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general description the MAX1558/MAX1558h are dual, current-limited switches with autoreset for usb applications. autoreset latches the switch off if it is shorted for more than 20ms, saving system power. the shorted output is then tested to determine when the short is removed to automatically restart the channel. each channel delivers up to 1.2a and meets all iec specifications for usb ports. low quiescent supply current (45?) and standby current (3?) conserve battery power in portable applications. the MAX1558/MAX1558h safety features ensure that the usb port is protected. built-in thermal-overload protection limits power dissipation and junction temperature. accurate, programmable current-limiting circuitry pro- tects the input supply against both overload and short-cir- cuit conditions. 20ms fault blanking enables the circuit to ignore transient faults, such as those caused when hot swapping a capacitive load, preventing false alarms to the host system. the MAX1558/MAX1558h also feature reverse-current protection circuitry to block current flow from the output to the input when the switches are off. the MAX1558/MAX1558h are available in space-sav- ing 3mm x 3mm, 10-pin tdfn packages. the MAX1558 is enabled with an active-low signal, and the MAX1558h is enabled with an active-high signal. applications usb ports and hubs notebook computers and desktops pdas and palmtop computers docking stations features ? 55m ? switch resistance ? tiny 10-pin, 3mm x 3mm tdfn package ? 14% accurate current limit ? autorestart when fault is removed ? programmable current up to 1.2a ? thermal-overload protection ? built-in 20ms fault blanking ? compliant to all usb specifications ? 2.7v to 5.5v supply range ? independent-output fault indicators ? block reverse current when disabled ? 15kv esd protection (with capacitor) ? ul listing pending MAX1558/MAX1558h dual, 3mm x 3mm, 1.2a/programmable-current usb switches with autoreset ________________________________________________________________ maxim integrated products 1 ordering information 19-3128; rev 0; 6/04 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. part temp range pin- package top mark MAX1558 etb -40 c to +85 c 10 tdfn (3mm x 3mm) aar MAX1558h etb -40 c to +85 c 10 tdfn (3mm x 3mm) aas MAX1558 input 2.7v to 5.5v ina inb iset flta fltb ona onb ona onb outa outb gnd usb port a usb port b typical operating circuit 2 3 9 8 tdfn 3mm x 3mm top view 4 5 7 6 1 MAX1558 (MAX1558h) 10 iset ina inb ona (ona) onb (onb) outa gnd outb flta fltb pin configuration
MAX1558/MAX1558h dual, 3mm x 3mm, 1.2a/programmable-current usb switches with autoreset 2 _______________________________________________________________________________________ absolute maximum ratings electrical characteristics (v ina = v inb = 5v, v ona = v onb = 0v (MAX1558), v ona = v onb = 5v (MAX1558h), r iset = 26k ? to gnd, t a = 0? to +85? , unless otherwise noted. typical values are at t a = +25 c.) (note 3) 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_, on_, out_, iset, flt_ to gnd........................-0.3v to +6v in_ to out_ (when disabled) (note 1) ........................-6v to +6v in_ to out_ (when enabled) (note 2) ............-1.6a to +1.6a rms flt_ sink current................................................................20ma continuous power dissipation (t a = +70?) 10-pin tdfn 3mm x 3mm (derate 24.4mw/ c above +70 c) .............................1952mw operating temperature range ...........................-40? to +85? junction temperature ......................................................+160? storage temperature range .............................-65? to +150? lead temperature (soldering, 10s) .................................+300? parameter symbol conditions min typ max units supply voltage range 2.75 5.50 v v in_ = 5v, t a = +25 c5575 v in_ = 3.3v, t a = +25 c64 switch on-resistance r on v in_ = 4.4v, t a = 0 c to +85 c 105 m ? standby supply current both switches disabled 3 6 ? quiescent supply current both switches enabled 45 75 ? v outa = v outb = 0v 0.03 10 out_ off-leakage current switches disabled v outa = v outb = 5v 0.03 ? reverse leakage current v in_ = 0v, v outa = v outb = 5v, both switches disabled 0.03 ? undervoltage-lockout threshold v uvlo rising edge, 3% hysteresis 2.3 2.5 2.7 v continuous load current r iset = 26k ? 1.2 a r iset = 26k ? ? ? ? ? ? ? ? ? flt_ 82040ms turn-on delay t on r out_ = 10 ? , c out_ = 1?, does not include rise time (from on asserted to v out_ = 10% v in_ ) 0.5 1.4 4.0 ms note 1: reverse current (current from out_ to in_) is blocked when disabled. note 2: forward current (current from in_ to out_) is internally limited. reverse current, from out_ to in_, is not limited when the device is enabled and must be kept below 1.5a rms to prevent permanent device damage. when the MAX1558/MAX1558h are disabled, the switch turns off and reverse current is internally blocked.
