LTC4257 IEEE 802.3af PD Power over Ethernet Interface Controller FEATURES DESCRIPTIO Complete Power Interface Port for IEEE 802.3af The LTC 4257 provides complete signature and power Powered Devices (PDs) interface functions for a device operating in an IEEE Onboard 100V, 400mA Power MOSFET 802.3af Power over Ethernet (PoE) system. The LTC4257 Precision Input Current Limit simplifies Powered Device (PD) design by incorporating Onboard 25k Signature Resistor the 25k signature resistor, the classification current source, Programmable Classification Current (Class 0-4) input current limit with thermal foldback, undervoltage Undervoltage Lockout lockout and power good signalling, all in a single 8-pin Smart Thermal Protection package. By incorporating a high voltage power MOSFET Power Good Signal onboard, the LTC4257 provides the system designer with Available in 8-Pin SO and Low Profile (3mm 3mm) reduced cost while also saving board space. DFN Packages The LTC4257 can interface directly with a variety of Linear Technology DC/DC converter products to provide a cost U effective power solution for IP phones, wireless access APPLICATIO S points and other PDs. Linear Technology also provides IP Phone Power Management solutions for Power Sourcing Equipment (PSE) applica- Wireless Access Points tions with quad network power controllers. Telecom Power Control The LTC4257 is available in the 8-pin SO and low profile (3mm 3mm) DFN packages. , LTC and LT are registered trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners. TYPICAL APPLICATIO LTC4257 Charging 300F Load Capacitor Powered Device (PD) V IN 50V/DIV LTC4257 V V OUT IN GND ~ + SMAJ58A 20V/DIV 48V FROM + SWITCHING 5F POWER SOURCING R CLASS 0.1F 100k DF01SA POWER SUPPLY MIN EQUIPMENT + (PSE) PWRGD SHDN I IN 3.3V ~ R CLASS RTN 200mA/DIV TO LOGIC V V IN OUT 4257 TA01 PWRGD 50V/DIV 5ms/DIV 4225 TA02 4257fb 1 U ULTC4257 ABSOLUTE AXI U RATI GS (Notes 1, 2) Operating Ambient Temperature Range V Voltage ............................................. 0.3V to 100V IN LTC4257C ............................................... 0C to 70C V , PWRGD Voltage ............. V + 100V to V 0.3V OUT IN IN LTC4257I............................................. 40C to 85C R Voltage ............................ V + 7V to V 0.3V CLASS IN IN Storage Temperature Range PWRGD Current .................................................. 10mA S8 Package....................................... 65C to 150C R Current .................................................. 100mA CLASS DD Package ...................................... 65C to 125C Lead Temperature (Soldering, 10 sec).................. 300C UUW PACKAGE/ORDER I FOR ATIO TOP VIEW TOP VIEW NC 1 8 GND R 2 7 NC NC 1 8 GND CLASS NC 3 6 PWRGD R 2 7 NC CLASS V 4 5 V IN OUT NC 3 6 PWRGD V 4 5 V IN OUT DD PACKAGE 8-LEAD (3mm 3mm) PLASTIC DFN S8 PACKAGE 8-LEAD PLASTIC SO T = 125C, = 43C/W JMAX JA T = 150C, = 150C/W EXPOSED PAD TO BE SOLDERED TO JMAX JA ELECTRICALLY ISOLATED PCB HEATSINK ORDER PART NUMBER S8 PART MARKING ORDER PART NUMBER DD PART MARKING* LTC4257CS8 4257 LTC4257CDD LACT LTC4257IS8 4257I LTC4257IDD Order Options Tape and Reel: Add TR Lead Free: Add PBF Lead Free Tape and Reel: Add TRPBF Lead Free Part Marking: