MAX1922 1a current-limited switch for 2 usb ports ________________________________________________________________ maxim integrated products 1 out 1 2 8 7 out out in in gnd so top view 3 4 6 5 MAX1922 oc en MAX1922 in output out input 2.7v to 5.5v on off gnd oc en t ypical operating circuit 19-2254; rev 1; 12/02 pin configuration ordering information general description the MAX1922 current-limited 70m ? switch with built-in fault blanking provides an accurate, preset 1.4a to 2.1a current limit, making it ideal for dual usb applications. its low quiescent supply current (16?) and standby current (1?) conserve battery power in portable appli- cations. the MAX1922 operates with inputs from 2.7v to 5.5v, making it ideal for both 3v and 5v systems. an overcurrent signal ( oc ) notifies the microprocessor that the internal current limit has been reached. a 10ms overcurrent-blanking feature allows momentary faults (such as those caused when hot-swapping into a capacitive load) to be ignored, thus preventing false alarms to the host system. this blanking also prevents an oc signal from being issued when the device is powering up. the MAX1922 has several safety features to ensure that the usb port is protected. built-in thermal-overload pro- tection limits power dissipation and junction tempera- ture. the device also has accurate internal current- limiting circuitry to protect the input supply against overload. the MAX1922 is offered in a space-saving 8-pin so package and operates over the extended (-40? to +85?) temperature range. applications notebook computers usb ports usb hubs docking stations features ? accurate current limit (1.4a min, 2.1a max) ? 10ms internal oc blanking timeout ? oc blanking during power-up ? 125m ? max high-side mosfet ? short-circuit and thermal protection with overcurrent logic output ? undervoltage lockout ? 16? quiescent supply current ? 1? (max) standby supply current ? 2.7v to 5.5v supply range ? ul recognized: ul# e211935 part temp range pin-package MAX1922esa -40? to +85? 8 so for pricing, delivery, and ordering information, please contact maxim/dallas direct! at 1-888-629-4642, or visit maxim? website at www.maxim-ic.com.
MAX1922 1a current-limited switch for 2 usb ports 2 _______________________________________________________________________________________ absolute maximum ratings electrical characteristics (v in = 5v, t a = 0? to +85?, unless otherwise noted. typical values are at t a = +25?.) stresses beyond those listed under ?bsolute maximum ratings?may cause permanent damage to the device. these are stress rating s only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specificatio ns is not implied. exposure to absolute maximum rating conditions for extended periods may affect device reliability. in, en , oc to gnd...................................................-0.3v to +6v out to gnd ................................................-0.3v to (v in + 0.3v) maximum switch current.........................2.3a (internally limited) out short-circuit to gnd ..........................................continuous continuous power dissipation (t a = +70?) 8-pin so (derate 5.88mw/? above +70?)................471mw operating temperature range (extended) .........-40? to +85? storage temperature range .............................-65? to +150? lead temperature (soldering, 10s) .................................+300? parameter symbol conditions min typ max units operating condition input voltage v in 2.7 5.5 v power switch t a = +25? v in = 4.4v to 5.5v 70 100 v in = 4.4v to 5.5v 125 switch static drain-source on- state resistance r ds ( on ) t a = 0? to +85? v in = 3v 72 150 m ? switch turn-on time t on i load = 400ma 80 200 ? switch turn-off time t off i load = 400ma 3 6 20 ? enable input ( en ) v in = 2.7v to 3.6v 2.0 en high-level input voltage v ih v in = 3.7v to 5.5v 2.4 v en low-level input voltage v il v in = 2.7v to 5.5v 0.8 v en input current v en = v in or gnd -1 1 a startup time v in = 5v, c out = 150? from en driven low to 50% full v out 1ms current limit overload output current i limit force v out to 4.5v 1.4 1.75 2.1 a short-circuit output current i sc out shorted to gnd 1 1.4 a supply current supply current, low-level input v en = v in = v out = 5.5v 0.002 1 a timer not running 16 25 supply current, high-level input i q v en = 0, i out = 0 timer running 35 ? t a = +25? 0.01 2 supply-leakage current v en = v in = 5.5v, v out = 0 t a = 0? to +85? 15 ? undervoltage lockout undervoltage lockout uvlo rising edge, 100mv hysteresis 2.0 2.4 2.6 v overcurrent ( oc ) oc threshold 1.1 a oc output low voltage v ol i sink = 1ma, v in = 3v 0.4 v
