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general description the max1823 is a dual, current-limited switch with autoreset specifically made for usb applications. the autoreset feature latches the switch off if the output is shorted, saving system power. the switch reactivates when the short circuit is removed. each channel is guar- anteed to supply 720ma and meet usb specifications. low quiescent supply current (50?) and standby current (3?) conserve battery power in portable applications. the max1823 has multiple safety features to ensure that the usb port is protected. built-in thermal-overload protection limits power dissipation and junction temper- ature. accurate internal current-limiting circuitry pro- tects the input supply against both overload and short-circuit conditions. independent fault signals ( faulta and faultb ) notify the microprocessor (?) when a thermal-overload, current-limit, undervoltage- lockout (uvlo), or short-circuit fault occurs. a 20ms fault-blanking feature ignores momentary faults, such as those caused when hot swapping a capacitive load, preventing false alarms to the host system. the max1823a/max1823b also block reverse current (cur- rent from out_ to in_) while in shutdown. the max1823 is available in a space-saving 10-pin ?ax package. the max1823/max1823a are enabled with an active-low signal, and the max1823b/max1823h are enabled with an active-high signal. for a single ver- sion of this device, refer to the max1946 data sheet. for a triple version, refer to the max1940 data sheet. applications usb ports and hubs notebook and desktop computers pdas and palmtop computers docking stations features dual usb switch in tiny 10-pin ?ax package autoreset feature saves power guaranteed 720ma load per channel built-in 20ms fault blanking compliant to usb specification blocks reverse current in shutdown (max1823a/max1823b) 4v to 5.5v input voltage range independent shutdown control (max1823/max1823a?ctive low) (max1823b/max1823h?ctive high) independent fault indicator outputs thermal-overload protection 50? quiescent current (both switches on) 3? standby current ul recognized max1823/max1823a/max1823b/max1823h dual usb switch with fault blanking and autoreset ________________________________________________________________ maxim integrated products 1 ordering information typical operating circuit 19-1903; rev 3; 10/03 part temp range pin-package max1823 eub -40? to +85? 10 ?ax max1823a eub -40? to +85? 10 ?ax max1823b eub -40? to +85? 10 ?ax max1823h eub -40? to +85? 10 ?ax pin configuration onb onb ona ona gnd max1823 max1823a faultb faulta in ina inb usb port a outa usb port b outb input 4v to 5.5v 1 2 3 4 5 10 9 8 7 6 outa gnd outb inb in ina max1823 max1823a max1823b max1823h max top view *(ona) ona *(onb) onb *( ) are for max1823b/max1823h. faultb faulta 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.
max1823/max1823a/max1823b/max1823h dual usb switch with fault blanking and autoreset 2 _______________________________________________________________________________________ absolute maximum ratings 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, ina, inb, ona , onb , ona, onb outa, outb to gnd ...........................................-0.3v to +6v faulta , faultb to gnd..........................-0.3v to (v in_ + 0.3v) max1823/max1823h, ina, in to outa; inb, in to outb ...................................................-0.3v to +6v max1823a/max1823b, ina, in to outa; inb, in to outb (when disabled, note 3)...............-6v to +6v ina, in to outa; inb, in to outb (when enabled, note 4)..............................-1.5a to +1.5a rms faulta , faultb current .................................................20ma continuous power dissipation (t a = +70 c) 10-pin ?ax (derate 5.6mw/ c above +70 c) ...........444mw operating temperature range ...........................-40 c to +85 c junction temperature ......................................................+150 c storage temperature range .............................-65 c to +150 c lead temperature (soldering, 10s) .................................+300 c parameter symbol conditions min typ max units supply voltage range 4.0 5.5 v t a = +25 c, each switch, max1823/max1823h 75 105 t a = +25 c, each switch, max1823a/max1823b 90 120 t a = 0 c to +85 c, each switch, max1823/max1823h 135 switch on-resistance r on t a = 0 c to +85 c, each switch, max1823a/max1823b 165 m ? standby supply current on_ = in_ (max1823/max1823a), on_ = gnd (max1823b/max1823h) 310a i outa = i outb = 0a, one channel on 40 80 quiescent supply current i outa = i outb = 0a, both channels on 50 100 a on_ = in _ ( max 1823/m ax1823a), on _ = gnd (m ax1823b/m ax1823h), v outa = v outb = 0v, t a = +25 o c 0.02 1.00 out_ off-leakage current on_ = in_ (max1823/max1823a), on_ = gnd (max1823b/max1823h), v outa = v outb = 0v, t a = 0 o c to +85 o c 0.02 10.00 a undervoltage-lockout threshold v uvlo rising edge, 3% hysteresis 3.0 3.4 3.8 v continuous load current 720 ma continuous current limit i lim v in - v out_ = 0.5v 0.72 0.90 1.20 a v out_ = 0v (i out pulsing) 0.8 1.2 1.6 a peak short-circuit current limit i short v out_ = 0v (i out pulsing) 0.35 a rms electrical characteristics (circuit of figure 1, v in = v ina = v inb = 5v, ona = onb = gnd (max1823/max1823a), ona = onb = in (max1823b/max1823h), t a = 0 c to +85 c , unless otherwise noted. typical values are at t a = +25 c.)
max1823/max1823a/max1823b/max1823h dual usb switch with fault blanking and autoreset _______________________________________________________________________________________ 3 parameter symbol conditions min typ max units short-circuit detect threshold (note 1) 1 v continuous current-limit blanking timeout period from continuous current-limit condition to fault_ assertion 10 20 35 ms short-circuit blanking timeout period from short-circuit current-limit condition to fault_ assertion 7.5 18 35.0 ms max1823/max1823h 0.5 1.2 4.0 turn-on delay t on r out_ = 10k ? , does not include rise time max1823a/max1823b 0.3 0.8 3.0 ms output rise time t rise r out_ = 10 ? , from 10% to 90% of v out_ 2.5 ms r out _ = 10 ? , does not include fall time (from on_ (max1823) or on_ (max1823h) deasserted to v out = 90% of v in_ ) 0.8 3.0 turn-off delay from on t off r out _ = 10 ? , does not include fall time (from on_ (max1823a) or on_ (max1823b) deasserted to v out = 90% of v in_ ) 0.1 3.0 ms r out_ = 10 ? , from 90% to 10% of v out_ (max1823/max1823h) 2.5 output fall time t fall r out_ = 10 ? , from 90% to 10% of v out_ (max1823a/max1823b) 2.8 ms thermal-shutdown threshold 15 o c hysteresis +160 o c logic input high voltage v in_ = 4v to 5.5v 2 v logic input low voltage v in_ = 4v to 5.5v 0.8 v logic input current on_ = gnd or in_ (max1823/max1823a), on_ = gnd or in_ (max1823b/max1823h) -1 +1 a fault_ output low voltage i sink = 1ma, v in _ = 4v 0.4 v fault_ output high leakage current v in _ = v fault_ = 5.5v 1 a autoreset out_ current in latched-off state, v out_ = 0v 10 30 45 ma autoreset threshold in latched-off state, rising 0.4 0.5 0.6 v autoreset blanking time in latched-off state, v out_ > 0.5v 10 20 35 ms electrical characteristics (continued) (circuit of figure 1, v in = v ina = v inb = 5v, ona = onb = gnd (max1823/max1823a), ona = onb = in (max1823b/max1823h), t a = 0 c to +85 c , unless otherwise noted. typical values are at t a = +25 c.)