MAX1558/MAX1558h dual, 3mm x 3mm, 1.2a/programmable-current usb switches with autoreset _______________________________________________________________________________________ 3 electrical characteristics (continued) (v ina = v inb = 5v, v ona = v onb = 0v (MAX1558), v ona = v onb = 5v (MAX1558h), r iset = 26k ? to gnd, t a = 0? to +85? , unless otherwise noted. typical values are at t a = +25 c.) (note 3) parameter symbol conditions min typ max units output rise time t rise c out_ = 1?, r out_ = 10 ? , (from 10% to 90% of v out_ ) 4ms turn-off delay from on t off r out_ = 10 ? , c out_ = 1?, does not include rise time (from on deasserted to v out_ = 90% v in_ ) 100 1000 ? output fall time t fall c out_ = 1?, r out_ = 10 ? (from 90% to 10% of v out_ ) 3ms thermal-shutdown threshold 10 c hysteresis +160 c v in_ = 2.7v to 4.0v 1.6 ona/onb logic input high voltage v ih v in_ 4.0v to 5.5v 2.0 v v in_ = 2.7v to 4.0v 0.6 ona/onb logic input low voltage v il v in_ = 4.0v to 5.5v 0.8 v logic input current v on_ = 0v or v in_ -1 +1 ? flt_ output low voltage i sink = 1ma 0.4 v flt_ output high leakage current v in_ = v flt _ = 5.5v 1 a autorestart current in latched-off state, v out_ = 0v 10 25 50 ma autorestart threshold in latched-off state, rising 0.4 0.5 0.6 v autorestart delay in latched-off state, v out_ > 1v 8 20 40 ms electrical characteristics (v ina = v inb = 5v, v ona = v onb = 0v (MAX1558), v ona = v onb = 5v (MAX1558h), r iset = 26k ? to gnd, t a = -40? to +85? , unless otherwise noted.) parameter symbol conditions min typ max units supply voltage range 2.7 5.5 v v in_ = 5v, t a = +25 c75 switch on-resistance r on v in_ = 4.4v, t a = 0 c to +85 c 105 m ? standby supply current both switches disabled 6 a quiescent supply current both switches enabled 75 ? out_ off-leakage current switches disabled, v outa = v outb = 0v 10 ? undervoltage-lockout threshold v uvlo rising edge, 3% hysteresis 2.3 2.7 v continuous load current r iset = 26k ? 1.2 a r iset = 26k ? 1.20 1.60 r iset = 39k ? ? ? flt_ 840ms
typical operating characteristics (v ina = v inb = 5v, v ona = v onb = 0v (MAX1558), v ona = v onb = 5v (MAX1558h), r iset = 26k ? to gnd. typical values are at t a = +25 c, unless otherwise noted.) MAX1558/MAX1558h dual, 3mm x 3mm, 1.2a/programmable-current usb switches with autoreset 4 _______________________________________________________________________________________ electrical characteristics (continued) (v ina = v inb = 5v, v ona = v onb = 0v (MAX1558), v ona = v onb = 5v (MAX1558h), r iset = 26k ? to gnd, t a = -40? to +85? , unless otherwise noted.) parameter symbol conditions min typ max units turn-on delay t on r out_ = 10 ? , c out_ = 1?, does not include rise time (from on asserted to v out_ = 10% v in_ ) 0.5 4.0 ms turn-off delay from on t off r out_ = 10 ? , c out_ = 1?, does not include rise time (from on deasserted to v out_ = 90% v in_ ) 1000 ? v in_ = 2.7v to 4.0v 1.6 ona/onb logic input high voltage v ih v in_ = 4.0v to 5.5v 2.0 v v in_ = 2.7v to 4.0v 0.6 ona/onb logic input low voltage v il v in_ = 4.0v to 5.5v 0.8 v logic