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| DATA SHEET LND 3526 DUAL USB POWER CONTROL SWITCH GENERAL DESCRIPTION The LND3526, is a dual high side power control switch, with independent enable and flag functions optimized for self powered and buspowered 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 onresistance 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. FEATURES * * * * * * * * * * * USB specification compliant Over-Current Protection 2 independent switches 140 m maximum on-resistance Thermal shutdown 5A 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 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 * LND 3526 ABSOLUTE MAXIMUM RATINGS (note 1) Parameter Input Supply Voltage Fault Flag Voltage Fault Flag Current Output Voltage Output Current ENABLE Input Voltage Storage Temperature Operating Ambient Temperature Symbol VIN VFLG IFLG VOUT IOUT VEN TSTG TA Ratings +6 +6 50 +6 Internally limited -0.3 to + 5.5 -65 to +150 -40 to +85 Units V V mA V mA V C C Absolute Maximum Ratings ELECTRICAL CHARACTERISTICS TA =25 C, VIN = +5V; unless specified Parameter Supply Current Symbol IDDOFF IDDON ENABLE Input Threshold (active Low) ENABLE Input Current ENABLE Input Capacitance Switch resistance Output Turn-on Delay Output Turn-on Rise Time Output Turn-off Delay Output Turn-off Fall time Output Leakage Current Continuous Load Current Short Circuit Current Limit Current Limit Threshold Over Temperature Shutdown Threshold Error Flag Output Resistance Error Flag Off Current VENTL VENTH IEN CEN RON TON TR TOFF TF IOL IOUT ISCL ILTH OTTH RFLG Conditions All Switches OFF OUT= Open (note 3) All switches ON OUT=Open (note 3) High to Low Transition (Turn -on) Low to High Transition (Turn-off) VEN = 0V to 5.5V Each switch ON IOUT= 500mA RL=10 each output RL=10 each output RL=10 each output RL=10 each output Output disabled, each output Each output ENABLE into Load, VOUT = 4.0V Ramped load to enabled output VOUT<4.0V TJ(Junction temp) :Increasing :Decreasing VIN=5V, IL=10mA VIN+3.3V,IL=10mA 5V 3.3V 0.8 Min Typ 0.75 110 1.90 2.1 -1 0.01 1 100 140 0.5 1 1 1 0.5 0.5 20 20 10 0.75 1.6 135 125 10 15 25 40 1.25 2.2 2.4 1 140 180 Max 5 160 Units A A V V A pF m ms ms s s A A A A C C A V IFLG VFLG=5V 0.01 1 VIN= increasing 2.5 Under Voltage Lockout UVLO Threshold VIN= decreasing 2.3 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. * 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 Vout is greater that VIN , 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 135C. The other channel is not effected. The LND3526 will automatically reset its output when the die temperature cools down to 125C. 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 LND 3526 APPLICATIONS INFORMATION 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, RON, that is ramped down from high impedance to 140m in milliseconds. This RON 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. Supply Filtering LDI recommends the use of a 0.1F to 1F 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 LND3526 IN GND 0.1F to 1F TIMING DIAGRAMS t R 90% 90% t F Vout 10% 10% Output Rise and Fall Times * Linear Dimensions, Inc. * 445 East Ohio Street, Chicago IL 60611 USA * tel 312.321.1810 * fax 312.321.1830 * www.lineardimensions.com * LND 3526 VEN 50% tON 90% t OFF Vout 10% Active-Low Switch Delay Times VEN 50% tON 90% t OFF Vout 10% Active-High Switch Delay Times TYPICAL CHARACTERISTICS Supply On-Current v/s Input Voltage 150 (Temp : 25 C On-Resistance v/s Input Voltage 200 100 CURRENT( A) RESISTANCE (m ) 150 50 100 0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 50 2.5 3.0 3.5 4.0 4.5 5.0 5.5 INPUT VOLTAGE (V) INPUT VOLTAGE (V) * Linear Dimensions, Inc. * 445 East Ohio Street, Chicago IL 60611 USA * tel 312.321.1810 * fax 312.321.1830 * www.lineardimensions.com * LND 3526 Flag Delay v/s Input Voltage 12 3.0 Enable Threshold v/s Input Voltage 10 2.5 ENABLE THRESHOLD (V) DELAY TIME ( s) 8 2.0 Turn OFF Turn ON 6 1.5 4 1.0 2 0.5 0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 INPUT VOLTAGE (V) INPUT VOLTAGE (V) FUNCTIONAL CHARACTERISTICS Active Low Enable Input Error Flag VOUT 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 Active Low Enable Input Active Low Enable Input VOUT VOUT Turn-On with 47 /10 F Load Turn-On with 47 /150 F Load Active Low Enable Input Active Low Enable Input VOUT VOUT Turn-Off with 47 /10 F Load Turn-Off with 47 /10 F Load * 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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