MAX1922 1a current-limited switch for 2 usb ports _______________________________________________________________________________________ 3 note 1: specifications to -40? are guaranteed by design, not production tested. electrical characteristics (v in = 5v, t a = -40? to +85?, unless otherwise noted.) (note 1) electrical characteristics (continued) (v in = 5v, t a = 0? to +85?, unless otherwise noted. typical values are at t a = +25?.) parameter symbol conditions min typ max units oc off-state current v in = v oc = 5v 1 a oc blanking timeout period t bl from overcurrent condition to oc assertion 6 10 13 ms thermal shutdown thermal shutdown threshold 165 ? parameter symbol conditions min typ max units operating condition input voltage v in 3.0 5.5 v power switch v in = 4.4v to 5.5v 125 switch static drain-source on-state resistance r ds ( on ) v in = 3v 150 m ? switch turn-on time t on i load = 400ma 200 ? switch turn-off time t off i load = 400ma 1 20 s enable input ( en ) v in = 3.0v to 3.6v 2.0 en high-level input voltage v ih v in = 3.7v to 5.5v 2.4 v en low-level input voltage v il v in = 3.0v to 5.5v 0.8 v en input current v en = v in or gnd -1 1 a current limit overload output current i limit force v out to 4.5v 1.2 2.3 a short-circuit output current i sc out shorted to gnd 1.5 a supply current supply current, low-level input v en = v in = v out = 5.5v 2 a supply current, high-level input i q v en = gnd, i out = 0, timer not running 25 ? supply leakage current v en = v in = 5.5v, v out = gnd 15 ? undervoltage lockout undervoltage lockout uvlo rising edge, 100mv hysteresis 2.0 2.9 v overcurrent ( oc ) oc threshold 1.1 a oc output low voltage v ol i sink = 1ma, v in = 3v 0.4 v oc off-state current v in = v oc = 5v 1 a oc blanking timeout period t bl from overcurrent condition to oc assertion 6 14 ms
MAX1922 1a current-limited switch for 2 usb ports 4 _______________________________________________________________________________________ t ypical operating characteristics (circuit of figure 2, v in = 5v, t a = +25?, unless otherwise noted.) 0 6 4 2 8 10 12 14 16 18 20 0 0.5 2.0 2.5 1.0 1.5 3.0 3.5 4.0 4.5 5.0 5.5 quiescent current vs. input voltage MAX1922 toc01 input voltage (v) quiescent current ( a) i out = 0 v en = 0 14.5 14.0 15.5 15.0 16.5 16.0 17.5 17.0 18.0 -40 -15 10 35 60 85 quiescent current vs. temperature MAX1922 toc02 temperature ( c) quiescent current ( a) v in = 5v v in = 3v i out = 0 100 0.01 off supply current vs. temperature 0.1 1 10 MAX1922 toc03 temperature ( c) off supply current (na) -40 -15 10 35 60 85 en = in out = open 0 40 20 80 60 140 120 100 160 -40 -15 10 35 60 85 turn-on time vs. temperature MAX1922 toc07 temperature ( c) turn-on time ( s) i out = 850ma c out = 0.1 f v in = 3v v in = 5v 4.0 5.5 6.0 5.0 4.5 7.5 7.0 6.5 8.5 8.0 9.0 -40 10 -15 35 60 85 turn-off time vs. temperature MAX1922 toc08 temperature ( c) turn-off time ( s) i out = 850ma c out = 0.1 f v in = 3v v in = 5v 5 7 6 12 8 9 10 11 14 13 15 -40 -15 10 35 60 85 oc blanking timeout vs. temperature MAX1922 toc09 temperature ( c) oc blanking timeout (ms) i out = 1.75a v in = 3v or 5v 100 1000 0.01 off switch current vs. temperature 0.1 1 10 MAX1922 toc04 temperature ( c) off switch current (na) -40 -15 10 35 60 85 en = in v out = 0 -40 -15 35 85 normalized on-resistance vs. temperature MAX1922 toc05 temperature ( c) normalized r on 10 60 0.4 0.7 0.6 0.5 0.9 0.8 1.3 1.2 1.1 1.0 1.4 i out = 850ma 0 0.4 0.2 0.8 0.6 1.0 1.2 0 0.5 2.0 2.5 3.0 3.5 1.0 1.5 4.0 4.5 5.0 normalized output current vs. output voltage MAX1922 toc06 output voltage (v) normalized output current short-circuit current i limit (1.75a)
