LTC4258

Features:

`Controls Four Independent 48V Powered Ethernet Ports
`Each Port Includes:
  IEEE 802®.3af Compliant PD Detection and
`Classification
  Output Current Limit with Foldback
  Short-Circuit Protection with Fast Gate Pull-Down
  PD Disconnect Using DC Sensing
  Power Good Indication
`Operates Autonomously or Controlled by I²C^TM Serial Interface
`4-Bit Programmable Digital Address Allows Control of Up to 64 Ports
`Programmable INT Pin Eliminates Software Polling
`Current and Duty Cycle Limits Protect External FETs


Application

·IEEE 802.3af Compliant Endpoint and Midspan Power Sources
·IP Phone Systems
·DTE Power Distribution

Specifications

Supply Voltages
V_DD to DGND ..................................................... 0.3V to 5V
V_EE to AGND ..................................................... 0.3V to 70V
DGND to AGND (Note 2) .................................................. ±1V
Digital Pins
SCL, SDAIN, SDAOUT, INT , AUTO, RESET
SHDN n , AD n .............................. DGND 0.3V to DGND + 5V
Analog Pins
GATE n (Note 3) ............................... VEE 0.3V to VEE + 12V
DETECT n...................................... DGND 20V to DGND +0.3V
SENSE n ............................................. V_EE 0.3V to V_EE + 1V
OUT n ................................................ V_EE 70V to V_EE + 70V
OSCIN ........................................... DGND 0.3V to DGND + 5V
BYP Current .................................................................. ±0.1mA
Operating Ambient Temperature Range ................... 0 to 70
Junction Temperature (Note 5) ......................................... 150
Storage Temperature Range ............................ 65 to 150
Lead Temperature (Soldering, 10 sec)............................... 300


Description

The LTC4258 is a quad 48V Hot Swap^TM controller designed for use in IEEE 802.3af compliant Power Sourcing Equipment (PSE). It consists of four independent ports, each with output current limit, short-circuit protection, complete Powered Device (PD) detection and classification capability, and programmable PD disconnect using AC or DC sensing. Used with power MOSFETs and passives as in Figure 1, the LTC4258 can implement a complete IEEE 802.3af-compliant PSE.

The LTC4258 can operate autonomously or be controlled by an I²C serial interface. Up to 16 LTC4258s may coexist on the same data bus, allowing up to 64 powered Ethernet ports to be controlled with only two digital lines. Fault conditions are optionally signaled with the INT pin to eliminate software polling.

External power MOSFETs, current sense resistors and diodes of LTC4258 allow easy scaling of current and power dissipation levels and provide protection against voltage and current spikes and ESD events.

The LTC4258 is available in a 36-pin SSOP package.

Linear Technology also provides solutions for 802.3af PD applications with the LTC4257 and LTC4257-1.