input current v on_ = 0v or v in_ -1 +1 ? flt_ output low voltage i sink = 1ma 0.4 v flt_ output high leakage current v in_ = v flt _ = 5.5v 1 a autorestart current in latched-off state, v out_ = 0v 10 50 ma autorestart threshold in latched-off state, rising 0.4 0.6 v autorestart delay in latched-off state, v out_ > 1v 8 40 ms note 3: specifications from 0 c to -40 c are guaranteed by design but not 100% tested. note 4: the output voltage at which the device transitions from short-circuit current limit to continuous current limit. see the output- current fault protection section. current-limit program vs. r iset MAX1558/58h toc01 r iset (k ? ) current limit (a) 40 48 52 56 44 28 36 32 1.5 1.4 1.3 1.2 1.1 1.0 0.9 0.8 0.7 0.6 1.6 0.5 24 60 quiescent supply current vs. supply voltage MAX1558/58h toc02 supply voltage (v) quiescent current ( a) 5 4 3 2 1 10 20 30 40 50 60 0 06 quiescent current vs. temperature MAX1558/58h toc03 temperature ( c) quiescent current ( a) 60 35 10 -15 35 40 45 50 30 -40 85 v in_ = 5.5v v in_ = 4.5v v in_ = 5v
MAX1558/MAX1558h dual, 3mm x 3mm, 1.2a/programmable-current usb switches with autoreset _______________________________________________________________________________________ 5 shutdown current vs. temperature MAX1558/58h toc04 temperature ( c) shutdown current ( a) 60 35 -15 10 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 0 -40 85 on_ = v in_ (MAX1558) on_ = gnd (MAX1558h) switch off-leakage current vs. temperature MAX1558/58h toc05 temperature ( c) switch off-leakage current (na) 60 35 -15 10 0.01 0.1 1 10 100 1000 -40 85 on_ = in_ (MAX1558) on_ = gnd (MAX1558h) off reverse-blocking leakage current vs. output voltage MAX1558/58h toc06 output voltage (v) off reverse-blocking leakage currrent (na) 5 4 3 2 1 0.1 1 10 100 06 normalized on-resistance vs. temperature MAX1558/58h toc07 temperature ( c) normalized r on ( ? ) 60 35 10 -15 0.75 1.00 1.25 1.50 0.50 -40 85 continuous current-limit threshold vs. temperature MAX1558/58h toc08 temperature ( c) continuous current-limit threshold (a) 60 35 10 -15 1.40 1.42 1.41 1.39 1.38 1.37 1.36 1.44 1.43 1.45 1.35 -40 85 turn-on time vs. temperature (t on + t rise ) MAX1558/58h toc09 temperature ( c) turn-on time (ms) 60 35 10 -15 5 6 7 8 3 4 -40 85 v in_ = 4.5v v in_ = 5.5v v in_ = 5v turn-off time vs. temperature (t off + t fall ) MAX1558/58h toc10 temperature ( c) turn-off time (ms) 60 35 10 -15 2.75 3.00 3.25 3.50 3.75 4.00 2.00 2.25 2.50 -40 85 v in_ = 4.5v v in_ = 5.5v v in_ = 5v MAX1558/58h toc11 temperature ( c) 65 50 35 20 5 -10 -25 22 21 24 23 25 20 -40 80 v in_ = 4.5v v in_ = 5.5v v in_ = 5v fault-blanking time (ms) fault-blanking time vs. temperature MAX1558/58h toc12 temperature ( c) 60 35 10 -15 150 175 200 225 250 275 100 125 -40 85 v in_ = 4.5v v in_ = 5.5v v in_ = 5v fault output low voltage (mv) fault output low voltage vs. temperature typical operating characteristics (continued) (v ina = v inb = 5v, v ona = v onb = 0v (MAX1558), v ona = v onb = 5v (MAX1558h), r iset = 26k ? to gnd. typical values are at t a = +25 c, unless otherwise noted.)
