lnd 3526 dual usb power control switch data sheet general description ? usb specification compliant ? over-current protection ? 2 independent switches ? 140 m ? maximum on-resistance ? thermal shutdown ? 5 a maximum standby supply current ? 2.4v typical under-voltage lockout (uvlo) ? 3v to 5.5v input ? active-high or active-low enable versions ? independent open drain fault flag pins ? 500ma continuous load current per switch features the LND3526, is a dual high side power control switch, with independent enable and flag functions optimized for self powered and bus- powered universal serial bus (usb) applications. the LND3526 satisfies the following usb requirements: each switch channel supplies up to 500ma with internal circuitry limiting the fault current to 750ma. the switch?s 140m ? on- resistance meets usb voltage drop requirements. a flag output is available to indicate fault conditions to the local usb controller. additional features include: lockout (uvlo) to ensure that the device remains off until there is a valid input voltage present, thermal shutdown to prevent switch failure from high current loads and 3.3v and 5v logic compatible enable inputs. the LND3526 is available in active-high and active-low versions in 8-pin die and soic packages. applications ? usb host and self powered hubs ? usb bus-powered hubs ? usb monitors, printers, cameras and other usb controlled peripherals ? hot plug-in power supplies ? battery charger circuits ? linear dimensions, inc. ? 445 east ohio street, chicago il 60611 usa ? tel 312.321.1810 ? fax 312.321.1830 ? www.lineardimensions.com ?
absolute maximum ratings parameter symbol ratings units input supply voltage v in +6 v fault flag voltage v flg +6 v fault flag current i flg 50 ma output voltage v out +6 v output current i out internally limited ma enable input voltage v en -0.3 to + 5.5 v storage temperature t stg -65 to +150 c operating ambient temperature t a -40 to +85 c t a =25 c, v in = +5v; unless specified parameter symbol conditions min typ max units i ddoff all switches off out= open (note 3) 0.75 5 a supply current i ddon all switches on out=open (note 3) 110 160 a v entl high to low transition (turn ?on) 0.8 1.90 v enable input threshold (active low) v enth low to high transition (turn-off) 2.1 2.4 v enable input current i en v en = 0v to 5.5v -1 0.01 1 a enable input capacitance c en 1pf 5v 100 140 switch resistance r on each switch on i out = 500ma 3.3v 140 180 m ? output turn-on delay t on rl=10 ? each output 0.5 ms output turn-on rise time t r rl=10 ? each output 1ms output turn-off delay t off rl=10 ? each output 120 s output turn-off fall time t f rl=10 ? each output 120 s output leakage current i ol output disabled, each output 10 a continuous load current i out each output 0.5 a short circuit current limit i scl enable into load, vout = 4.0v 0.5 0.75 1.25 a current limit threshold i lth ramped load to enabled output vout<4.0v 1.6 2.2 a over temperature shutdown threshold o tth tj(junction temp) :increasing :decreasing 135 125 c c error flag output resistance r flg vin=5v, il=10ma vin+3.3v,il=10ma 10 15 25 40 ? ? error flag off current i flg v flg =5v 0.01 1 a under voltage lockout threshold uvlo vin= increasing vin= decreasing 2.5 2.3 v note 1. exceeding the absolute maximum rating may damage the device note 2. the device is not guaranteed to function outside its operating rating note 3. off is 0.8 and on is 2.4v for the LND3526-1. off is 2.4v and is 0.8v for the LND3526-2. the enable input has approximately 200mv of hysteresis. absolute maximum ratings (note 1) electrical characteristics lnd 3526 ? linear dimensions, inc. ? 445 east ohio street, chicago il 60611 usa ? tel 312.321.1810 ? fax 312.321.1830 ? www.lineardimensions.com ?
