Dual Port USB Power Switch and Over-current Protection
National Semiconductor
Description
The LM3526 provides Universal Serial Bus standard power switch and over-current protection for all host port applications. The dual port device is ideal for Notebook and desktop PC's that supply power to more than one port. A 1 ms delay on the fault flag output prevents erroneous overcurrent reporting caused by in-rush currents during hot-plug events. The dual stage thermal protection circuit in the LM3526 provides individual protection to each switch and the entire device. In a short-circuit/over-current event, the switch dissipating excessive heat is turned off, allowing the second switch to continue to function uninterrupted. The LM3526 accepts an input voltage between 2.7V and 5.5V allowing use as a device-based in-rush current limiter for 3.3V USB peripherals, as well as Root and Self-Powered Hubs at 5.5V. The Enable inputs accept both 3.3V and 5.0V logic thresholds. The small size, low RON, and 1 ms fault flag delay make the LM3526 a good choice for root hubs as well as per-port power control in embedded and stand-alone hubs.
Features
Compatible with USB1.1 and USB 2.0
1 ms fault flag delay filters Hot-Plug events
Smooth turn-on eliminates in-rush induced voltage drop
UL recognized component: REF# 205202
1A nominal short circuit output current protects PC power supplies
Thermal shutdown protects device in direct short condition
500mA minimum continuous load current
Small SO-8 package minimizes board space
2.7V to 5.5V input voltage range
140 m Max. switch resistance
1 µA Max. standby current
200 µA Max. operating current
Under-voltage lockout (UVLO)
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