 ? ? ? ? load applied to enabled device top trace: v flg , 5v/div. bottom trace: i out , 1a/div. timebase: 250s/div. v in = 5v, r out = 1.1 ? , c out = 1f figure 5: current limit and trip threshold with ramped load on enabled device top trace: v flg , 5v/div. bottom trace: i out , 0.5a/div. timebase: 100ms/div. v in = 5v, r out ramping from open to 1.1 ? , c out = 22f
sc2041 ? 2000 semtech corp. hotswitch? usb power distribution switch with shutdown july 18, 2000 652 mitchell road newbury park ca 91320 9 typical characteristics (cont.) figure 10: inrush current, device enabled into 470f and 10 ? ? ? ? top trace: v shdn , 5v/div. bottom trace: i out , 0.2a/div. timebase: 2.5ms/div. v in = 5v, r out = 10 ? , c out = 470f applications information theory of operation the sc2041 is a current limited 80m ? power switch with error reporting and enable features. the power switch is an n-channel mosfet with its gate driven by an internal charge pump. the switch has been de- signed to turn on slowly (1.7ms typical) to minimize inrush currents at turn-on. the shutdown pin (shdn) is compatible with 3v or 5v logic, and when pulled high, shuts off the power switch, causing the device to enter a very low power shutdown mode, where it will draw less than 1a from the supply. while enabled, the sc2041 draws only 100a from the supply. the power switch has current limit detection circuitry which will limit the current through the switch to 0.85a (typical) and reduce the output voltage accordingly. when current limit is entered, the open drain flag pin (flg) is asserted low, indicating a fault condition. if an overcurrent or short condition is continuous, the power dissipation in the switch will cause the junction temper- ature to rise, triggering the thermal protection circuitry to shut the switch down (at t j = 150c typical). this will shut off the output current altogether, and also cause the flag pin to be asserted low. once the junction temperature has dropped by 20c (typical), the device will start up once more in a controlled manner. the sc2041 will operate from supply voltages as low as 2.8v, and internal undervoltage lockout circuitry ensures that the power switch will be turned off at power-up, even if the device is enabled. once the uvlo threshold voltage (2.7v typical) is reached, the switch will turn on (if enabled) and slowly ramp up the output. the sc2041 has been designed for use in usb appli- cations such as: 1) hosts or self-powered hubs that need to current limit downstream ports and report overcurrent conditions; 2) bus-powered hubs that need to be able to switch power to downstream ports, limit inrush currents at power-up (to less than a 44 ? resistor in parallel with a 10f capacitor) and power-up and draw less than 100ma; 3) bus-powered functions that need to limit inrush currents at power-up (to less than a 44 ? resistor in parallel with a 10f capacitor) and power-up and draw less than 100ma. figure 9: inrush current, device enabled into 100f and 10 ? ? ? ? top trace: v shdn , 5v/div. bottom trace: i out , 0.2a/div. timebase: 2.5ms/div. v in = 5v, r out = 10 ? , c out = 100f
sc2041 ? 2000 semtech corp. hotswitch? usb power distribution switch with shutdown july 18, 2000 652 mitchell road newbury park ca 91320 10 overcurrent circuitry reacts. once the current limit cir- cuitry trips, the current is limited to 0.85a and flg is asserted low. refer to figure 7 on page 8. 3) the load gradually increases beyond 500ma. in this case, the current will be allowed to rise until it reaches the current limit trip threshold, at which point the current will drop back to 0.85a and flg will assert low. refer to figures 4 and 5 on page 7 and 8. thermal sensing an internal thermal shutdown circuit turns off the power switch when the die temperature exceeds 150c (typical). the flg pin asserts low signaling a fault condition. built-in hysteresis prevents the switch from turning back on until the die temperature has cooled approximately 20c. the switch will continue to cycle on and off until the fault condition is removed. the thermal sense circuit functions only when the switch is enabled. undervoltage lockout an undervoltage lockout circuit monitors the input volt- age and prevents the power switch from turning on until the input voltage (in) exceeds 2.7v (typical). if the input voltage falls and drops below 2.4v (typical), the under- voltage circuitry turns off the power switch and the flg pin asserts low. the undervoltage lockout functions only when the switch is enabled. thermal considerations since the on-resistance of the power switch is so low, the sc2041 can pass large currents without requiring a large package to dissipate the heat. the worst-case power dissipation (under normal operating conditions) is given by: so for i out = 500ma and r on(max) = 150m ? (at v in = 3.3v), the maximum power dissipation is: the junction temperature can be calculated using the following equation: inserting t a = 85c, ja = 130c/w (package thermal impedance for minimum line widths and no internal component selection - general a 0.1f or greater ceramic bypass capacitor is recom- mended at the device input. this should be placed close to the input pin (in) and routed directly to ground. a low esr electrolytic capacitor is recommended at the output, higher values should be used for heavy loads to reduce ringing at the output (and hence input). bypass the output with a 0.1f to 1f ceramic capacitor to improve immunity to short circuit transients. shutdown the shutdown pin (shdn) input is a 3v or 5v compatible enable/disable. pulling this pin high shuts down the power switch and the sc2041 will draw < 1a from the supply. pulling this pin low will enable the device. error flag the error flag (flg) output is an open drain n-channel mosfet. its output is pulled low during overcurrent, input undervoltage and thermal shutdown conditions. connection of high capacitance loads to the output can cause momentary overcurrent conditions due to inrush current and trigger false error flag assertion. this can be reduced by using low esr output capacitors to provide a low impedance source for hot-plug events. the addition of an rc filter between flg and the usb controller can resolve this easily. this pin also requires a pull-up resistor for a high signal when not asserted. overcurrent there are three overcurrent situations to be consid- ered: 1) the output is already short before the device is enabled or power is applied. in this case, the sc2041 immediately detects the short, and the output current will slowly ramp up to the current limit value, and flg will assert low. refer to figure 6 on page 8. 2) a short occurs while the device is enabled. in this case, very high current may flow initially while the vbus in flag output to usb controller vbus out shutdown signal from usb controller u1 sc2041 1 2 3 4 5 6 7 8 gnd in in shdn flg out out out c2 0.1uf c3 22uf r1 c1 0.1uf pir dmax out onmax () () () =? 2 pmw dmax () (.) . . =?= 0 5 0 150 37 5 2 tt p jajadmax =+ ? () applications information (cont.)
sc2041 ? 2000 semtech corp. hotswitch? usb power distribution switch with shutdown july 18, 2000 652 mitchell road newbury park ca 91320 11 power planes) and p d(max) = 37.5mw, we calculate the worst-case t j to be: thus it can be seen that this device does not require any additional copper area for heatsinking under normal operating conditions. sustained overcurrents or short circuits will rapidly heat t j > 150c, thus activating the thermal shutdown circuitry. tc j =+ ? = 85 130 0 0375 90 . u2 sc5205-3.3 1 2 3 4 5 vin gnd en byp vo u3 sc2041 1 2 3 4 5 6 7 8 gnd in in shdn flg out out out downstream port vbus d+ d- gnd upstream port d+ d- vbus gnd c2 10nf c3 4.7uf c1 4.7uf ferrite bead ferrite bead c4 0.1uf c5 33uf usb controller d0d+ d0d- vcc en oc d1d+ d1d- r1 100k 5v power supply +5v gnd u4 srda05-4 i/o1 i/o2 i/o3 i/o4 ref2 ref2 ref1 ref1 self-powered hub, individual port power management: a self-powered hub must supply a continuous 500ma of current to each downstream port. since an internal power supply is used to supply the power, self-powered hubs are required to implement overcurrent protection for safety. the self-powered hub must also have a method to detect and report fault conditions to the usb controller. the circuit below utilizes the sc2041 to provide individual port overcurrent protection & power switching for maximum port protection. under fault conditions, the sc2041 provides the short-circuit current limiting function and has a fault flag logic output layout considerations the ceramic bypass capacitors for in and out should be connected as close to the relevant device pins as possible. the bulk output capacitors required by the usb specification should be placed close to the usb connector to provide a low impedance source for hot plug purposes. ferrite beads should be placed on the v bus and ground pins of the downstream connectors to reduce the droop on adjacent ports during hot plug events. typical applications circuits for notifying the hub controller. the usb hub can use the sc2041 to remove power from the faulty port, allowing the other ports to operate normally. since usb is a hot insertion and removal system, usb ports are subject to electrostatic discharge (esd). the srda05-4 provides esd protection on the downstream data and power lines. each device will protect two usb ports. with proper layout the port is hardened to greater than 15kv, meeting the requirements of iec 1000-4-2. the sc5205 ldo regulator is used to power the hub controller from the hub?s 5v power supply. applications information (cont.) notes: (1) one port only shown for simplicity. (2) 33f output capacitor assumes four downstream ports for this hub, therefore meeting the usb specification requirement of 120f minimum capacitance per hub. (3) the srda05-4 shown would also protect lines d2d+ and d2d-.