MAX1922 1a current-limited switch for 2 usb ports _______________________________________________________________________________________ 5 5v 0 0 0 2ms/div MAX1922 toc10 current-limit and oc response v in ac-coupled 100mv/div v out , 5v/div v oc , 5v/div i out , 1a/div 5v 5v 0 0 4 s/div MAX1922 toc11 current-limit response v in ac-coupled 500mv/div v out , 5v/div i out , 2a/div v oc , 5v/div 5v 0 0 0 20 s/div MAX1922 toc12 switch turn-on time v out , 5v/div i out , 500ma/div v oc , 5v/div v en , 5v/div 5v 0 0 0 1 s/div MAX1922 toc13 switch turn-off time v out , 5v/div i out , 500ma/div v oc , 5v/div v en , 5v/div startup time (typical usb application) MAX1922 toc14 1ms/div 0 0 5v 0 full current limit charges capacitor resistor load current short-circuit current limit v out 5v/div v en 5v/div i in 1a/div v oc 5a/div t ypical operating characteristics (continued) (circuit of figure 2, v in = 5v, t a = +25?, unless otherwise noted.)
MAX1922 1a current-limited switch for 2 usb ports 6 _______________________________________________________________________________________ detailed description the MAX1922 p-channel mosfet power switch limits output current to 1.4a min and 2.1a max. when the out- put current increases beyond the current limit (i limit ), the current also increases through the replica switch (i out / 13000). the current-limit error amplifier com- pares the voltage to the internal 1.24v reference and regulates the current back to the i limit (figure 1). these switches are not bidirectional; therefore, the input voltage must be higher than the output voltage. continuous short-circuit protection the MAX1922 is a short-circuit-protected switch. in the event of an output short-circuit condition, the current through the switch is foldback-current-limited to 1a continuous. thermal shutdown the MAX1922 has a thermal shutdown feature. the switch turns off and the oc output goes low immediate- ly (no overcurrent blanking) when the junction tempera- ture exceeds +165?. when the MAX1922 cools 20?, the switch turns back on. if the fault short-circuit condi- tion is not removed, the switch will cycle on and off, resulting in a pulsed output. oc indicator the MAX1922 provides an overcurrent output ( oc ). a 100k ? pullup resistor from oc to in provides a logic control signal. this open-drain output goes low when any of the following conditions occur: ? the input voltage is below the 2.4v undervoltage lockout (uvlo) threshold. ? the die temperature exceeds the thermal shutdown temperature limit of +165?. ? the device is in current limit for greater than 10ms. oc blanking the MAX1922 features 10ms overcurrent blanking. blanking allows brief current-limit faults, including momentary short-circuit faults that occur when hot- swapping a capacitive load, and ensures that no oc is issued during power-up. when a load transient causes the device to enter current limit, an internal counter starts. if the load fault persists beyond the 10ms over- current blanking timeout, the oc output asserts low. ensure that the MAX1922 input is adequately bypassed to prevent input glitches from triggering spurious oc outputs. input voltage glitches less than 150mv will not pin description MAX1922 p p p out gnd 1.24v n on current-limit amplifier replica amplifier on en hot in control circuitry oc 10ms timer figure 1. functional diagram pin name function 1 gnd ground 2, 3 in input. p-channel mosfet source?onnect all in pins together and bypass with a 1? capacitor ground. 4 en active-low switch enable input. a logic-low turns on the switch. 5 oc overcurrent-indicator output. this open-drain output goes low when the device is in thermal shutdown or undervoltage lockout, or during a sustained (10ms) current-limit condition. 6, 7, 8 out switch output. p-channel mosfet drain?onnect all out pins together and bypass with a 0.1? capacitor to ground.