MAX1558/MAX1558h dual, 3mm x 3mm, 1.2a/programmable-current usb switches with autoreset 6 _______________________________________________________________________________________ MAX1558/58h toc13 temperature ( c) 60 35 10 -15 30 32 34 36 38 40 20 26 24 22 28 -40 85 v in_ = 4.5v v in_ = 5.5v v in_ = 5v autoreset current (ma) autoreset current vs. temperature autoreset current vs. input voltage MAX1558/58h toc14 v in (v) autoreset current (ma) 5.5 5.0 4.5 4.0 3.5 25 30 35 40 20 3.0 6.0 t a = +85 c t a = -40 c t a = +25 c overload response into 2.5 ? MAX1558/58h toc15 20ms/div i out_ out_ v in flt_ 5v 5v/div 5v/div 1a/div 0 0 0 short-circuit response into 0 ? MAX1558/58h toc16 20ms/div i out_ v in v out flta_ 5v/div 5v/div 5v/div 5a/div 0 0 0 0 short applied short removed switch on autorestart typical operating characteristics (continued) (v ina = v inb = 5v, v ona = v onb = 0v (MAX1558), v ona = v onb = 5v (MAX1558h), r iset = 26k ? to gnd. typical values are at t a = +25 c, unless otherwise noted.) switch turn-on time MAX1558/58h toc17 2.0ms/div on_ out_ 2v/div 2v/div 0 0 switch turn-off time MAX1558/58h toc18 1.0ms/div on_ out_ 2v/div 2v/div 0 0
detailed description the MAX1558/MAX1558h are dual current-limited switches designed for usb applications. they have two independent switches, each with its own enable control input and autoreset function. each switch has an error- flag output to notify the usb controller when current- limit, short-circuit, undervoltage-lockout, or thermal- shutdown conditions occur (figure 2). the MAX1558/ MAX1558h operate from a 2.7v to 5.5v supply. each output can supply up to 1.2a. current limit for both channels is set with one external resistor. the MAX1558/MAX1558h have independent thermal shutdown for each switch in the event of a prolonged overload. an autoreset function monitors the output and automatically turns the switch on when the overload is removed. separate current limiting and thermal-shut- down circuits permit each switch to operate indepen- dently, improving system robustness. MAX1558/MAX1558h dual, 3mm x 3mm, 1.2a/programmable-current usb switches with autoreset _______________________________________________________________________________________ 7 pin name function 1 ina power input for outa. connect ina and inb together and bypass with a 0.1? capacitor to ground. load conditions may require additional bulk capacitance to prevent the input from being pulled down. 2 ona *(ona) control input for switch a. can be driven higher than in_ without damage. a logic low turns switch a on for the MAX1558. a logic high turns switch a on for the MAX1558h. 3 iset current-limit adjust for both channels. connect a resistor between 26k ? to 60k ? from iset to ground to program the current limit. see setting the current limit in the applications information section. 4 onb *(onb) control input for switch b. can be driven higher than in_ without damage. a logic low turns switch b on for the MAX1558. a logic high turns switch b on for the MAX1558h. 5 inb power input for outb. connect inb and ina together and bypass with a 0.1? capacitor to ground. load conditions may require additional bulk capacitance to prevent the input from being pulled down. 6 outb power output for switch b. connect a 1? capacitor from outb to ground. the load condition may require additional bulk capacitance. 7 fltb fault indicator output for switch b. this open-drain output goes low when switch b is in thermal shutdown or uvlo or in a sustained (>20ms) current-limit or short-circuit condition. 8 gnd ground 9 flta fault indicator output for switch a. this open-drain output goes low when switch a is in thermal shutdown or uvlo or in a sustained (>20ms) current-limit or short-circuit condition. 10 outa power output for switch a. connect a 1? capacitor from outa to ground. the load condition may require additional bulk capacitance. pad exposed pad, internally connected to gnd. connect exposed pad to a large copper trace for maximum power dissipation. pin description * ( ) are for the MAX1558h only. MAX1558 input 2.7v to 5.5v ina inb iset flta fltb ona onb ona onb outa outb gnd usb port a usb port b 0.1 f 100k ? 100k ? 1 f* 1 f* *usb applications may require additional bulk capacitance figure 1. typical application circuit
MAX1558/MAX1558h dual, 3mm x 3mm, 1.2a/programmable-current usb switches with autoreset 8 _______________________________________________________________________________________ MAX1558 charge pump bias uvlo ref osc 25khz timer 20ms thermal shutdown charge pump ilimb ilima 30ma ina ona onb inb iset ona onb fault logic 30ma fltb inb outb gnd outa flta ina 0.6v program ilima program ilimb figure 2. functional diagram
MAX1558/MAX1558h dual, 3mm x 3mm, 1.2a/programmable-current usb switches with autoreset _______________________________________________________________________________________ 9 undervoltage lockout and input voltage requirements the MAX1558/MAX1558h include a uvlo circuit to prevent erroneous switch operation when the input volt- age is low during startup and brownout conditions. operation is inhibited when v in_ is less than 2.5v. output-current fault protection the current limit for both switch outputs is programmed by a resistor between 26k ? and 60k ? connected from iset to ground. see the current-limit program level vs. r iset curve in the typical operating characteristics and setting the current limit in the applications information section. the MAX1558 reduces the gate drive to the mosfet switch when the programmed current-limit value is reached. if the current-limit program value is reached, the part reduces gate drive to regulate at the current limit. if the current limit persists for 20ms (typ), the output turns off and the fault flag is set until the fault is removed, as detected by the autoreset circuit. when the the output drops below 1v (typ), the current limit is set 30% above the programmed level and pulsed. this lowers the rms current for a short-circuit condition, which reduces system load current and power dissipation. if a short circuit persists for 20ms, the output turns off and the fault flag is set. the autore- set circuit automatically restarts the part if the fault is removed. fault blanking the MAX1558/MAX1558h switches can reach current limit in normal operation when powering up or driving heavy capacitive loads. to differentiate these conditions from short circuits or sustained overloads, the MAX1558/MAX1558h have independent fault-blanking circuits in each switch. when a load transient causes the device to enter the current limit, an internal counter monitors the duration of the fault. for load faults exceed- ing the 20ms fault-blanking time, the offending switch turns off, the corresponding flt_ signal asserts low, and that channel enters autoreset mode (see the autoreset mode section). only current-limit and short- circuit faults are blanked. thermal-overload faults and input-voltage drops below the uvlo threshold immedi- ately cause the switch to turn off and flt_ to assert low. fault blanking allows the MAX1558 to handle usb loads that may not be fully compliant with usb specifi- cations. usb loads with additional bypass capacitance and/or large startup currents can be successfully pow- ered even while protecting the upstream power source. no fault is indicated if the switch is able to bring up the load within the 20ms blanking period. autoreset mode if an output fault is detected for more than the 20ms blanking time, the output latches off and the flt_ out- put goes low. the MAX1558/MAX1558h then source 30ma to the faulted output and monitor the output volt- age to determine when the overload is removed. if the voltage on the output rises above 0.5v for more than 20ms, the fault resets and the output turns on. the MAX1558 can also be reset from fault manually by tog- gling on_ (on_ for the MAX1558h) for that channel. reverse current blocking the usb specification does not allow an output device to source current back into the usb port. however, the MAX1558/MAX1558h are designed to safely power noncompliant devices. when disabled, each output is switched to a high-impedance state, blocking reverse- current flow from the output back to the input. however, during normal operation with the device enabled, the MAX1558/MAX1558h are bidirectional switches. thermal shutdown the MAX1558/MAX1558h feature independent thermal shutdown for each switch channel, allowing one switch to deliver power even if the other switch has a fault con- dition. when the