Dual FireWire Current Limiter and Low-Drop ORing Switch Controller

The MAX5944 is a dual, current limiter/low-drop ORing, switch controller power-management IC for FireWire® applications. Each independent channel controls two external power MOSFETs to regulate current from the input power supply to the load and performs low-voltagedrop power-supply ORing. The MAX5944 operates over the 7.5V to 37V input range and provides inrush and output current limit in addition to diode ORing functions suitable for FireWire applications.

The MAX5944 allows the safe insertion and removal of FireWire peripherals into a live FireWire port by providing inrush current control and output current-limiting functions. The MAX5944 features a current-limit function that actively limits the current drawn by the load with a 2ms timeout. Its autoretry function then automatically restarts after the 259ms autoretry delay time.

The ORing feature provides a very efficient way to protect the FireWire port when connected to another FireWire peripheral that sources a higher voltage. By turning off the external MOSFETS, the MAX5944 provides a true bidirectional load disconnect. Each channel has an independent ON/OFF control that results in less than 10µA supply current per channel.

The MAX5944 operates over the -40°C to +125°C extended temperature range and is available in a 16-pin SO package.

Applications

* FireWire® Desktop/Notebook Port * FireWire® Hub * FireWire® Peripheral Device Current Limit * Hot Swap

* Provides Safe Hot-Swap for 7.5V to 37V Power Supplies

* Dual-Channel Hot-Swap

* Low-Drop Power ORing with Ultra-Fast Turn-Off

* Active Current Limit

* ±5% Current-Limit Sensing Accuracy

* 2ms Current-Limit Timeout

* Fast Current-Limit Response to Output Short-Circuit Conditions

* Drives External n-Channel Power MOSFETs

* Independent Overcurrent Fault Status Outputs

* 259ms Autoretry Period

* 10µA (Per Channel) Shutdown Current

* Independent ON/OFF Control Allows Undervoltage Lockout Programming

* Fast Load Disconnect Control Through ON/OFF Inputs

* Bidirectional Load Disconnect

* Power Routing from One Port to Another