FireWire Current Limiter and Low-Drop ORing Switch Controller

The MAX5943 is a fully integrated power-management IC for FireWire® applications. This device controls two external power n-channel MOSFETs to regulate current from the input power supply to the load and performs low-voltage-drop, power-supply ORing. The MAX5943 operates over a 7.5V to 37V input range and provides inrush and output current limit in addition to a diode ORing function suitable for FireWire applications. The MAX5943 FireWire/IEEE 1394™ protective circuit (Figure 12 of the full data sheet) is UL® recognized.

The MAX5943 allows the safe insertion and removal of FireWire peripherals into a live FireWire port by providing inrush current control and an output current-limiting function. 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 both external MOSFETS, the MAX5943 provides a true bidirectional load disconnect. A low-current shutdown mode disables the MAX5943, resulting in less than 10µA supply current. A pin-selectable input allows latched or autoretry fault management after a fault.

The MAX5943A features a current-limit function that actively limits the current drawn by the load with a programmable timeout. The MAX5943B–MAX5943E do not actively limit the load current but provide a circuit-breaker function. See the Selector Guide in the full data sheet for the default and programmable circuit-breaker timeouts.

The MAX5943 operates over the -40°C to +85°C extended temperature range and is available in a 16-pin QSOP 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

* UL-Recognized FireWire/IEEE 1394 Protective Circuit

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

* Programmable Active Current Limit (MAX5943A)

* Programmable Circuit Breaker (MAX5943B–MAX5943E)

* ±5% Current-Limit Sensing Accuracy

* Programmable Current-Limit/Circuit-Breaker Timeout

* Fast Current-Limit Response to Output Short-Circuit Conditions (MAX5943A)

* Drives External n-Channel Power MOSFETs

* Overcurrent Fault Status Output

* Latched or Autoretry Overcurrent Fault Management

* 10µA Shutdown Current

* ON/OFF Control Allows Undervoltage Lockout Programming

* Fast Load Disconnect Control Through ON Input