STMicroelectronics Introduces New Power-over-Ethernet Interface Controllers for Networked Devices

STMicroelectronics announced two new families of Power-over-Ethernet (PoE) interface controllers. All devices in the families are fully compliant with the IEEE 802.3af specification for powered devices (PD), which provide all the control functions needed to enable a PD to request and draw power from an Ethernet network via a power source. By using these new controllers, designers will be able to eliminate the 110/220V AC power lines to many wired LAN devices such as VoIP (Voice over IP) phones and security cameras. Other applications benefiting from PoE include webcams, wireless LAN (WLAN) access points, point of sale (POS) terminals and RFID readers.

The STHS4257 and STHS237x PoE Powered Device Interface Controllers enable greater flexibility in installation locations, and lower overall product cost, by removing the external power supplies; the standard CAT5 Ethernet cabling can now carry power and data to devices on the network. The controllers are drop-in replacements for competitors’ products.

Each device consists of two main sections: the IEEE802.3af-compliant interface to the PoE-powered RJ–45 wall socket, which includes basic PD Detection and Classification functions; and the Hot Swap Controller (HSC), which protects the PD during insertion, operation and power withdrawal. The controllers integrate a high-voltage power MOSFET (low-side switch), with low RDS ON, and with the capability to accept transients as high as 100V. The ‘hot swap’ features include functions such as inrush current limiting, undervoltage lockout (UVLO), and thermal overload protection.