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RT9721A/b 1 ds9721a/b-02 april 2011 www.richtek.com ordering information note : richtek products are : ` rohs compliant and compatible with the current require- ments of ipc/jedec j-std-020. ` suitable for use in snpb or pb-free soldering processes. marking information for marking information, contact our sales representative directly or through a richtek distributor located in your area. 80m , 500ma high-side power switches with flag general description the RT9721A/b are low voltage, single n-mosfet high- side power switches, optimized for self-powered and bus- powered universal serial bus (usb) applications. the RT9721A/b series provides a charge pump circuitry to drive the internal mosfet switch; the switch's low r ds(on) , 80m , meets usb voltage drop requirements; and a flag output is available to indicate fault conditions to the local usb controller. additional features include soft-start to limit inrush current during plug-in, thermal shutdown to prevent catastrophic switch failure from high-current loads, under-voltage lockout (uvlo) to ensure that the device remains off unless there is a valid input voltage present. the maximum current is limited to typically 750ma in dual ports in accordance with the usb power requirements, lower quiescent current as 50ua making this device ideal for portable battery-operated equipment. the RT9721A is designed without output auto-discharge function and rt9721b is designed with output auto- discharge function. the RT9721A/b are available in sot-23-5 package requiring minimum board space and smallest components. features z z z z z compliant to usb specifications z z z z z built-in n-mosfet ` ` ` ` ` typical r ds(on) : 80m z z z z z output can be forced to higher than input (off- state) z z z z z low supply current : ` ` ` ` ` 50 a typical at switch on state ` ` ` ` ` 0.1 a typical at switch off state z z z z z guaranteed 500ma continuous load current z z z z z wide input voltage ranges : 2.5v to 5.5v z z z z z open-drain fault flag output z z z z z hot plug-in application (soft-start) z z z z z 2.15v typical under-voltage lockout (uvlo) z z z z z current limiting protection z z z z z thermal shutdown protection z z z z z reverse current flow blocking (no body diode) z z z z z ul approved ? ? ? ? ? e219878 z z z z z rohs compliant and halogen free applications z usb bus/self powered hubs z usb peripherals z notebook, motherboard pcs pin configurations (top view) sot-23-5 vin gnd vout en flg 4 23 5 rt9721 package type b : sot-23-5 lead plating system g : green (halogen free and pb free) output discharge function a : without auto-discharge function b : with auto-discharge function
RT9721A/b 2 ds9721a/b-02 april 2011 www.richtek.com typical application circuit functional pin description pin no. pin name pin function 1 vin switch input voltage. 2 gnd ground. 3 en chip enable (active high). 4 flg open-drain fault flag output. 5 vout switch output voltage. function block diagram vin vout gnd RT9721A/b + over -current v bus d+ d- gnd usb controller 1f 150f 10f supply voltage 5v ferrite beads data flg en c in c out chip enable pull-up resistor (10k to 100k) 1 2 3 4 5 gate control output voltage detection delay oscillator uvlo charge pump bias thermal protection current limiting vout vin gnd en auto discharge flg rt9721b only
RT9721A/b 3 ds9721a/b-02 april 2011 www.richtek.com absolute maximum ratings (note 1) z supply input voltage, v in ------------------------------------------------------------------------------------------------ 6v z en input voltage ----------------------------------------------------------------------------------------------------------- ? 0.3v to 6v z flag voltage ---------------------------------------------------------------------------------------------------------------- 6v z power dissipation, p d @ t a = 25 c sot-23-5 -------------------------------------------------------------------------------------------------------------------- 0.4w z package thermal resistance (note 2) sot-23-5, ja --------------------------------------------------------------------------------------------------------------- 250 c/w z lead temperature (soldering, 10 sec.) ------------------------------------------------------------------------------- 260 c z junction temperature ----------------------------------------------------------------------------------------------------- 150 c z storage temperature range -------------------------------------------------------------------------------------------- ? 65 c to 150 c z esd susceptibility (note 3) hbm -------------------------------------------------------------------------------------------------------------------------- 4k v mm ---------------------------------------------------------------------------------------------------------------------------- 4 00v recommended operating conditions (note 4) z supply input voltage range, v in --------------------------------------------------------------------------------------- 2.5v to 5.5v z en input voltage range -------------------------------------------------------------------------------------------------- 0v to 5 .5v z junction temperature range -------------------------------------------------------------------------------------------- ? 40 c to 125 c z ambient temperature range -------------------------------------------------------------------------------------------- ? 40 c to 85 c electrical characteristics parameter symbol test conditions min typ max unit switch on resistance r ds(on) v in = 5v, i out = 100ma -- 80 100 m i sw_on switch on, v out = open -- 50 70 supply current i sw_off switch off, v out = open -- 0.1 1 a logic-low voltage v il v in = 2.5v to 5.5v, switch off -- -- 0.8 v en threshold logic-high voltage v ih v in = 2.5v to 5.5v, switch on 2 -- -- v en input current i en v en = 5v -- 0.01 0.1 a output leakage current i leakage v en = 0v, r load = 0 -- 0.5 1 a output turn-on rise time t on _ris e 10% to 90% of v out rising -- 200 -- s current limit detect threshold i lim_thres hold i ou t rising -- -- 1 a current limit i lim v out = 4v 500 -- 900 ma flg output resistance r flg i sin k = 1ma -- 10 -- flg off current i flg_off v flg = 5v -- 0.01 1 a flg delay time (note 5) t d from fault condition to flg assertion 5 12 20 ms shutdown auto-discharge resistance r discharge v en = 0v -- 100 150 (v in = 5v, c in = 1 f, c out = 10 f, t a = 25 c, unless otherwise specified) to be continued
RT9721A/b 4 ds9721a/b-02 april 2011 www.richtek.com note 1. stresses listed as the above ? absolute maximum ratings ? may cause permanent damage to the device. these are for stress ratings. functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. exposure to absolute maximum rating conditions for extended periods may remain possibility to affect device reliability. note 2. ja is measured in the natural convection at t a = 25 c on a low effective single layer thermal conductivity test board of jedec 51-3 thermal measurement standard. note 3. devices are esd sensitive. handling precaution is recommended. note 4. the device is not guaranteed to function outside its operating conditions. note 5. the flag delay time is input voltage dependent, see ? typical operating characteristics ? graph for further details. parameter symbol test conditions min typ max unit under-voltage lockout v uvlo v in increasing 1.9 2.15 2.4 v under-voltage hysteresis v uvlo v in decreasing -- 0.1 -- v thermal shutdown protec ti on t sd -- 150 -- c thermal shutdown hysteresis t sd -- 25 -- c
RT9721A/b 5 ds9721a/b-02 april 2011 www.richtek.com typical operating characteristics on resistance vs. input voltage 80 85 90 95 100 105 110 2.5 3 3.5 4 4.5 5 5.5 input voltage (v) on resistance (m ? ) i out = 100ma switch off supply current vs. input voltage 0.00 0.05 0.10 0.15 0.20 0.25 0.30 2.5 3 3.5 4 4.5 5 5.5 input voltage (v) switch off supply current (ua) no load on resistance vs. temperature 50 70 90 110 130 150 -50 -25 0 25 50 75 100 125 temperature on resistance (m ? ) v in = 5v, i out = 100ma ( c) switch on supply current vs. temperature 25.0 27.5 30.0 32.5 35.0 37.5 40.0 42.5 45.0 -50 -25 0 25 50 75 100 125 tmeperature switch on supply current (ua) v in = 5v, no load ( c) switch off supply current vs. temperature 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 -50 -25 0 25 50 75 100 125 temperature switch off supply current (ua) v in = 5v, no load ( c) switch on supply current v s. input voltage 25 27.5 30 32.5 35 37.5 40 42.5 45 2.5 3 3.5 4 4.5 5 5.5 input voltage (v) switch on supply current (ua) 1 no load
RT9721A/b 6 ds9721a/b-02 april 2011 www.richtek.com output turn-on rise time vs. input voltage 80 100 120 140 160 180 200 220 2.5 3 3.5 4 4.5 5 5.5 input voltage (v) output turn-on rise time (us) 1 current limit detect threshold vs. temperature 500 600 700 800 900 1000 -50-25 0 25 50 75100125 temperature current limit detect threshold (ma) v in = 5v ( c) current limit detect threshold vs. input voltage 500 600 700 800 900 1000 2.5 3 3.5 4 4.5 5 5.5 input voltage (v) current limit detect threshold (ma) no load output voltage vs. output current 0 1 2 3 4 5 6 0 100 200 300 400 500 600 700 800 900 100 0 output current (ma) output volttage (v) v in = 5v 1000 output turn-on rise time vs. temperature 150 170 190 210 230 250 -50 -25 0 25 50 75 100 125 temperature output turn-on rise time (us) ( c) v in = 5v, no load uvlo threshold vs. temperature 1.5 1.7 1.9 2.1 2.3 2.5 -50 -25 0 25 50 75 100 125 temperature uvlo threshold (v) rising falling ( c)
