1FEATURES
• Compatible with USB1.1 and USB 2.0
• 90mΩ (typ.) High-Side MOSFET Switch
• 500mA Continuous Current per Port
• 7 ms Fault Flag Delay Filters Hot-Plug Events
• Industry Standard Pin Order
• Short Circuit Protection with Power-Saving
Current Foldback
• Thermal Shutdown Protection
• Undervoltage Lockout
• Recognized by UL and Nemko CB
• Input Voltage Range: 2.7V to 5.5V
• 5μA Maximum Standby Supply Current
• 16-Pin SOIC Package
• Ambient Temperature Range: −40°C to 85°C

APPLICATIONS
• USB Root, Self-Powered, and Bus-Powered
Hubs fold•
USB Devices such as Monitors and Printers
• General Purpose High Side Switch
Applications

DESCRIPTION
The LM3544 is a quad high-side power switch that is
an excellent choice for use in Root, Self-Powered and
Bus- Powered 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.
The LM3544 accepts input voltages between 2.7V
and 5.5V. The Enable logic inputs, available in active-
high and active-low versions, can be powered off any
voltage in the 2.7V to 5.5V range. The LM3544 limits
the continuous current through a single port to 1.25A
max.) when it is shorted to ground.
The low on-state resistance of the LM3544 switches
ensures the LM3544 will satisfy USB voltage drop
requirements, even when current through a switch
reaches 500 mA. Thus, High-Powered USB
Functions, Low-Powered USB functions, and Bus-
Powered USB Hubs can all be powered off a Root or
Self-Powered USB Hub containing the LM3544.
Added features of the LM3544 include current fold•
back to reduce power consumption in current overload conditions, thermal shutdown to prevent
device failure caused by high current overheating,
and undervoltage lockout to keep switches from
operating if the input voltage is below acceptable
levels.