max1823/max1823a/max1823b/max1823h dual usb switch with fault blanking and autoreset 4 _______________________________________________________________________________________ electrical characteristics (circuit of figure 1, v in = v in _ = v on _ = 5v (max1823b/max1823h); v in = v in _ = 5v, on_ = gnd (max1823/max1823a), t a = -40 c to +85 c , unless otherwise noted.) (note 2) parameter symbol conditions min typ max units supply voltage range 4.0 5.5 v each switch, max1823/max1823h 135 switch on-resistance r on each switch, max1823a/max1823b 165 m ? standby supply current on_ = in_ (max1823/max1823a), on_ = gnd (max1823b/max1823h) 10 a i outa = i outb = 0a, one channel on 80 quiescent supply current i outa = i outb = 0a, both channels on 100 a out_ off-leakage current on_ = in_ (max1823/max1823a), on_ = gnd (max1823b/max1823h), v outa = v outb = 0v 10 a undervoltage-lockout threshold v uvlo rising edge, 3% hysteresis 3.0 3.8 v continuous load current 720 ma continuous current limit i lim v in_ - v out_ = 0.5v 0.72 1.20 a current limit into short circuit i short v out_ = 0v (i out pulsing) 0.8 1.6 a peak continuous current-limit blanking timeout period from continuous current-limit condition to fault_ assertion 10 35 ms short-circuit blanking timeout period from short-circuit current-limit condition to fault_ assertion 7.5 35.0 ms max1823/max1823h 0.5 4.0 turn-on delay t on r out_ = 10k ? , does not include rise time max1823a/max1823b 0.3 3.0 ms turn-off delay from on t off r out_ = 10 ? , does not include fall time (from on_ (max1823/max1823a) or on_ (max1823b/max1823h) deasserted to v out_ = 90% v in_ ) 3ms
max1823/max1823a/max1823b/max1823h dual usb switch with fault blanking and autoreset _______________________________________________________________________________________ 5 electrical characteristics (continued) (circuit of figure 1, v in = v in _ = v on _ = 5v (max1823b/max1823h); v in = v in _ = 5v, on_ = gnd (max1823/max1823a), t a = -40 c to +85 c , unless otherwise noted.) (note 2) parameter symbol conditions min typ max units logic input high voltage v in_ = 4v to 5.5v 2 v logic input low voltage v in_ = 4v to 5.5v 0.8 v logic input current v on_ = 0v or v in_ -1 +1 a fault_ output low voltage i sink = 1ma, v in_ = 4v 0.4 v fault_ output high leakage current v in_ = v fault_ = 5.5v 1 a autoreset out_current in latched-off state, v out_ = 0v 10 50 ma autoreset threshold in latched-off state, rising 0.4 0.6 v autoreset blanking time in latched-off state, v out_ > 0.5v 10 35 ms note 1: the output voltage at which the device transitions from short-circuit current limit to continuous current limit. note 2: specifications to -40 c are guaranteed by design, not production tested. note 3: reverse current (current from out_ to in_) is blocked when disabled. note 4: 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 max1823a/max1823b are disabled, the switch turns off and reverse current is internally blocked. typical operating characteristics (circuit of figure 1, v in = v ina = v inb = 5v, on _ = gnd (max1823/max1823a), on_ = in_ (max1823b/max1823h), t a = +25 c, unless otherwise noted.) 0 18 12 6 24 30 36 42 48 54 60 02 1 3456 quiescent current vs. input voltage max1823 toc01 input voltage (v) quiescent current ( a) 45 47 51 49 53 55 -40 10 -15 35 60 85 quiescent current vs. temperature max1823 toc02 temperature ( c) quiescent current ( a) v in _ = 5.5v v in _ = 4.5v v in _ = 5v 2.5 2.7 3.1 2.9 3.3 3.5 -40 10 -15 35 60 85 shutdown supply current vs. temperature max1823 toc03 temperature ( c) shutdown supply current ( a) on_ = in_ (max1823/max1823a) on_ = gnd (max1823b/max1823h)
max1823/max1823a/max1823b/max1823h dual usb switch with fault blanking and autoreset 6 _______________________________________________________________________________________ 940 930 920 910 900 -40 10 -15 35 60 85 max1823 toc06 temperature ( c) continuous current limit (ma) continuous current-limit threshold vs. temperature v in_ = 5.5v v in_ = 4.5v v in_ = 5v 0.01 0.1 10 1 100 1000 -40 10 -15 35 60 85 switch off-leakage vs. temperature max1823 toc04 temperature ( c) switch off-leakage (na) 1.50 1.25 1.00 0.75 0.50 -40 10 -15 35 60 85 normalized r on vs. temperature max 1823 toc05 temperature ( c) normalized r on 3.0 3.2 3.6 3.4 3.8 4.0 -40 10 -15 35 60 85 turn-on time vs. temperature (t on + t rise ) max1823 toc07 temperature ( c) turn-on time (ms) v in _ = 5.5v v in _ = 4.5v v in _ = 5v 2.5 2.7 3.1 2.9 3.3 3.5 -40 10 -15 35 60 85 turn-off time vs. temperature (t off + t fall ) max1823 toc08 temperature ( c) turn-off time (ms) v in _ = 5.5v v in _ = 4.5v v in _ = 5v 21.0 21.2 21.6 21.4 21.8 22.0 -40 10 -15 35 60 85 fault-blanking time vs. temperature max1823 toc09 temperature ( c) fault-blanking time (ms) v in _ = 5.5v v in _ = 4.5v v in _ = 5v 0.100 0.150 0.125 0.200 0.175 0.225 0.250 -40 10 -15 35 60 85 fault_ output low voltage vs. temperature max1823 toc10 temperature ( c) fault_ output low voltage (v) v in _ = 5.5v v in _ = 4.5v v in _ = 5v i fault _ = 1ma 15 20 30 25 35 40 -40 10 -15 35 60 85 autoreset current vs. temperature (max1823/max1823h) max1823 toc11 temperature ( c) autoreset current (ma) v in _ = 5.5v v in _ = 4.5v v in _ = 5v 28 30 32 34 36 -40 10 -15 35 60 85 autoreset current vs. temperature (max1823a/max1823b) max1823 toc12 temperature ( c) autoreset current (ma) v in _ = 5.5v v in _ = 4.5v v in _ = 5v typical operating characteristics (continued) (circuit of figure 1, v in = v ina = v inb = 5v, on _ = gnd (max1823/max1823a), on_ = in_ (max1823b/max1823h), t a = +25 c, unless otherwise noted.)
