LT4321 PoE Ideal Diode Bridge Controller Fea T Descrip T n Reduces Heat, Eliminates Thermal Design Problems The LT 4321 is a dual ideal diode bridge controller that n Maximizes Power Efficiency enables a Power over Ethernet (PoE) powered device n Less than 800A Quiescent Operating Current (PD) to receive power in either voltage polarity from n Fully Compatible with IEEE 802.3 Detection and RJ-45 data pairs, spare pairs, or both. The LT4321 and Classification eight N-channel MOSFETs replace the eight diodes in a n IEEE 802.3 Compliant When Paired with a Powered passive PoE rectifier bridge. The LT4321 eases thermal Device (PD) Controller design and increases delivered power. n Works with 2-Pair and 4-Pair PoE Applications An internal charge pump allows an all-NMOS bridge n + ++ Compatible with PoE, PoE , and LTPoE eliminating larger and more costly PMOS switches. The n 100V Absolute Maximum Voltage LT4321 works with 2-pair and 4-pair applications. High n H-Grade Version Operates Up to 125C impedance input sense pins prevent reverse current on n 16-Lead 4mm 4mm QFN Package unused pairs. If the power source fails or is shorted, a fast turn-off minimizes reverse current transients. Unlike a T discrete ideal bridge solutions, the LT4321 will operate through transients without enabling the MOSFETs on n + ++ PoE/PoE / LTPoE Powered Devices unpowered pairs. n DC Polarity Correction and Ideal Diode-ORing of L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks and Telecom Supplies ++ PowerPath and LTPoE are trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners. Typical a T + ++ Powered Device for PoE (to 13W), PoE (to 25.5W), or Linear LTPoE (to 90W) Systems 1 + 0.1F SMAJ60A 10F 2 TG12 BG12 BG36 TG36 VPORT HSGATE HSSRC DATA PAIRS 3 OUTP EN IN12 LT4275 V IN 6 IN36 LT4321 + IN45 EN ISOLATED PWRGD GND POWER V 4 OUT SUPPLY IN78 OUTN RUN 5 SPARE GND 4321 TA01 PAIRS BG45 TG45 TG78 BG78 7 8 4321f 1 For more information www.linear.com/LT4321 ion pplica ions pplica ion uresLT4321 a Te Maxi Mu M r a T p c F T (Notes 1, 2) OUTP-OUTN ............................................. 0.3V to 100V TOP VIEW IN12, IN36, IN45, IN78 ....................... 2V to OUTP + 2V BG12, BG36, BG45, BG78 Voltages .......... 0.3V to 100V 16 15 14 13 TG12, TG36, TG45, TG78 TG36 1 12 OUTP Voltages ....................................... 0.3V to OUTP + 12V IN36 2 11 EN 17 TG12-IN12 Voltage ......................................0.3V to 12V OUTN IN45 3 10 EN TG36-IN36 Voltage .....................................0.3V to 12V TG45 OUTN 4 9 TG45-IN45 Voltage .....................................0.3V to 12V 5 6 7 8 TG78-IN78 Voltage ......................................0.3V to 12V EN, EN, ..................................................... 0.3V to 100V UF PACKAGE Operating Ambient Temperature Range 16-LEAD (4mm 4mm) PLASTIC QFN T = 125C, = 4.5C/W JMAX JC LT4321I ................................................40C to 85C EXPOSED PAD (PIN 17) IS OUTN, MUST BE SOLDERED TO PCB LT4321H ............................................. 40C to 125C Storage Temperature Range .................. 65C to 150C o r D i n F Ma T LEAD FREE FINISH TAPE AND REEL PART MARKING* PACKAGE DESCRIPTION TEMPERATURE RANGE LT4321IUF PBF LT4321IUF TRPBF 4321 16-Lead 4mm 4mm Plastic QFN 40C to 85C LT4321HUF PBF LT4321HUF TRPBF 4321 16-Lead 4mm 4mm Plastic QFN 40C to 125C Consult LTC Marketing for parts specified with wider operating temperature ranges. *The temperature grade is identified by a label on the shipping container. Consult LTC Marketing for information on nonstandard lead based finish parts. For more information on lead free part marking, go to: