LM3544 LM3544 Quad Port USB Power Distribution Switch and Over-Current Protection Literature Number: SNVS062B
LM3544 Quad Port USB Power Distribution Switch and Over-Current Protection General Description Features The LM3544 is a quad high-side power switch that is an excellent choice for use in Root, Self-Powered and BusPowered USB (Universal Serial Bus) Hubs. Independent port enables, flag signals to alert USB controllers of error conditions, controlled start-up in hot-plug events, and short circuit protection all satisfy USB requirements. n n n n n n The LM3544 accepts input voltages between 2.7V and 5.5V.
LM3544 Connection Diagrams LM3544-H 16-Pin SOIC LM3544-L 16-Pin SOIC 10120802 10120829 Top View Top View Ordering Information Part Number Enable, Delivery Option LM3544M-H Active High Enable LM3544M-L Active Low Enable LM3544MX-H Active High Enable, 2500 units per reel LM3544MX-L Active Low Enable, 2500 units per reel Package Type SO-16 NS Package Number M16A Typical Application Circuit 10120804 FIGURE 1. The LM3544 used in a Self-Powered or Root USB Hub www.national.
Lead Temperature Range (Soldering, 5 sec.) If Military/Aerospace specified devices are required, please contact the National Semiconductor Sales Office/ Distributors for availability and specifications. Voltage at INX and OUTX pins (Note 2) ESD Rating (Note 3) −0.3V to 6V 2 kV Operating Ratings −0.3V to 5.5V Voltage at ENX(ENX) and FLAGX pins Power Dissipation 260˚C Supply Voltage Range Internally Limited Maximum Junction Temperature Storage Temperature Range 2.7V to 5.
LM3544 AC Electrical Characteristics Limits are for TJ = 25˚C and VIN = 5.0V. Symbol Parameter Conditions Min Typ Max Units tr OUTx Rise Time (Note 5) CL = 33 µF, ILOAD = 500 mA 1.5 ms tf OUTx Fall Time (Note 6) CL = 33 µF, ILOAD = 500 mA 0.9 ms tON Turn-on Delay (Note 7) CL = 33 µF, ILOAD = 500 mA 2.9 ms tOFF Turn-off Delay (Note 8) CL = 33 µF, ILOAD = 500 mA 0.
VIN = 5.0, IOUT_X = 500mA, TA = 25˚C unless otherwise speci- RON vs Input Voltage RON vs Junction Temperature 10120806 10120805 Quiescent Current, Output(s) Enabled vs Junction Temperature Quiescent Current, Output(s) Disabled vs Junction Temperature 10120808 10120807 Quiescent Current, Output(s) Enabled vs Input Voltage Quiescent Current, Output(s) Disabled vs Input Voltage 10120810 10120809 5 www.national.com LM3544 Typical Performance Characteristics fied.
LM3544 Typical Performance Characteristics VIN = 5.0, IOUT_X = 500mA, TA = 25˚C unless otherwise specified.
Turn-On/Turn-Off Response with 47Ω/33µF Load Turn-On/Turn-Off Response with 10Ω/33µF Load 10120818 10120819 Enable Into a Short (Note 10) Short Connected to Enabled Device (Note 10) 10120820 10120821 Over-Current Response with Ramped Load on OUT1 and Fixed Load on OUT2 (Note 10) Inrush Current to Downstream Device when LM3544 is Enabled (Note 11) 10120822 10120823 Note 10: Output is shorted to Ground through a 100 mΩ resistor.
LM3544 rapidly discharge through the part, activating current limit circuitry. The threshold for activating current limiting is 2.0A (typ.). Protection is achieved by momentarily opening the MOSFET switch and then gradually turning it on. Turn-on is halted when the current through the switch reaches the current-limit level of 1.0A (typ.) The current is held at this level until either the excessive load/short is removed or the part overheats and thermal shutdown occurs (see Thermal Shutdown section, below).
SOFT START (Continued) When a power switch is enabled, high levels of current will flow instantaneously through the LM3544 to charge the large capacitance at the output of the port. This is likely to exceed the over-current threshold of the device, at which point the LM3544 will enter its current-limit mode. The amount of current used to charge the output capacitor is then set by the current-limit circuitry.
LM3544 Application Information (1) PD = RON * IDS2 Note: Equation for power dissipation neglects portion that comes from LM3544 quiescent current because this value will almost always be insignificant. Using this figure, determine the junction temperature with Equation (2). (2) TJ = PD * θJA + TA. (Continued) tantalum capacitor is recommended. The input supply should be further bypassed with a 0.01 µF - 0.1 µF ceramic capacitor, placed close to the device.
ROOT AND SELF-POWERED USB HUBS USB BUS-POWERED FUNCTIONS AND GENERAL IN-RUSH CURRENT LIMITING APPLICATIONS The LM3544 can be placed at the power-supply input of USB bus-powered functions, or other similar devices, to protect them from high in-rush currents. If the current being delivered to the device were to exceed the 2.0A over-current threshold (typ.) of the LM3544, switches in violation would open to protect the device from damage.
LM3544 Typical Applications In order to allow the power-switching circuit to smoothly transition from one supply to another, delay networks must be placed before the enable pins. These delay networks account for the turn-on delay of the LM3544 switches by slowing the fall time of the enable signals. Rise times of these signals are not affected by the delay networks.
inches (millimeters) Order Number LM3544M-H, LM3544M-L, LM3544MX-H or LM3544MX-L, NS Package Number M16A National does not assume any responsibility for use of any circuitry described, no circuit patent licenses are implied and National reserves the right at any time without notice to change said circuitry and specifications. For the most current product information visit us at www.national.com.
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