LT4295
IEEE 802.3bt PD Interface
with Forward/Flyback Controller
FEATURES DESCRIPTION
n
IEEE 802.3af/at/bt Powered Device (PD) with The LT 4295 is an IEEE 802.3af/at/bt-compliant powered
Forward/Flyback Controller device (PD) interface controller with a switching regulator
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Supports Up to 71.3W PDs controller. The T2P output indicates the number of clas-
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5-Event Classification Sensing sification events received during IEEE 802.3bt-compliant
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Superior Surge Protection (100V Absolute Maximum) mutual identification and negotiation of available power.
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Wide Junction Temperature Range (40C to 125C)
The LT4295 supports both forward and flyback power
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>94% End-to-End Efficiency with LT4321 Ideal Bridge
supply topologies. The flyback topology supports No-Opto
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External Hot Swap N-Channel MOSFET for Lowest
feedback. Auxiliary input voltages can be accurately sensed
Power Dissipation and Highest System Efficiency
with just a resistor divider connected to the AUX pin.
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No-Opto Flyback Operation
n The LT4295 utilizes an external, low R N-channel
Auxiliary Power Support as Low as 9V DS(on)
n ++ hot swap MOSFET and supports the LT4320/LT4321 ideal
Easy Migration of LTPoE PDs to IEEE 802.3bt PDs
n diode bridges, to extend the end-to-end power delivery
Pin Compatible with LT4276A/B/C
n efficiency and eliminate costly heat sinks.
28-Lead 4mm 5mm QFN Package
The LT4295 also includes an on-chip detection signature
APPLICATIONS
resistor, thermal protection, slope compensation, and
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many user configurable settings including classification
High Power Wireless Data Systems
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signature, inrush current, switcher frequency, gate drive
Outdoor Security Camera Equipment
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delay, soft-start and load compensation.
Commercial and Public Information Displays
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All registered trademarks and trademarks are the property of their respective owners.
High Temperature Applications
TYPICAL APPLICATION
IEEE 802.3bt 71.3W (Class 8) PD Controller and Power Supply in Forward Mode
+
AUX
Single-Signature
37V TO 57V
Power Classification
+ + (at PD Input)
V
PORT 22F +
5V
FMMT723
CLASS POWER
13A
0.1F
100H
3.3k
0 13W
10nF BAV19WS 10F
1 3.84W
(T 50ns)
RR
VPORT HS V HS SW V FFS PG
IN CC 2 6.49W
GATE SRC VCC DLY
V
CC
+
AUX ISEN
3 13W
20m
LT4295
ISEN 4 25.5W
RCLASS
SG
++ 5 40W
RCLASS
100pF
0.1F 10k
GND FB31 SS ROSC T2P ITHB
6 51W
7 62W
100k
OPTO
TO MICROPROCESSOR
8 71.3W
4295 TA01
Rev. B
1
Document Feedback For more information www.analog.comLT4295
ABSOLUTE MAXIMUM RATINGS PIN CONFIGURATION
(Notes 1, 2)
VPORT, HSSRC, V Voltages .................. 0.3V to 100V
IN
TOP VIEW
HSGATE Current.................................................. 20mA
V Voltage .................................................. 0.3V to 8V
CC
++
RCLASS, RCLASS 28 27 26 25 24 23
GND 1 22 DNC
Voltages .............................. 0.3V to 8V (and VPORT)
AUX 2 21 V
CC
SFST, FFSDLY, ITHB, T2P Voltages ... 0.3V to V +0.3V
CC
++
RCLASS
3 20 PG
+
ISEN , ISEN Voltages ...........................................0.3V
29
RCLASS 4 19 GND
GND
FB31 Voltage ..................................................+12V/30V
T2P 5 18 SG
++
+
RCLASS/RCLASS Current .............................. 50mA
V 6 17 ISEN
CC
AUX Current ........................................................ 1.4mA V 7 16 ISEN
CC
V 8 15
RLDCMP
ROSC Current ..................................................... 100A CC
9 10 11 12 13 14
RLDCMP Current ................................................500A
T2P Current .........................................................2.5mA
Operating Junction Temperature Range (Note 3)
UFD PACKAGE
28-LEAD (4mm 5mm) PLASTIC QFN
LT4295I ................................................40C to 85C
T = 150C, = 3.4C/W
JMAX JC
LT4295H ............................................ 40C to 125C
EXPOSED PAD (PIN 29) IS GND, MUST BE SOLDERED TO PCB
Storage Temperature Range .................. 65C to 150C
ORDER INFORMATION
LEAD FREE FINISH TAPE AND REEL PART MARKING* PACKAGE DESCRIPTION TEMPERATURE RANGE
LT4295IUFD#PBF LT4295IUFD#TRPBF 4295 28-Lead (4mm 5mm) Plastic QFN 40C to 85C
LT4295HUFD#PBF LT4295HUFD#TRPBF 4295 28-Lead (4mm 5mm) Plastic QFN 40C to 125C
Contact the factory for parts specified with wider operating temperature ranges. *The temperature grade is identified by a label on the shipping container.
Tape and reel specifications. Some packages are available in 500 unit reels through designated sales channels with #TRMPBF suffix.
Rev. B
2
For more information www.analog.com
V VPORT
CC
ROSC
NC
SFST
HSGATE
FFSDLY HSSRC
ITHB V
IN
FB31 SWVCC