RT9721A/b 7 ds9721a/b-02 april 2011 www.richtek.com flag delay time vs. input voltage 2 4 6 8 10 12 14 2.5 3 3.5 4 4.5 5 5.5 input voltage (v) flag delay time (ms) r load = 0 flag delay time vs. temperature 10.0 10.5 11.0 11.5 12.0 12.5 13.0 13.5 14.0 -50 -25 0 25 50 75 100 125 temperature flag delay time (ms) v in = 5v, r load = 0 ( c) current limit vs. temperature 500 550 600 650 700 750 800 850 900 -50 -25 0 25 50 75 100 125 temperature current limit (ma) v in = 5v, v out = 4v ( c) current limit vs. input voltage 500 550 600 650 700 750 800 850 900 2.5 3 3.5 4 4.5 5 5.5 input voltage (v) current limit (ma) v in ? v out = 1v en threshold volatge vs. input voltage 0.8 1.0 1.2 1.4 1.6 1.8 2.0 2.5 3 3.5 4 4.5 5 5.5 input voltage (v) en threshold voltage (v) rising falling power on from v in time (2ms/div) v out (2v/div) v in (2v/div) r load = 200
RT9721A/b 8 ds9721a/b-02 april 2011 www.richtek.com thermal shutdown response time (400ms/div) v out (5v/div) v in = 5v, r load = 0 i out (1a/div) v flg (5v/div) current limit response time (100 s/div) v out (2v/div) v in = 5v, c out = 10 f, r load = 4 i out (500ma/div) turn off from en time (100 s/div) v out (2v/div) v en (5v/div) c out = 10 f, r load = 10 i in (500ma/div) flag response time (2ms/div) v out (5v/div) v in = 5v, r load = 4 i out (500ma/div) v flg (5v/div) power off from v in time (2ms/div) v out (2v/div) v in (2v/div) r load = 200 turn on from en time (100 s/div) v out (2v/div) v en (5v/div) c out = 10 f, r load = 10 i in (500ma/div)
RT9721A/b 9 ds9721a/b-02 april 2011 www.richtek.com applications information the RT9721A/b are single n-mosfet high-side power switch with active-high enable input, optimized for self- powered and bus-powered universal serial bus (usb) applications. the RT9721A/b series equipped with a charge pump circuitry to drive the internal n-mosfet switch; the switch's low r ds(on) , 80m , meets usb voltage drop requirements; and a flag output is available to indicate fault conditions to the local usb controller. input and output v in (input) is the power source connection to the internal circuitry and the drain of the mosfet. v out (output) is the source of the mosfet. in a typical application, current flows through the switch from v in to v out toward the load. if v out is greater than v in , current will flow from v out to v in since the mosfet is bidirectional when on. unlike a normal mosfet, there is no a parasitic body diode between drain and source of the mosfet, the RT9721A/b prevent reverse current flow if v out being externally forced to a higher voltage than v in when the chip is disabled (v en < 0.8v). d g s d g s normal mosfet RT9721A/b chip enable input the switch will be disabled when the en pin is in a logic low condition. during this condition, the internal circuitry and mosfet are turned off, reducing the supply current to 0.1 a typical. the maximum guaranteed voltage for a logic low at the en pin is 0.8v. a minimum guaranteed voltage of 2v at the en pin will turn the RT9721A/b on. floating the input may cause unpredictable operation. en should not be allowed to go negative with respect to gnd. soft start for hot plug-in applications in order to eliminate the upstream voltage droop caused by the large inrush current during hot-plug events, the ? soft- start ? feature effectively isolates the power source from extremely large capacitive loads, satisfying the usb voltage droop requirements. fault flag the RT9721A/b series provides a flg signal pin which is an n-channel open drain mosfet output. this open drain output goes low when v out < v in ? 1v, current limit or the die temperature exceeds 150 c approximately. the flg output is capable of sinking a 10ma load to typically 200mv above ground. the flg pin requires a pull-up resistor, this resistor should be large in value to reduce energy drain. a 100k pull-up resistor works well for most applications. in the case of an over-current condition, flg will be asserted only after the flag response delay time, t d , has elapsed. this ensures that flg is asserted only upon valid over- current conditions and that erroneous error reporting is eliminated. for example, false over-current conditions may occur during hot-plug events when extremely large capacitive loads are connected and causes a high transient inrush current that exceeds the current limit threshold. the flg response delay time td is typically 12ms. under-voltage lockout under-voltage lockout (uvlo) prevents the mosfet switch from turning on until input voltage exceeds approximately 2.15v. if input voltage drops below approximately 2.05v, uvlo turns off the mosfet switch, flg will be asserted accordingly. under-voltage detection functions only when the switch is enabled. current limiting protection the current limit circuitry prevents damage to the mosfet switch and the hub downstream port but can deliver load current up to the current limit threshold of typically 700ma through the switch of RT9721A/b series. 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 current limit threshold is exceeded, the device enters constant current mode until the thermal shutdown occurs or the fault is removed.
