PoE Controllers Target VoIP Apps

Eliminating external power supplies for VoIP phones, WLAN access points, and security cameras, the company's two families of Power-over-Ethernet (PoE) interface controllers are fully compliant with the IEEE 802.3af specification for powered devices. Each device consists of two sections: the IEEE802.3af-compliant interface to the PoE-powered RJ-45 wall socket and the hot-swap controller. They integrate a power MOSFET handling transients up to 100V. Hot swap features include inrush-current limiting, under-voltage lockout, and thermal-overload protection. The STHS2375, STHS2376, STHS2377, STHS4257A/L, and STHS4257A1/L1 are available with either latched operation or automatic retry after fault conditions. The STHS4257 integrates a 25-kΩ signature resistor with signature-disable function, while the STHS237x requires an external resistor. The STHS237x family also offers devices for all UVLO limit configurations: IEEE compliant (STHS2375), programmable (STHS2376), and for legacy systems (STHS2377). The STHS4257A1/L1 includes a dual-level current-limit circuit, which allows it to interface with legacy PoE systems while maintaining compatibility with the IEEE 802.3af specification. Both families are available now with prices ranging from $1.01 to $1.35 each/1,000. STMICROELECTRONICS, Lexington, MA. (888) 787-3550.