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 140mΩ 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 mΩ maximum on-resistance Thermal shutdown 5µA 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 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 Ratings Units VIN VFLG IFLG VOUT IOUT VEN TSTG +6 +6 50 +6 Internally limited -0.3 to + 5.5 -65 to +150 V V mA V mA V TA -40 to +85 °C °C ELECTRICAL CHARACTERISTICS TA =25° C, VIN = +5V; unless specified Parameter Supply Current ENABLE Input Threshold (active Low) Symbol Conditions Min Typ Max Units IDDOFF All Switches OFF OUT= Open (note 3) 0.75 5 µA IDDON All switches ON OUT=Open (note 3) 110 160 µA VENTL VENTH High to Low Transition (Turn –on) Low to High Transition (Turn-off) VEN = 0V to 5.5V 0.8 1.90 V 2.1 2.4 V 1 µA pF ENABLE Input Current ENABLE Input Capacitance IEN CEN Switch resistance RON Each switch ON IOUT= 500mA Output Turn-on Delay TON RL=10Ω each output ±0.01 1 100 140 0.5 TR RL=10Ω each output 1 TOFF RL=10Ω each output 1 20 RL=10Ω each output Output disabled, each output Each output ENABLE into Load, VOUT = 4.0V Ramped load to enabled output VOUT<4.0V 1 20 µs 10 Output Turn-on Rise Time Output Turn-off Delay Output Turn-off Fall time TF -1 5V 3.3V ms ms µs 0.75 1.25 1.6 2.2 A IOL IOUT ISCL Current Limit Threshold ILTH Over Temperature Shutdown Threshold OTTH TJ(Junction temp) :Increasing :Decreasing 135 125 Error Flag Output Resistance RFLG VIN=5V, IL=10mA VIN+3.3V,IL=10mA 10 15 Error Flag Off Current mΩ µA A A Output Leakage Current Continuous Load Current Short Circuit Current Limit 0.5 0.5 140 180 °C °C 25 40 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. Ω Ω µA 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 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 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<Vin<2.7), current limit, or thermal shutdown. Undervoltage Lockout UVLO (undervoltage lockout) prevents the output MOSFET from turning on until VIN exceeds approximately 2.5V. In the undervoltage state, the FLAG will be low. After the switch turns on, if the voltage drops below approximately 2.3V, UVLO shuts off the output MOSFET and signals fault flag. Undervoltage detection functions only when at least one switch is enabled. • Linear Dimensions, Inc. • 445 East Ohio Street, Chicago IL 60611 USA • tel 312.321.1810 • fax 312.321.1830 • www.lineardimensions.com • 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. Supply Filtering LDI recommends the use of a 0.1µF to 1µF 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. 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 140mΩ 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. O 3V to 5.5V LND3526 IN GND 0.1µF to 1µF TIMING DIAGRAMS t F t R 90% 90% 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% t tON OFF 90% Vout 10% Active-Low Switch Delay Times VEN 50% tON t OFF 90% Vout 10% Active-High Switch Delay Times TYPICAL CHARACTERISTICS (Temp : 25 °C On-Resistance v/s Input Voltage Supply On-Current v/s Input Voltage 200 RESISTANCE (m Ω ) 150 150 CURRENT( µ A) 100 50 50 0 2.5 100 3.0 3.5 4.0 4.5 INPUT VOLTAGE (V) 5.0 5.5 2.5 3.0 3.5 4.0 4.5 5.0 5.5 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 Enable Threshold v/s Input Voltage 12 3.0 10 2.5 ENABLE THRESHOLD (V) DELAY TIME ( µ s) Flag Delay v/s Input Voltage 8 6 4 2 Turn OFF 2.0 Turn ON 1.5 1.0 0.5 0 0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 2.5 INPUT VOLTAGE (V) 3.0 3.5 4.0 4.5 5.0 5.5 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 Ω/10 µF Load Turn-On with 47 Ω/150 µF Load Active Low Enable Input Active Low Enable Input VOUT VOUT Turn-Off with 47 Ω/10 µF Load Turn-Off with 47 Ω/10 µF Load • Linear Dimensions, Inc. • 445 East Ohio Street, Chicago IL 60611 USA • tel 312.321.1810 • fax 312.321.1830 • www.lineardimensions.com •