max1823/max1823a/max1823b/max1823h dual usb switch with fault blanking and autoreset _______________________________________________________________________________________ 7 0 10 30 20 40 50 max1823 toc13 input voltage (v) autoreset current (ma) 3.6 5.2 4.4 6.0 autoreset current vs. input voltage (max1823/max1823h) t a = +25 c t a = -40 c t a = +85 c 25 27 29 33 35 31 37 39 max1823 toc14 input voltage (v) autoreset current (ma) 3.6 5.2 4.4 6.0 autoreset current vs. input voltage (max1823a/max1823b) t a = +25 c t a = +85 c t a = -40 c 10ms/div overload response into 2.5 ? (max1823/max1823h) a: v in_ , 5v/div b: v outa , 5v/div c: v faulta , 5v/div d: i outa , 1a/div a b d c max1823 toc15 5v 0 0 0 10ms/div overload response into 2.5 ? (max1823a/max1823b only) a: v in_ , 5v/div b: v outa , 5v/div c: v faulta , 5v/div d: i outa , 1a/div a b d c max1823 toc16 5v 0 0 0 500 s/div overload response into 2.5 ? (expanded time scale) a: v in_ , 5v/div b: v outa , 5v/div a b d c max1823 toc17 5v 0 0 0 c: v faulta , 5v/div d: i outa , 1a/div 10ms/div short-circuit response into 0 ? (max1823/max1823h) a b d c max1823 toc18 5v 0 0 0 c: v faulta , 5v/div d: i outa , 1a/div a: v in _, 5v/div b: v outa , 5v/div 10ms/div short-circuit response into 0 ? (max1823a/max1823b) a b d c max1823 toc19 5v 0 0 0 c: v faulta , 5v/div d: i outa , 2a/div a: v in _, 5v/div b: v outa , 5v/div 500 s/div short-circuit response into 0 ? (expanded time scale) a: v in_ , 5v/div b: v outa , 5v/div a b d c max1823 toc20 5v 0 5v 0 c: v faulta , 5v/div d: i outa , 2a/div 1ms/div switch turn-on time (max1823/max1823a) a: v ona , 5v/div b: v outa , 2v/div a b max1823 toc21 0 0 typical operating characteristics (continued) (circuit of figure 1, v in = v ina = v inb = 5v, on _ = gnd (max1823/max1823a), on_ = in_ (max1823b/max1823h), t a = +25 c, unless otherwise noted.)
