Quad Network Power Controller for Power-Over-LAN

The MAX5945 quad network power controller is designed for use in IEEE® 802.3af-compliant power-sourcing equipment (PSE). The device provides power devices (PD) discovery, classification, current-limit, and both DC and AC load disconnect detections. The MAX5945 can be used in either endpoint PSE (LAN switches/routers) or midspan PSE (power injector) applications.

The MAX5945 can operate autonomously or be controlled by software through an I²C-compatible interface. Separate input and output data lines (SDAIN and SDAOUT) allow usage with optocouplers. The MAX5945 is a slave device. Its four address inputs allow 16 unique MAX5945 addresses. A separate active-low INT output and four independent shutdown inputs (active-low SHD) allow fast response from a fault to port shutdown. An active-low RESET input allows hardware reset of the device. A special watchdog feature allows the hardware to gracefully take over control if the software crashes. A cadence timing feature allows the MAX5945 to be used in midspan systems.

The MAX5945 is fully software configurable and programmable. A class-overcurrent detection function enables system power management to detect if a PD draws more current than the allowable amount for its class. Other features are input under/overvoltage lockout, overtemperature protection, output-voltage slew-rate limit during startup, power-good, and fault status. The MAX5945's programmability includes gate-charging current, current-limit threshold, startup timeout, overcurrent timeout, autorestart duty cycle, PD disconnect AC detection threshold, and PD disconnect detection timeout.

The MAX5945 is available in a 36-pin SSOP package and is rated for both extended (-40°C to +85°C) and commercial (0°C to +70°C) temperature ranges.

Applications

* Midspan Power Injector * Power-Over-LAN/Power-Over-Ethernet * Power-Sourcing Equipment (PSE) * Switches/Routers

* IEEE 802.3af Compliant

* Controls Four Independent, -48V-Powered Ethernet Ports in Either Endpoint or Midspan PSE Applications

* Wide Digital Power Input, VDIG, Common-Mode Range: VEE to (AGND + 7.7V)

* PD Violation of Class Current Protection

* PD Detection and Classification

* Provides Both DC and AC Load Removal Detections

* I²C-Compatible, 3-Wire Serial Interface

* Fully Programmable and Configurable Operation Through I²C Interface

* Current Foldback and Duty-Cycle-Controlled/Programmable Current Limit

* Short-Circuit Protection with Fast Gate Pulldown

* Direct Fast Shutdown Control Capability

* Programmable Direct Interrupt Output

* Watchdog Mode Enable Hardware Graceful Takeover