MAX5981B

The MAX5981 provides a complete interface for a powered device (PD) to comply with the IEEE® 802.3af/at standard in a power-over-ethernet (PoE) system. The MAX5981 provides the PD with a detection signature, classification signature, and an integrated isolation power switch with inrush current control. During the inrush period, the MAX5981 limits the current to less than 180mA before switching to the higher current limit (720mA to 880mA) when the isolation power MOSFET is fully enhanced. The device features an input UVLO with wide hysteresis and long deglitch time to compensate for twisted-pair cable resistive drop and to assure glitch-free transition during power-on/-off conditions. The MAX5981 can withstand up to 100V at the input.

The MAX5981 supports a 2-Event classification method as specified in the IEEE 802.3at standard and provides a signal to indicate when probed by a Type 2 power sourcing equipment (PSE). The device detects the presence of a wall adapter power source connection and allows a smooth switch over from the PoE power source to the wall power adapter.

The MAX5981 also provides a power-good (PG) signal, two-step current limit and foldback, overtemperature protection, and di/dt limit. A sleep mode feature in the MAX5981 provides low power consumption while supporting Maintain Power Signature (MPS). An ultra-low-power sleep mode feature in the MAX5981 further reduces power consumption while still supporting MPS. The MAX5981 also features an LED driver that is automatically activated during sleep mode. During sleep mode, the LED driver sources a periodic current (I_LED) at 250Hz (MAX5981A) or 15.625kHz (MAX5981B).

The MAX5981 is available in a 16-pin, 5mm x 5mm TQFN power package. The device is rated over the -40°C to +85°C extended temperature range.

Applications

• IEEE 802.3af/at Powered Devices
• IP Phones, Wireless Access Nodes, IP Security Cameras
• WiMAX™ Base Stations