MAX5969A, MAX5969B应用电路

MAX5969A, MAX5969B应用电路

Typical Application Circuit

TheMAX5969A/MAX5969Bprovide a completeinterface fora powered device (PD) to comply with the IEEE® 802.3af/at standard in a power-over-Ethernet(PoE) system. The MAX5969A/MAX5969B provide the PD with a detection signature, classification signature, and an integrated isolation power switch with inrush current control. During the inrush period, the MAX5969A/MAX5969B limit the current to less than 180mA before switching to the higher current limit (720mA to 880mA) when the isolation powerMOSFETis fully enhanced. The devices feature 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 MAX5969A/MAX5969Bcanwithstand up to 100V at the input.

The MAX5969A/MAX5969B 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 walladapter power-source connection and allow a smooth switchover from the PoE power source to the wall power adapter.

The MAX5969A/MAX5969B also provide a power-good (PG) signal, two-step current limit and foldback, overtemperature protection, and di/dt limit.

The MAX5969A/MAX5969B are available in a space-saving, 10-pin, 3mm × 3mm, TDFN power package. These devices are rated over the -40°C to +85°C extended temperature range.