RT9721A/b 10 ds9721a/b-02 april 2011 www.richtek.com thermal shutdown thermal shutdown is employed to protect the device from damage if the die temperature exceeds approximately 150 c. the power switch will auto-recover when the ic is cooling down. the thermal hysteresis temperature is about 25 c. universal serial bus (usb) & power distribution the goal of usb is to enable devices from different vendors to interoperate in an open architecture. usb features include ease of use for the end user, a wide range of workloads and applications, robustness, synergy with the pc industry, and low-cost implementation. benefits include self-identifying peripherals, dynamically attachable and reconfigurable peripherals, multiple connections (support for concurrent operation of many devices), support for as many as 127 physical devices, and compatibility with pc plug-and-play architecture. the universal serial bus connects usb devices with a usb host: each usb system has one usb host. usb devices are classified either as hubs, which provide additional attachment points to the usb, or as functions, which provide capabilities to the system (for example, a digital joystick). hub devices are then classified as either bus-power hubs or self-powered hubs. a bus-powered hub draws all of the power to any internal functions and downstream ports from the usb connector power pins. the hub may draw up to 500ma from the upstream device. external ports in a bus-powered hub can supply up to 100ma per port, with a maximum of four external ports. self-powered hub power for the internal functions and downstream ports does not come from the usb, although the usb interface may draw up to 100ma from its upstream connect, to allow the interface to function when the remainder of the hub is powered down. the hub must be able to supply up to 500ma on all of its external downstream ports. please refer to universal serial specification revision 2.0 for more details on designing compliant usb hub and host systems. over-current protection devices such as fuses and ptc resistors (also called polyfuse or polyswitch) have slow trip times, high on-resistance, and lack the necessary circuitry for usb-required fault reporting. the faster trip time of the RT9721A/b power distribution allow designers to design hubs that can operate through faults. the RT9721A/b have low on-resistance and internal fault-reporting circuitry that help the designer to meet voltage regulation and fault notification requirements. because the devices are also power switches, the designer of self-powered hubs has the flexibility to turn off power to output ports. unlike a normal mosfet, the devices have controlled rise and fall times to provide the needed inrush current limiting required for the bus-powered hub power switch. supply filter/bypass capacitor a 1uf low-esr ceramic capacitor from vin to gnd, located at the device is strongly recommended to prevent the input voltage drooping during hot-plug events. however, higher capacitor values will further reduce the voltage droop on the input. furthermore, without the bypass capacitor, an output short may cause sufficient ringing on the input (from source lead inductance) to destroy the internal control circuitry. the input transient must not exceed 6.5v of the absolute maximum supply voltage even for a short duration. output filter capacitor a low-esr 150uf aluminum electrolytic or tantalum between vout and gnd is strongly recommended to meet the 330mv maximum droop requirement in the hub vbus (per usb 2.0, output ports must have a minimum 120uf of low-esr bulk capacitance per hub). standard bypass methods should be used to minimize inductance and resistance between the bypass capacitor and the downstream connector to reduce emi and decouple voltage droop caused when downstream cables are hot-insertion transients. ferrite beads in series with vbus, the ground line and the 0.1 f bypass capacitors at the power connector pins are recommended for emi and esd protection. the bypass capacitor itself should have a low dissipation factor to allow decoupling at higher frequencies.