MAX1922 1a current-limited switch for 2 usb ports cause a spurious oc output. load-transient faults less than 10ms (typ) will not cause an oc output assertion. only current-limit faults are blanked. die overtempera- ture faults and input voltage droops below the uvlo threshold will cause an immediate oc output. applications information input capacitor to limit the input voltage drop during momentary output short-circuit conditions, connect a capacitor from in to gnd. a 1? ceramic capacitor will be adequate for most applications; however, higher capacitor values will further reduce the voltage drop at the input (figure 2). output capacitor connect a 0.1? capacitor from out to gnd. this capacitor helps to prevent inductive parasitics from pulling out negative during turn-off. layout and thermal dissipation important: optimize the switch response time to output short-circuit conditions by keeping all traces as short as possible to reduce the effect of undesirable parasitic inductance. place input and output capacitors as close as possible to the device (no more than 5mm away). all in and out pins must be connected with short traces to the power bus. wide power-bus planes will provide superior heat dissipation through the MAX1922? in and out pins. under normal operating conditions, the package can dissipate and channel heat away. calculate the maxi- mum power dissipation as follows: p = (i limit ) 2 ? r on where i limit is the preset current limit (2.1a max) and r on is the on-resistance of the switch (125m ? max). when the output is short circuited, foldback-current lim- iting activates and the voltage drop across the switch equals the input supply voltage. the power dissipated across the switch increases, as does the die tempera- ture. if the fault condition is not removed, the thermal- overload protection circuitry activates (see thermal shutdown section). wide power-bus planes connected to in and out and a ground plane in contact with the device help dissipate additional heat. driving inductive loads a wide variety of devices (mice, keyboards, cameras, and printers) can load the usb port. these devices commonly connect to the port with cables, which can add an inductive component to the load. this induc- tance causes the output voltage at the usb port to ring during a load step. the MAX1922 is capable of driving inductive loads, but avoid exceeding the device? absolute maximum ratings. usually the load inductance is relatively small, and the MAX1922 input includes a substantial bulk capacitance from an upstream regula- tor as well as local bypass capacitors, limiting over- shoot. if severe ringing occurs due to large load inductance, clamp the MAX1922 output below 6v and above -0.3v. figure 2. typical application circuit MAX1922 in output out input 1 f 0.1 f * * usb specifications require a higher value capacitor. overcurrent output on 100k ? off gnd oc en chip information transistor count: 715 process: bicmos _______________________________________________________________________________________ 7
MAX1922 1a current-limited switch for 2 usb ports maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a maxim product. no circu it patent licenses are implied. maxim reserves the right to change the circuitry and specifications without notice at any time. 8 _____________________maxim integrated products, 120 san gabriel drive, sunnyvale, ca 94086 408-737-7600 2002 maxim integrated products printed usa is a registered trademark of maxim integrated products. package information soicn .eps package outline, .150" soic 1 1 21-0041 b rev. document control no. approval proprietary information title: top view front view max 0.010 0.069 0.019 0.157 0.010 inches 0.150 0.007 e c dim 0.014 0.004 b a1 min 0.053 a 0.19 3.80 4.00 0.25 millimeters 0.10 0.35 1.35 min 0.49 0.25 max 1.75 0.050 0.016 l 0.40 1.27 0.394 0.386 d d min dim d inches max 9.80 10.00 millimeters min max 16 ac 0.337 0.344 ab 8.75 8.55 14 0.189 0.197 aa 5.00 4.80 8 n ms012 n side view h 0.244 0.228 5.80 6.20 e 0.050 bsc 1.27 bsc c h e e b a1 a d 0 -8 l 1 variations:
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