LTC4257-1 IEEE 802.3af PD Power over Ethernet Interface Controller with Dual Current Limit FEATURES DESCRIPTIO Complete Power Interface Port for IEEE 802 .3af The LTC 4257-1 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 LTC4257-1 Precision Dual Level Current Limit simplifies Powered Device (PD) design by incorporating Onboard 25k Signature Resistor with Disable the 25k signature resistor, classification current source, Programmable Classification Current (Class 0-4) input current limit, undervoltage lockout, thermal over- Undervoltage Lockout load protection, signature disable and power good signal- Thermal Overload Protection ling, all in a single 8-pin package. The LTC4257-1 includes Power Good Signal a precision, dual level current limit circuit. This allows it to Available in 8-Pin SO and Low Profile (3mm 3mm) charge large load capacitors and interface with legacy DFN Packages Power over Ethernet systems while maintaining compat- ibility with the current IEEE 802.3af specification. By U incorporating a high voltage power MOSFET onboard, the APPLICATIO S LTC4257-1 provides the system designer with reduced cost while also saving board space. IP Phone Power Management Wireless Access Points The LTC4257-1 can interface directly with a variety of Lin- Telecom Power Control ear Technology DC/DC converter products to provide a cost effective power solution for IP phones, wireless access points and other PDs. Linear Technology also provides network power controllers for Power Sourcing Equipment (PSE) applications. The LTC4257-1 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 Powered Device (PD) LTC4257-1 + 5F V IN ~ + GND SMAJ58A MIN 48V FROM SWITCHING POWER SOURCING DF01SA 0.1F R SIGDISA CLASS 100k POWER SUPPLY EQUIPMENT + (PSE) PWRGD SHDN ~ 3.3V R CLASS RTN TO LOGIC V V IN OUT 42571 TA01 42571fb 1 U ULTC4257-1 ABSOLUTE AXI U RATI GS (Notes 1, 2) Operating Ambient Temperature Range V Voltage ............................................. 0.3V to 100V IN LTC4257C-1 ............................................ 0C to 70C V , SIGDISA, OUT LTC4257I-1 ......................................... 40C to 85C PWRGD Voltage ...................... V + 100V to V 0.3V IN IN Storage Temperature Range R Voltage ............................ V + 7V to V 0.3V CLASS IN IN S8 Package....................................... 65C to 150C PWRGD Current .................................................. 10mA DD Package ...................................... 65C to 125C R Current .................................................. 100mA CLASS Lead Temperature (Soldering, 10 sec).................. 300C UUW PACKAGE/ORDER I FOR ATIO TOP VIEW TOP VIEW NC 1 8 GND NC 1 8 GND R 2 7 SIGDISA R 2 7 SIGDISA CLASS CLASS NC 3 6 PWRGD NC PWRGD 3 6 V V 4 5 IN OUT V 4 5 V IN OUT S8 PACKAGE DD PACKAGE 8-LEAD PLASTIC SO 8-LEAD (3mm 3mm) PLASTIC DFN T = 150C, = 150C/W JMAX JA T = 125C, = 43C/W JMAX JA EXPOSED PAD TO BE SOLDERED TO ELECTRICALLY ISOLATED PCB HEATSINK ORDER PART NUMBER S8 PART MARKING ORDER PART NUMBER DD PART MARKING* LTC4257CS8-1 42571 LTC4257CDD-1 LBFZ LTC4257IS8-1 4257I1 LTC4257IDD-1 Order Options Tape and Reel: Add TR Lead Free: Add PBF Lead Free Tape and Reel: Add TRPBF Lead Free Part Marking: