TPS2371

TPS2371 SLUS566A − JULY 2003 − REVISED NOVEMBER 2003 LEGACY/IEEE802.3af COMPATIBLE POWER INTERFACE SWITCH FOR POWER OVER ETHERNET (PoE) POWERED DEVICES FEATURES D Integrated Power Interface Switch for IEEE 802.3af Powered Devices (PDs) D Precision UVLO Thresholds D 20-ms UVLO Off-Time Delay D Provides PD Detection Signature D Provides PD Classification Signature (Class 0−4) D Programmable Inrush Current Limit D Internal 0.3-Ω Low-Side FET D Interfaces to DC/DC Soft-Start for DC/DC Enable D Internal Thermal Protection – Disconnects PD Load D 8-Pin SOIC, 8-Pin TSSOP Packages APPLICATIONS D VoIP Phones D Internet Appliances D Wireless LAN Access Points D Bluetooth Access Points DESCRIPTION Acting as an interface between the Power Source Equipment (PSE) and the Powered Device (PD), the TPS2371 performs all detection, class− ification, inrush current limiting, and switch FET control that is necessary for compatibility with Legacy/IEEE 802.3af Standard. The TPS2371 incorporates precision UVLO thresholds and hysteresis as well as a UVLO off-time delay to enable Legacy IEEE802.3af PoE compatibilty. An internal 0.3-Ω FET provides maximum power delivery. As an additional feature, the TPS2371 interfaces with the enable/soft-start signal of a dc-to-dc converter, eliminating the need to have an accurate UVLO in the dc-to-dc converter. At low input voltages (1.8 V to 10 V), the TPS2371 draws less than 12 µA, allowing accurate sensing of the external 24.9-kΩ discovery resistor. At input...