sc2041 ? 2000 semtech corp. hotswitch? usb power distribution switch with shutdown july 18, 2000 652 mitchell road newbury park ca 91320 12 typical applications circuits (cont.) bus-powered hub, ganged-port power management: a bus-powered hub distributes power and data from an input port to downstream ports. it must supply a contin- uous 100ma of current to each downstream port. a bus-powered hub must be able to switch power to downstream ports to prevent illegal device hook-up. inrush current limiting is also required to prevent power supply drooping. the circuit below utilizes the sc2041 to provide ganged port power switching, inrush current limiting and overcurrent protection for maximum port protection. in a ganged switch configuration, all ports are switched simultaneously. under fault conditions, the usb controller will remove power to all of the ganged ports. for individual port management, additional sc2041s may be used. since usb is a hot insertion and removal system, usb ports are subject to electrostatic discharge (esd). the srda05-4 provides esd protection on the downstream data and power lines. each device will protect two usb ports. with proper layout the port is hardened to greater than 15kv, meeting the requirements of iec 1000-4-2. on the upstream port, the sr05 provides esd protec- tion to the above levels for one line pair. the sc5205 ldo regulator is used to power the hub controller from the upstream bus. ferrite bead ferrite bead ferrite bead ferrite bead ferrite bead ferrite bead ferrite bead usb controller d0d+ d0d- vcc en oc d1d+ d1d- oc oc oc d2d+ d2d- d3d+ d3d- d4d+ d4d- downstream port vbus d+ d- gnd downstream port vbus d+ d- gnd downstream port vbus d+ d- gnd c6 33uf c7 33uf c8 33uf u1 sr05 1 2 3 4 1 23 4 u2 sc5205-3.3 1 2 3 4 5 vin gnd en byp vo u3 sc2041 1 2 3 4 5 6 7 8 gnd in in shdn flg out out out upstream port d+ d- vbus gnd c2 10nf c3 4.7uf downstream port vbus d+ d- gnd c1 4.7uf c4 0.1uf r1 100k u4 srda05-4 i/o1 i/o2 i/o3 i/o4 ref2 ref2 ref1 ref1 u5 srda05-4 i/o1 i/o2 i/o3 i/o4 ref2 ref2 ref1 ref1 ferrite bead c5 33uf note: (1) 33f output capacitor per port meets the usb specification minimum capacitance requirement of 120f per hub.
sc2041 ? 2000 semtech corp. hotswitch? usb power distribution switch with shutdown july 18, 2000 652 mitchell road newbury park ca 91320 13 typical applications circuits (cont.) high-power or low-power bus-powered function: both low-power and high-power bus-powered functions must draw less than 100ma at startup. at this time, they must also present a load of less than the parallel combination of a 44 ? resistor and a 10f capacitor. after startup, high powered functions may then draw up to 500ma. the circuit below utilizes the sc2041 to provide inrush current limiting and power switching for the internal function. since usb is a hot insertion and removal system, usb ports are subject to electrostatic discharge (esd). the sr05 provides esd protection on the upstream data and power lines. with proper layout the port is hard- ened to greater than 15kv, meeting the requirements of iec 1000-4-2. the sc5205 ldo regulator is used to power the hub controller from the upstream bus. note: (1) 33f output capacitor per port meets the usb specification minimum capacitance of 120f per hub. c1 10uf c4 0.1uf upstream port d+ d- vbus gnd c3 4.7uf u2 sc5205-3.3 1 2 3 4 5 vin gnd en byp vo c5 10uf r1 100k c2 10nf u1 sr05 1 2 3 4 1 23 4 u3 sc2041 1 2 3 4 5 6 7 8 gnd in in shdn flg out out out usb controller d0d+ d0d- vcc en oc internal function vcc gnd
sc2041 ? 2000 semtech corp. hotswitch? usb power distribution switch with shutdown july 18, 2000 652 mitchell road newbury park ca 91320 14 outline drawing - so-8 jedec ref: ms-012aa land pattern - so-8 ecn00-1199

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