RT9721A/b 11 ds9721a/b-02 april 2011 www.richtek.com voltage drop the usb specification states a minimum port-output voltage in two locations on the bus, 4.75v output of a self-powered hub port and 4.4v output of a bus-powered hub port. as with the self-powered hub, all resistive voltage drops for the bus-powered hub must be accounted for to guarantee voltage regulation (see figure 7-47 of universal serial specification revision 2.0 ). the following calculation determines v out(min) for multiple ports (n ports ) ganged together through one switch (if using one switch per port, n ports is equal to 1) : v out(min) = 4.75v ? [ i i x (4 x r conn + 2 x r cable ) ] ? (0.1a x n ports x r switch ) ? v pcb where r conn : resistance of connector contacts (two contacts per connector) r cable : resistance of upstream cable wires (one 5v and one gnd) r switch : resistance of power switch (80m typical for RT9721A/b) v pcb : pcb voltage drop the usb specification defines the maximum resistance per contact (r conn ) of the usb connector to be 30m and the drop across the pcb and switch to be 100mv. this basically leaves two variables in the equation : the resistance of the switch and the resistance of the cable. if the hub consumes the maximum current (i i ) of 500ma, the maximum resistance of the cable is 90m . the resistance of the switch is defined as follows : r switch = { 4.75v ? 4.4v ? [ 0.5a x (4 x 30m + 2 x 90m )] ? v pcb } / (0.1a x n ports ) = (200mv ? v pcb ) / (0.1a x n ports ) if the voltage drop across the pcb is limited to 100mv, the maximum resistance for the switch is 250m for four ports ganged together. the RT9721A/b, with its maximum 110m on-resistance over temperature, easily meets this requirement. thermal considerations for continuous operation, do not exceed absolute maximum operation junction temperature. the maximum power dissipation depends on the thermal resistance of ic package, pcb layout, the rate of surroundings airflow and temperature difference between junction to ambient. the maximum power dissipation can be calculated by following formula : p d(max) = (t j(max) ? t a ) / ja where t j(max) is the maximum operation junction temperature, t a is the ambient temperature and the ja is the junction to ambient thermal resistance. for recommended operating conditions specification of RT9721A/b, the maximum junction temperature is 125 c. the junction to ambient thermal resistance ja is layout dependent. for sot-23-5 package, the thermal resistance ja is 250 c/w on the standard jedec 51-3 single layer thermal test board. the maximum power dissipation at t a = 25 c can be calculated by following formula : p d(max) = (125 c - 25 c) / (250 c/w) = 0.4w for sot-23-5 package the maximum power dissipation depends on operating ambient temperature for fixed t j(max) and thermal resistance ja . for the RT9721A/b, figure 1 shows the maximum power dissipation allowed under various ambient temperatures. figure 1. maximum power dissipation derating curve 0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45 0.50 0 255075100125 ambient temperature (c) maximum power dissipation (w) single layers pcb sot-23-5
RT9721A/b 12 ds9721a/b-02 april 2011 www.richtek.com layout considerations for best performance of the RT9721A/b series, the following guidelines must be strictly followed. ` input and output capacitors should be placed close to the ic and connected to ground plane to reduce noise coupling. ` the gnd should be connected to a strong ground plane for heat sink. ` keep the main current traces as possible as short and wide. en v in flg v out gnd gnd v in figure 2
RT9721A/b 13 ds9721a/b-02 april 2011 www.richtek.com richtek technology corporation headquarter 5f, no. 20, taiyuen street, chupei city hsinchu, taiwan, r.o.c. tel: (8863)5526789 fax: (8863)5526611 information that is provided by richtek technology corporation is believed to be accurate and reliable. richtek reserves the ri ght to make any change in circuit design, specification or other related things if necessary without notice at any time. no third party intellectual property infringemen t of the applications should be guaranteed by users when integrating richtek products into any application. no legal responsibility for any said applications is assumed b y richtek. richtek technology corporation taipei office (marketing) 5f, no. 95, minchiuan road, hsintien city taipei county, taiwan, r.o.c. tel: (8862)86672399 fax: (8862)86672377 email: marketing@richtek.com outline dimension a a1 e b b d c h l sot-23-5 surface mount package dimensions in millimeters dimensions in inches symbol min max min max a 0.889 1.295 0.035 0.051 a1 0.000 0.152 0.000 0.006 b 1.397 1.803 0.055 0.071 b 0.356 0.559 0.014 0.022 c 2.591 2.997 0.102 0.118 d 2.692 3.099 0.106 0.122 e 0.838 1.041 0.033 0.041 h 0.080 0.254 0.003 0.010 l 0.300 0.610 0.012 0.024

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