junction temperature exceeds +160 c, the switch turns off and the flt_ output goes low imme- diately; fault blanking does not occur during thermal limit. when the junction cools by 10 c, the switch turns on again. if the fault-overload condition continues, the switch cycles on and off, resulting in a pulsed output, saving battery power. fault indicators the MAX1558/MAX1558h provide an open-drain fault output ( flt_ ) for each switch. for most applications, con- nect flt_ to in_ through a 100k ? pullup resistor. flt_ goes low when any of the following conditions occur: the input voltage is below the uvlo threshold. the switch junction temperature exceeds the +160 c thermal-shutdown temperature limit. the switch is in current-limit or short-circuit limit mode after the 20ms fault-blanking period is exceeded. the switch is in autoreset mode. after the fault condition is removed, the flt_ output deasserts after a 20ms delay. ensure that the MAX1558/MAX1558h have adequate input bypass capacitance to prevent glitches from triggering flt_ out- puts. glitches that cause the input supply to drop below 2.5v may cause the undervoltage lockout to trigger, turn- ing the outputs off and asserting the flt signals.
MAX1558/MAX1558h dual, 3mm x 3mm, 1.2a/programmable-current usb switches with autoreset 10 ______________________________________________________________________________________ applications information setting the current limit a resistor from iset to ground programs the current- limit value for both outputs. use a resistor between 26k ? and 86k ? to set the current limit according to the formula: i lim(typical) = 36400 / r iset (amps) do not use r iset values below 26k ? because the maxi- mum current rating of the device may be exceeded. r iset values larger than 60k ? are not recommended and do not provide a lower limit current than 500ma. if the output drops below 1v (typ), the MAX1558 shifts to a short-circuit current-limit threshold that is 30% above the programmed level given by the i lim(typical) formula. if the short-circuit threshold is exceeded, the switch shuts off immediately (no 20ms delay) and ramps the current back up in approximately 3ms. if the short persists and the current ramps all the way up to the short-circuit limit again, the switch again turns off. if the short still persists, the output pulses this way for 20ms, at which time the switch turns off and autoreset mode begins. input capacitor ina and inb provide the power for all control and charge-pump circuitry and must be connected together externally. connect a capacitor from in_ to ground to limit the input-voltage drop during momentary output short-circuit conditions. a 0.1? ceramic capacitor is required for local decoupling; higher capacitor values further reduce the voltage drop at the input. when dri- ving inductive loads, a larger capacitance prevents voltage spikes from exceeding the MAX1558/ MAX1558hs?absolute maximum ratings. output capacitor place a 1? or greater capacitor at each output for noise immunity. when starting up into very large capac- itive loads, the switch may pulse the output current at the short-circuit current-limit program level until the out- put voltage rises above 1v. then, the capacitor contin- ues to charge at the full, continuous current-limit program level. there is no limit to the output capacitor size, but to prevent a startup fault assertion, the capaci- tor must charge up within the fault-blanking delay peri- od. typically, starting up into a 500? or smaller capacitor does not trigger a fault output. in addition to bulk capacitance, small-value (0.1? or greater) ceram- ic capacitors improve the output? resilience to electro- static discharge (esd). driving inductive loads a wide variety of devices (mice, keyboards, cameras, and printers) can load the usb port. these devices com- monly connect to the port with cables, which can add an inductive component to the load. this inductance caus- es the output voltage at the usb port to ring during a load step. the MAX1558/MAX1558h are capable of dri- ving inductive loads, but avoid exceeding the devices absolute maximum ratings. usually the load inductance is relatively small, and the MAX1558/MAX1558hs? input includes a substantial bulk capacitance