Network Power Controller Ensures Safe Insertion Of IP Phones

Aug. 20, 2001
Hoping to get an edge in upcoming IP phones and DTE power-distribution systems, Linear Technology Corp. has readied a −48-V network power controller. The LT4255 quad controller enables the safe insertion and removal of IP phones into and from...

Hoping to get an edge in upcoming IP phones and DTE power-distribution systems, Linear Technology Corp. has readied a −48-V network power controller. The LT4255 quad controller enables the safe insertion and removal of IP phones into and from the Ethernet.

One unit can control 48 V to four IP phone lines. Each line is turned on and off via software control. The LT4255 also provides short-circuit protection, open-circuit detection, and "power good" indication for each line. To cut power dissipation in the switch during shorts and startup, current foldback is included.

External switches and current-sense resistors permit scaling of current, voltage, and power-dissipation levels. They protect against voltage and current spikes as well. Also, the LT4255 controls external n-channel MOSFETs in the −48-V power path and limits inrush current.

Other features include four independent relay drivers and a two-wire serial interface. Using a 5-bit programmable digital address, this interface lets designers control up to 128 channels via two digital lines. To avoid continuous software polling for fault detection, the controller uses a fault output signal to generate an interrupt condition.

The LT4255 is designed to comply with IEEE 802.3af. This standard, now a working draft, is expected to be adopted early next year. Implemented in biCMOS, the LT4255 will go into production next month. It's housed in a 28-pin SSOP plastic package and screened to both commercial and industrial temperature ranges. Contact Linear for pricing information.

Linear Technology Corp., 1630 McCarthy Blvd., Milpitas, CA 95035-7417; (408) 432-1900; fax (408) 434-6441; www.linear-tech.com.

Sponsored Recommendations

Comments

To join the conversation, and become an exclusive member of Electronic Design, create an account today!