lnd 3526 functional description input and output in is power supply connection to the logic circuitry and the drain of the output mosfet. in a typical circuit, current flows from in to out toward the load. if v out is greater that v in , current will flow form out to in, since the switch is bi-directional when enabled. the output mosfet and driver circuitry are also designed to allow the mosfet source to be externally forced to a higher voltage than the drain (vout >vin) when the switch is disabled. in this situation, the LND3526 prevents undesirable current flow from out to in. thermal shutdown thermal shutdown is employed to protect the device from damage should the die temperature exceed safe margins due mainly to short circuit faults. each channel employs its own thermal sensor. thermal shutdown shuts off the output mosfet and asserts the flg output if the die temperature reaches 135 c. the other channel is not effected. the LND3526 will automatically reset its output when the die temperature cools down to 125 c. the LND3526 output and flg signal will continue to cycle on and off until the device is disabled or the fault is removed. depending on pcb layout, package, ambient temperature etc., it may take several hundred milliseconds from the incidence of the fault to the output mosfet being shut off. current-limit response the current-limit threshold is present internally. the preset level prevents damage to the output mosfet and external load but allows a minimum current of 0.5a through the output mosfet of each channel. the current-limit circuit senses a portion of the output fet switch current. the reaction to an overcurrent condition varies with three scenarios: (i) switch enabled into short circuit if a switch is powered on or enabled into a heavy load of short circuit, the switch immediately goes into constant-current mode, reducing the output voltage. the fault flag goes low until the load is reduced. (ii) short circuit applied to output when a heavy load is applied, a large transient current may flow until the current limit circuitry will respond. once this occurs, the device limits current to less than the short-circuit current limit specification. (iii) current-limit response the LND3526 current-limit profile exhibits a small foldback effect of approximately 500ma. once this current-limit threshold is exceeded the device enters constant-current mode. this constant current is specified as the short circuit current limit in the ?electrical characteristics ? table. it is important to mote that the device will deliver load current up to the current-limit threshold, which is typically 1.6a fault flag flg is an n-channel, open-drain mosfet output. the fault-flag is active (low) for one or more of the following conditions: undervoltage (while 2v enable input as with any logic input, the enable pins, ena/enb, must be driven to definitive logic state at all times. floating the input can result in spurious operation. do not drive ena/enb below gnd. fault flag output soft start the LND3526 provides a ?soft-start? function that ramps up the on-current to eliminate any excessive voltage drop that could occur due to charging a capacitive load in bus-powered applications. the ?soft-start?results from a switch on resistance, r on, that is ramped down from high impedance to 140m ? in milliseconds. this r on ramping reduces the inrush current and related transients occur when charging capacitive loads; a requirement for meeting the usb voltage drop standards for bus-powered applications. lnd 3526 applications information supply filtering ldi recommends the use of a 0.1 f to 1 f bypass capacitor to control transients on he power supply pin. the lack of suitable bypassing can result in ringing on the in input when transients occur. this ringing, due to supply lead inductance, could damage LND3526 control circuitry if the 5.5v maximum input rating is exceeded. o 3v to 5.5v 0.1 f to 1 f LND3526 in gnd timing diagrams out p ut rise and fall times 10% 90% 10% 90% t t r f vout ? linear dimensions, inc. ? 445 east ohio street, chicago il 60611 usa ? tel 312.321.1810 ? fax 312.321.1830 ? www.lineardimensions.com ?
typical characteristics (temp : 25 c t vout on t 10% 90% off 50% v en v 90% off t vout en 50% 10% t on active-low switch delay times active-hi g h switch dela y times lnd 3526 ? linear dimensions, inc. ? 445 east ohio street, chicago il 60611 usa ? tel 312.321.1810 ? fax 312.321.1830 ? www.lineardimensions.com ? supply on-current v/s input voltage current( a) 50 100 150 0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 input voltage (v) 2.5 3.0 3.5 4.0 4.5 5.0 5.5 input voltage (v) 100 150 200 50 resistance (m ) ? on-resistance v/s input voltage
lnd 3526 0.5 2.0 0 input voltage (v) 4.0 4.5 1.5 1.0 3.0 enable threshold (v) 3.0 5.5 5.0 3.5 2.5 2.5 turn on turn off 5.0 5.5 6 2.5 4 12 3.0 3.5 4.5 10 8 delay time ( s) input voltage (v) 2 0 4.0 enable threshold v/s input voltage flag delay v/s input voltage functional characteristics v out active low enable input error flag thermal shutdown ? linear dimensions, inc. ? 445 east ohio street, chicago il 60611 usa ? tel 312.321.1810 ? fax 312.321.1830 ? www.lineardimensions.com ?
lnd 3526 turn-on with 47 ? /10 f load turn-on with 47 ? /150 f load turn-off with 47 ? /10 f load turn-off with 47 ? /10 f load active low enable in p ut v out active low enable in p ut active low enable in p ut active low enable in p ut v out v out v out ? linear dimensions, inc. ? 445 east ohio street, chicago il 60611 usa ? tel 312.321.1810 ? fax 312.321.1830 ? www.lineardimensions.com ?
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