from an upstream regulator as well as local bypass capacitors, limiting overshoot. if severe ringing occurs due to large load inductance, clamp the MAX1558/MAX1558hs?out- put below +6v and above -0.3v. turn-on and turn-off behavior in the absence of faults, the MAX1558/MAX1558hs internal switches turn on and off slowly under the control of the on_ inputs. transition times for both edges are approximately 4ms. the slow charge-pump switch drive minimizes load transients on the upstream power source. under thermal fault and uvlo, the power device turns off rapidly (100ns) to protect the power device. layout and thermal dissipation to optimize the switch response time to output short- circuit conditions, keep all traces as short as possible to reduce the effect of undesirable parasitic induc- tance. place input and output capacitors no more than 5mm from device leads. all in_ and out_ pins must be connected with short traces to the power bus. wide power-bus planes provide superior heat dissipation through the switch in_ and out_ pins. while the switches are on, power dissipation is small and the package temperature change is minimal. calculate the power dissipation for this condition as follows: p = (i out _) 2 r on for the maximum operating current (i out _ = 1.2a) and the maximum on-resistance of the switch (125m ? ), the power dissipation is: p = (1.2a) 2 x 0.125 ? = 180mw per switch the worst-case power dissipation occurs when the switch is in current limit and the output is greater than 1v. the instantaneous power dissipated in each switch is the voltage drop across the switch multiplied by the current limit. the fault-blanking circuit turns the output off if the fault persists for 20ms, while the autoreset cir- cuit can turn it back on after 20ms in the off state. thus, the average worst-case power is approximately 50% of the instantaneous value. p = 0.5 x (i lim ) x (v in_ - v out_ )
for a 5v input and 1v output, the maximum possible power dissipation per switch is: p = 0.5 x (1.5a) x (5v - 1v) = 3w since the package power dissipation is limited to 1952mw, the MAX1558/MAX1558h die temperature exceeds the thermal-shutdown threshold and the switch turns off. after the die temperature cools by 10 c, the switch turns on again. if the fault-overload condition continues, the switch cycles on and off with a duty cycle and period that is a function of the ambient temperature and pc board layout. a short across the output for more than 20ms places the part in autoreset mode. with v in_ = 5v and an autoreset test current of 30ma, the power dissipation for a short-circuited output is given by: p = (30ma) x 5v = 0.15w MAX1558/MAX1558h dual, 3mm x 3mm, 1.2a/programmable-current usb switches with autoreset ______________________________________________________________________________________ 11 chip information transistor count: 2932 process: bicmos
MAX1558/MAX1558h dual, 3mm x 3mm, 1.2a/programmable-current usb switches with autoreset 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. 12 ____________________maxim integrated products, 120 san gabriel drive, sunnyvale, ca 94086 408-737-7600 2004 maxim integrated products printed usa is a registered trademark of maxim integrated products. package information (the package drawing(s) in this data sheet may not reflect the most current specifications. for the latest package outline info rmation, go to www.maxim-ic.com/packages .) 6, 8, &10l, dfn thin.eps l c l c pin 1 index area d e l e l a e number of leads shown are for reference only e2 detail a n f 1 2 21-0137 package outline, 6, 8, 10 & 14l, tdfn, exposed pad, 3x3x0.80 mm common dimensions symbol min. max. a 0.70 0.80 d 2.90 3.10 e 2.90 3.10 a1 0.00 0.05 l 0.20 0.40 pkg. code n d2 e2 e jedec spec b [(n/2)-1] x e package variations 0.25 min. k a2 0.20 ref. 2.300.10 1.500.10 6 t633-1 0.95 bsc mo229 / weea 1.90 ref f 2 2 21-0137 package outline, 6, 8, 10 & 14l, tdfn, exposed pad, 3x3x0.80 mm 0.400.05 1.95 ref 0.300.05 0.65 bsc 2.300.10 8 t833-1 2.00 ref 0.250.05 0.50 bsc 2.300.10 10 t1033-1 2.40 ref 0.200.03 - - - - 0.40 bsc 1.700.10 2.300.10 14 t1433-1 1.500.10 1.500.10 mo229 / weec mo229 / weed-3 0.40 bsc - - - - 0.200.03 2.40 ref t1433-2 14 2.300.10 1.700.10

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