LTC4265 LINER [Linear Technology], LTC4265 Datasheet
LTC4265
Available stocks
Related parts for LTC4265
LTC4265 Summary of contents
Page 1
... Interface controller intended for IEEE 802.3at high power Power-over-Ethernet (PoE) applications up to 25.5W. By supporting 1-event and 2-event classifi cation signaling as defi ned by IEEE 802.3, the LTC4265 can be used in a wide range of product confi gurations. A 100V MOSFET isolates the DC/DC converter during detection and classifi cation, and provides 100mA inrush current for a smooth power- up transition ...
Page 2
... OUT Pull-Up Current ....................................................5mA PWRGD, T2PSE Voltage ........................... –0.3V to 100V PWRGD, T2PSE Pull-Up Current ............................10mA Junction Temperature ........................................... 125°C Operating Ambient Temperature Range LTC4265C ................................................ 0°C to 70°C LTC4265I.............................................. –40°C to 85°C ORDER INFORMATION LEAD FREE FINISH TAPE AND REEL LTC4265CDE#PBF LTC4265CDE#TRPBF ...
Page 3
... Note 3: Pins with 100V absolute maximum guaranteed for T ≥ 0ºC, otherwise 90V. Note 4: PWRGD voltage clamps at 14V with respect to V Note 5: Input voltage specifi cations are defi ned with respect to LTC4265 pins and meet IEEE 802.3af/at specifi cations when the input diode bridge is included ...
Page 4
... GND VOLTAGE (V) 4265 G01 Signature Resistance vs Input Voltage – V1 RESISTANCE = = I I – DIODES: HD01 T = 25°C A IEEE UPPER LIMIT 26 LTC4265 + 2 DIODES 25 24 LTC4265 ONLY IEEE LOWER LIMIT GND VOLTAGE (V) 4265 G04 ...
Page 5
... PIN FUNCTIONS SHDN (Pin 1): Shutdown Input. Use this pin for auxiliary power application. Drive SHDN high to disable LTC4265 operation and corrupt the signature resistance. If unused, tie SHDN T2PSE (Pin 2): Type-2 PSE Indicator, Open-Drain. Low impedance indicates the presence of a Type-2 PSE. ...
Page 6
... In particular, the LTC4265 provides the T2PSE indicator bit which recognizes 2-event classifi cation. This indicator bit may be used to alert the LTC4265 output load that a Type-2 PSE is present. With an internal signature resistor, classifi cation circuitry, inrush control, and ther- ...
Page 7
... Figure 2. PD Front End Using Diode Bridges on Main and Spare Inputs The input diode bridge introduces a voltage drop that affects the range for each mode of operation. The LTC4265 compensates for these voltage drops so that a PD built with the LTC4265 meets the IEEE 802.3af/at-established voltage ranges. Note that the Electrical Specifi ...
Page 8
... IEEE 802.3af/at specifi cation, and alerts the PSE not to apply power. Invoking the SHDN pin also ceases operation for classifi cation and disconnects the LTC4265 load from the PD input. If this feature is not used, connect SHDN ...
Page 9
... The 1st classifi cation event occurs when the PSE presents an input voltage between 14.5V to 20.5V and the LTC4265 presents a class 4 load current. The PSE then drops the input voltage into the mark volt- age range of 6.9V to 10V, signaling the 1st mark event. ...
Page 10
... INRUSH CURRENT Once the PSE detects and optionally classifi es the PD, the PSE then applies powers on the PD. When the LTC4265 input voltage rises above the ON voltage threshold, LTC4265 connects ...
Page 11
... APPLICATIONS INFORMATION Once C1 is fully charged, the LTC4265 turns on is internal MOSFET and passes power to the PD load. The LTC4265 continues to power the PD load as long as the input volt- age does not fall below the UVLO threshold. When the LTC4265 input voltage falls below the UVLO threshold, the PD load is disconnected, and classifi ...
Page 12
... APPLICATIONS INFORMATION OVERVOLTAGE LOCKOUT The LTC4265 includes an overvoltage lockout (OVLO) feature (Figure 5) which protects the LTC4265 and its load from an overvoltage event. If the input voltage exceeds the OVLO threshold, the LTC4265 discontinues PD operation. Normal operations resume when the input voltage falls below the OVLO threshold and when C1 is charged up ...
Page 13
... Figure 2 shows how two diode bridges are typically con- nected application. One bridge is dedicated to the data pair while the other bridge is dedicated to the spare pair. The LTC4265 supports the use of either silicon or Schottky input diode bridges. However, there are tradeoffs in the choice of diode bridges. ...
Page 14
... However, the pins that interface to the outside world can routinely see excessive peak voltages. To protect the LTC4265, install a transient voltage suppressor (D3) be- tween the input diode bridge and the LTC4265 as shown in Figure 7. Classifi cation Resistor (R ) ...
Page 15
... T2PSE pin, and the choice of V the PoE supply rail (which the LTC4265 GND is tied to), or from the voltage source that supplies power to the DC/DC converter. Option 1 has the advantage of not drawing power unless T2PSE is declared active ...
Page 16
... In some applications desirable to power the PD from an auxiliary power source such as a wall adapter. Auxiliary power can be injected into an LTC4265-based PD at the input of the LTC4265, the output of the LTC4265, or even the output of the DC/DC converter. In addition, some PD application may desire auxiliary supply dominance or may be confi ...
Page 17
... Connect the LTC4265 exposed pad board heat sink. Make the heat sink as large as possible. Place the input capacitor and transient voltage suppres- sor (C14 and D3 in Figure 7) as close to the LTC4265 as possible. If using the SHDN pin for auxiliary power application, ...
Page 18
... LTC4265 APPLICATIONS INFORMATION 18 (V) OUTPUT (%) EFFICIENCY 4265f ...
Page 19
... DE/UE Package 12-Lead Plastic DFN (4mm × 3mm) (Reference LTC DWG # 05-08-1695 Rev C) 0.70 0.05 3.30 0.05 PACKAGE OUTLINE 0.50 BSC 2.50 REF 4.00 0.10 (2 SIDES 0.05 TYP 3.00 0.10 (2 SIDES) 0.75 0.05 BOTTOM VIEW—EXPOSED PAD 0.00 – 0.05 LTC4265 0.40 0. 0.115 TYP 7 12 3.30 0.10 1.70 0.10 PIN 1 NOTCH R = 0.20 OR 0.35 45 CHAMFER 6 1 (UE12/DE12) DFN 0806 REV D 0.25 0.05 0.50 BSC 2.50 REF ...
Page 20
... LTC4265 TYPICAL APPLICATION PoE-Based Self-Driven Synchronous Forward Power Supply GND 10μH + 2.2μF 10μF B1100 8 PLCS 100V 100V –54V FROM DATA PAIR –54V LTC4265 FROM GND SPARE SMAJ58A PAIR R CLASS 30.9Ω 0.1μF SHDN 100V OUT T2PSE Effi ciency vs Load Current 95 90 ...