max1823/max1823a/max1823b/max1823h dual usb switch with fault blanking and autoreset 8 _______________________________________________________________________________________ pin description pin name function 1 ona *(ona) c ontr ol inp ut for s w i tch a. c an b e d r i ven hi g her than in_ w i thout d am ag e. a l og i c l ow tur ns sw i tch a on for the m ax 1823/m ax 1823a, and a l og i c hi g h tur ns sw i tch a on for the m ax 1823b/m ax 1823h . 2, 3, 4 ina, in, inb power input. connect all in_ pins together, and bypass with a 0.1f capacitor to ground. load conditions may require additional bulk capacitance to prevent the input from being pulled down. 5 onb *(onb) control input for switch b. can be driven higher than in_ without damage. a logic low turns switch b on for the m ax 1823/m ax 1823a, and a logic high turns switch b on for the m ax 1823b/m ax 1823h . 6 faultb 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. 7 outb power output for switch b. connect a 1f capacitor from outb to ground. load condition may require additional bulk capacitance. 8 gnd ground 9 outa power output for switch a. connect a 1f capacitor from outa to ground. load condition may require additional bulk capacitance. 10 faulta 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. 1ms/div switch turn-off time (t off + t fall ) a: v ona , 5v/div b: v outa , 2v/div a b max1823 toc22 0 0 500 s/div startup time (typical usb application) a: v ona , 5v/div b: v faulta , 5v/div a b max1823 toc23 0 5v c d 0 0 c: v outa , 2v/div d : i outa , 0.5a/div typical operating characteristics (continued) (circuit of figure 1, v in = v ina = v inb = 5v, on _ = gnd (max1823/max1823a), on_ = in_ (max1823b/max1823h), t a = +25 c, unless otherwise noted.) * () are for the max1823b/max1823h only.
max1823/max1823a/max1823b/max1823h dual usb switch with fault blanking and autoreset _______________________________________________________________________________________ 9 detailed description the max1823 is a dual, current-limited switch designed for usb applications. it has 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 the current-limit, short-circuit, undervoltage-lockout, or thermal-shutdown threshold is reached (figure 2). the max1823 operates from a 4v to 5.5v input voltage range and guarantees a minimum 720ma output current. a built-in 0.9a current limit limits the current in the event of a heavy-overload condition. the max1823 has inde- pendent thermal shutdown for each switch in the event of a prolonged overload or short-circuit condition. the autoreset function monitors the overload and automati- cally turns the switch on when the overload is removed. use of low-r on nmos switches enables the max1823 to provide two switches in the ultra-small 10-pin max package. an internal micropower charge pump gener- ates the high-side supply needed for driving the gates of these high-side switches. separate current-limiting and thermal-shutdown circuits permit each switch to operate independently, improving system robustness. undervoltage-lockout and input-voltage requirements the max1823 includes a uvlo circuit to prevent erro- neous switch operation when the input voltage goes low during startup and brownout conditions. operation is inhibited when v in_ is less than 3.4v. output fault protection the max1823 senses the switch output voltage and selects continuous current limiting when v out is greater than 1v or short-circuit current limiting when v out is less than 1v. when v out is greater than 1v, the device oper- ates in a continuous current-limit mode that sets the out- put current limit to 0.9a. when v out is less than 1v, the device operates in short-circuit current-limit mode, sourcing 0.35a rms current pulses to the load. autoreset mode if an output fault is detected for more than the 20ms blanking time, the output latches off, the fault_ output goes low, and a 25ma current is forced at the output. if the voltage on the output exceeds 0.5v for 20ms, the fault resets, the 25ma current source shuts down, and the out- put turns on. the device monitors the output voltage so that a short-circuit condition can be detected. active loads are not expected to have measurable currents when the supply is below 0.5v. the max1823/max1823a can also be reset from fault manually by toggling on_ ( on_ for the max1823b/max1823h) for that channel. thermal shutdown the max1823 features independent thermal shutdown for each switch channel, allowing one switch to deliver power even if the other switch has a fault condition. when the junction temperature exceeds +160 c, the switch turns off and the fault_ output goes low imme- diately; fault blanking does not occur during thermal limit. when the junction cools by 15 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. reverse current blocking the usb specification does not allow an output device to source current back into the usb port. however, the max1823a/max1823b 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 max1823a/max1823b are bidirectional switches. fault indicators the max1823 provides an open-drain fault output ( fault_ ) for each switch. for most applications, connect fault_ to in_ through a 100k ? pullup resistor. fault_ 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 fault-blanking period is exceeded. ? the switch is in autoreset mode. onb onb ona ona gnd max1823 faultb faulta in ina inb usb port a outa usb port b outb input 4v to 5.5v 0.1 f 100k ? 100k ? 1 f* * usb applications may require additional bulk capacitance. 1 f* figure 1. typical application circuit
max1823/max1823a/max1823b/max1823h dual usb switch with fault blanking and autoreset 10 ______________________________________________________________________________________ after the fault condition is removed, the fault_ output deasserts after a 20ms delay. ensure that the max1823 has adequate input bypass capacitance to prevent glitches from triggering fault_ outputs. input glitches greater than 0.2v/s may cause erroneous fault_ indications. behavior during current limit and fault blanking the max1823 limits switch current in three ways. when on_ is deasserted (high for max1823/max1823a, low for max1823b/max1823h), the switch is off and leak- age dominates the residual output current. when on_ is asserted (low for max1823/max1823a, high for max1823b/max1823h), the switch supplies a continu- ous output current of at least 720ma. when the output current exceeds the 0.9a threshold, the max1823 lim- its the current depending on the output voltage. for v out_ greater than 1v (current-limit mode), the max1823 regulates the output current to 0.9a. for v out_ less than 1v (short-circuit mode), the max1823 pulses the switch, decreasing the current to 0.35a rms (table 1). note that a thermal overload may result from either of these high-current conditions. the max1823 switches may enter current limit in nor- mal operation when powering up or driving heavy capacitive loads. to differentiate these conditions from short circuits or sustained overloads that may damage the device, the max1823 has an independent fault- blanking circuit in each switch. when a load transient causes the device to enter current limit, an internal counter starts to monitor the duration of the fault. for load faults exceeding 20ms fault-blanking time, the switch turns off, the fault_ signal asserts low, and the device 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 immediately cause the switch to turn off and fault_ to assert low. ona max1823/max1823a max1823b/max1823h charge pump onb charge pump *(ona) *(onb) *( ) are for the max1823b/max1823h. osc 25khz bias uvlo ref gnd 0.1 f 4v to 5.5v in_ timer 20ms thermal shutdown fault logic ilim 25ma 25ma 1 f outa faultb faulta ilim 1 f outb ina ina inb inb figure 2. functional diagram
max1823/max1823a/max1823b/max1823h dual usb switch with fault blanking and autoreset ______________________________________________________________________________________ 11 table 1. max1823 current limiting and fault behavior fault blanking allows the max1823 to handle usb loads that may not be fully compliant with the usb specifica- tions. 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. applications information input power source in, ina, and inb provide the power for all control and charge-pump circuitry. all three in_ pins must be con- nected together externally. the input-voltage slew rate should be less than 0.2v/s to prevent erroneous fault_ indications. this condition should not occur under normal usb applications. input capacitor connect a capacitor from in_ to ground to limit the input voltage drop during momentary output short-circuit con- ditions. a 0.1f ceramic capacitor is required for local decoupling; higher capacitor values further reduce the voltage drop at the input (see the typical application circuit (figure 1)). when driving inductive loads, a larg- er capacitance prevents voltage spikes from exceeding the max1823 s absolute maximum ratings. output capacitor place a 1f or greater capacitor at each output for noise immunity. when starting up into very large capacitive loads, the switch pulses the output current at 0.35a rms until the output voltage rises above 1v, then the capacitor continues to charge at the full 0.9a current limit. there is no limit to the output capacitor size, but to prevent a start- up fault assertion, the capacitor must charge up within the fault-blanking delay period. typically, starting up into a 330f or smaller capacitor does not trigger a fault out- put. in addition to bulk capacitance, small-value (0.1f or greater) ceramic capacitors improve the output s resilience to electrostatic 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 causes the output voltage at the usb port to ring during a load step. the max1823 is capable of driving inductive loads, but avoids exceeding the device s absolute maximum rat- ings. usually the load inductance is relatively small, and the max1823 s input includes a substantial bulk capaci- tance from an upstream regulator as well as local bypass capacitors, limiting overshoot. if severe ringing occurs due to large load inductance, clamp the max1823 s out- put below 6v and above -0.3v. condition max1823 behavior output short circuit (v out < 1v) an output short circuit ramps the current to i short in 2ms to 3ms, the switch shuts off, the blanking timer turns on, fault_ stays high, and the output current pulses at 0.35a rms . removing the short circuit before the 15ms short-circuit blanking timeout period allows the next ramped current pulse to soft-start the output. the fault_ flag stays high. a short circuit exceeding 15ms to 20ms forces fault_ low at 20ms, enables autoreset mode, and sources 25ma at the output. an output voltage above 0.5v for 20ms resets the switch, turns on the output, and forces fault_ high. output overload current (v out > 1v) an output overload regulates the current at i lim (0.9a), and fault_ stays high until the overload is removed, a thermal fault occurs, or the 20ms continuous current-limit timeout period is reached. an overcurrent condition still present at 20ms forces fault_ low, enables autoreset, and sources 25ma at the output. an output voltage above 0.5v for 20ms resets the switch, turns on the output, and forces fault_ high. thermal fault (t j > +160 c) a junction temperature of +160 c immediately forces fault_ low (the blanking timer does not apply to thermal faults) and turns off the switch. the junction cooling 15 c removes the thermal fault condition, enables autoreset mode, and sources 25ma at the output. fault_ remains low while a thermal fault condition is present. an output voltage above 0.5v for 20ms resets the switch, turns on the output, and forces fault_ high.
max1823/max1823a/max1823b/max1823h dual usb switch with fault blanking and autoreset 12 ______________________________________________________________________________________ turn-on and turn-off behavior in the absence of faults, the max1823 s internal switches turn on and off slowly under the control of the on_ inputs. transition times for both edges are provided in the electrical characteristics table. 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 normal operating current (i out_ = 0.5a), and the maximum on-resistance of the switch (135m ? ), the power dissipation is: p = (0.5a) 2 x 0.135 ? = 34mw per switch the worst-case power dissipation occurs when the switch is in current limit and the output is greater than 1v. in this case, the power dissipated in each switch is the voltage drop across the switch multiplied by the current limit: p = (i lim ) (v in - v out ) for a 5v input and 1v output, the maximum power dis- sipation per switch is: p = (1.2a) ( 5v - 1v) = 4.8w since the package power dissipation is only 444mw, the max1823 die temperature exceeds the thermal- shutdown threshold, and the switch output shuts down until the junction temperature cools by 15 c. the duty cycle and period are strong functions of the ambient temperature and the pc board layout. a short circuit at the output causes the power dissipated across the switch and the junction temperature to increase. if the fault condition persists, the thermal- overload-protection circuitry activates, and the output shuts down until the junction temperature decreases by 15 c (see the thermal shutdown section). since the output short-circuit current is 25ma (typ), and with v in_ = 5v, calculate the power dissipation for a short-circuited output as follows: p = (0.025a)(5) = 0.125w chip information transistor count: 3227 process: bicmos
max1823/max1823a/max1823b/max1823h dual usb switch with fault blanking and 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. maxim integrated products, 120 san gabriel drive, sunnyvale, ca 94086 408-737-7600 ____________________ 13 ? 2003 maxim integrated products printed usa is a registered trademark of maxim integrated products. 10lumax.eps package outline, 10l umax/usop 1 1 21-0061 i rev. document control no. approval proprietary information title: top view front view 1 0.498 ref 0.0196 ref s 6 side view bottom view 0 0 6 0.037 ref 0.0078 max 0.006 0.043 0.118 0.120 0.199 0.0275 0.118 0.0106 0.120 0.0197 bsc inches 1 10 l1 0.0035 0.007 e c b 0.187 0.0157 0.114 h l e2 dim 0.116 0.114 0.116 0.002 d2 e1 a1 d1 min - a 0.940 ref 0.500 bsc 0.090 0.177 4.75 2.89 0.40 0.200 0.270 5.05 0.70 3.00 millimeters 0.05 2.89 2.95 2.95 - min 3.00 3.05 0.15 3.05 max 1.10 10 0.60.1 0.60.1 ? 0.500.1 h 4x s e d2 d1 b a2 a e2 e1 l l1 c gage plane a2 0.030 0.037 0.75 0.95 a1 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 .)
e nglish ? ???? ? ??? ? ??? what's ne w p roducts solutions de sign ap p note s sup p ort buy comp any me mbe rs m axim > p roduc ts > p ower and battery m anagement max1823, max1823a, max1823b, max1823h dual usb switch with fault blanking and autoreset quickview technical documents ordering info more information all ordering information notes: other options and links for purchasing parts are listed at: http://www.maxim-ic.com/sales . 1. didn't find what you need? ask our applications engineers. expert assistance in finding parts, usually within one business day. 2. part number suffixes: t or t&r = tape and reel; + = rohs/lead-free; # = rohs/lead-exempt. more: see full data sheet or part naming c onventions . 3. * some packages have variations, listed on the drawing. "pkgc ode/variation" tells which variation the product uses. 4. devices: 1-16 of 16 m ax1823 fre e sam ple buy pack age : type pins footprint drawing code/var * te m p rohs/le ad-fre e ? m ate rials analys is max1823eub+t umax;10 pin;15 mm dwg: 21-0061j (pdf) use pkgcode/variation: u10+2 * -40c to +85c rohs/lead-free: lead free materials analysis max1823eub+ umax;10 pin;15 mm dwg: 21-0061j (pdf) use pkgcode/variation: u10+2 * -40c to +85c rohs/lead-free: lead free materials analysis max1823eub umax;10 pin;15 mm dwg: 21-0061j (pdf) use pkgcode/variation: u10-2 * -40c to +85c rohs/lead-free: no materials analysis max1823eub-t umax;10 pin;15 mm dwg: 21-0061j (pdf) use pkgcode/variation: u10-2 * -40c to +85c rohs/lead-free: no materials analysis m ax1823a fre e sam ple buy pack age : type pins footprint drawing code/var * te m p rohs/le ad-fre e ? m ate rials analys is max1823aeub umax;10 pin;15 mm dwg: 21-0061j (pdf) use pkgcode/variation: u10-2 * -40c to +85c rohs/lead-free: no materials analysis max1823aeub-t umax;10 pin;15 mm dwg: 21-0061j (pdf) use pkgcode/variation: u10-2 * -40c to +85c rohs/lead-free: no materials analysis max1823aeub+t umax;10 pin;15 mm dwg: 21-0061j (pdf) use pkgcode/variation: u10+2 * -40c to +85c rohs/lead-free: lead free materials analysis max1823aeub+ umax;10 pin;15 mm dwg: 21-0061j (pdf) use pkgcode/variation: u10+2 * -40c to +85c rohs/lead-free: lead free materials analysis m ax1823b fre e sam ple buy pack age : type pins footprint drawing code/var * te m p rohs/le ad-fre e ? m ate rials analys is max1823beub+t umax;10 pin;15 mm dwg: 21-0061j (pdf) use pkgcode/variation: u10+2 * -40c to +85c rohs/lead-free: lead free materials analysis max1823beub+ umax;10 pin;15 mm dwg: 21-0061j (pdf) use pkgcode/variation: u10+2 * -40c to +85c rohs/lead-free: lead free materials analysis max1823beub-t umax;10 pin;15 mm dwg: 21-0061j (pdf) use pkgcode/variation: u10-2 * -40c to +85c rohs/lead-free: no materials analysis
max1823beub umax;10 pin;15 mm dwg: 21-0061j (pdf) use pkgcode/variation: u10-2 * -40c to +85c rohs/lead-free: no materials analysis m ax1823h fre e sam ple buy pack age : type pins footprint drawing code/var * te m p rohs/le ad-fre e ? m ate rials analys is max1823heub+t umax;10 pin;15 mm dwg: 21-0061j (pdf) use pkgcode/variation: u10+2 * -40c to +85c rohs/lead-free: lead free materials analysis max1823heub-t umax;10 pin;15 mm dwg: 21-0061j (pdf) use pkgcode/variation: u10-2 * -40c to +85c rohs/lead-free: no materials analysis max1823heub+ umax;10 pin;15 mm dwg: 21-0061j (pdf) use pkgcode/variation: u10+2 * -40c to +85c rohs/lead-free: lead free materials analysis max1823heub umax;10 pin;15 mm dwg: 21-0061j (pdf) use pkgcode/variation: u10-2 * -40c to +85c rohs/lead-free: no materials analysis didn't find what you need? next day product selection assistance from applications engineers parametric search applications help quickview technical documents ordering info more information des c ription key features a pplic ations /u s es key spec ific ations diagram data sheet a pplic ation n otes des ign guides e ngineering journals reliability reports software/m odels e valuation kits p ric e and a vailability samples buy o nline p ac kage i nformation lead-free i nformation related p roduc ts n otes and c omments e valuation kits doc ument ref.: 1 9 -1 9 0 3 ; rev 3 ; 2 0 0 3 -1 1 -1 1 t his page las t modified: 2 0 0 7 -0 6 -1 4 c ontac t us: send us an email c opyright 2 0 0 7 by m axim i ntegrated p roduc ts , dallas semic onduc tor ? legal n otic es ? p rivac y p olic y

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