The MAX5992A/MAX5992B multisource, high-power, high-performance powered device (PD) controllers provide a complete interface control for PDs to comply with the IEEE® 802.3af/at standard in a Power-over-Ethernet (PoE) system. The devices provide the PD with a detection signature, classification signature, and an isolation MOSFET driver with current-limit control. In addition, the intelligent maintain power signature (MPS) and active FET bridge control make the PD more power efficient. The devices feature a active-low SIG_OK output signal for high-power Multi-2P PD applications. The selectable inrush-current modes allow Multi-PD, fiber-to-the-home/fiber-to-the-building (FTTH/FTTB) operation in redundancy applications. The devices feature an input UVLO, wide hysteresis, and long deglitch time to compensate for twisted-pair cable resistive drop to assure glitch-free transition during power-on/power-off conditions. The devices can operate from a 20.8V low-voltage supply by a selectable UVLO. The devices can withstand up to 100V at the input.
The devices support a 2-Event classification method as specified in the IEEE 802.3at standard and provide a signal to indicate when probed by Type 2 power-sourcing equipment (PSE). The devices detect the presence of a wall adapter power-source connection and allow a smooth switchover from the PoE power source to the wall power adapter. Moreover, the selectable WAD_SEL supports seamless power transition from a wall adapter to PoE if PoE is already enabled.
The devices also provide a power-good (PG) signal, 2-level current limit, foldback, and overtemperature protection. A sleep mode feature provides low-power consumption while supporting MPS. An ultra-low power sleep mode feature further reduces power consumption to comply with ultra-low power requirements while still supporting MPS. The devices also feature an LED driver that is automatically activated during sleep/ultra-low power sleep/MPS mode. The MAX5992A has 38.6V PoE UVLO and the MAX5992B has 35.4V PoE UVLO and feature a 6.5s sleep mode delay.
The MAX5992A/MAX5992B are available in a 24-pin, 4mm x 4mm, TQFN power package and are rated over the -40°C to +85°C extended temperature range.
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