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Linear Technology Electronic Components Datasheet

LTC4278 Datasheet

IEEE 802.3at PD

No Preview Available !

LTC4278
FEATURES
IEEE 802.3at PD with
Synchronous No-Opto Flyback
Controller and 12V Aux Support
DESCRIPTION
n 25.5W IEEE 802.3at Compliant (Type 2) PD
n 10V to 57V Auxiliary Power Input
n Shutdown Pin for Flexible Auxiliary Power Support
n Integrated State-of-the-Art No-Opto Synchronous
Flyback Controller
– Isolated Power Supply Efficiency >92%
– 88% Efficiency Including Diode Bridge and
Hot Swap™ FET
n Superior EMI Performance
n Robust 100V 0.7Ω (Typ) Integrated Hot Swap MOSFET
n IEEE 802.3at High Power Available Indicator
n Integrated Signature Resistor and Programmable
Class Current
n Undervoltage, Overvoltage and Thermal Protection
n Short-Circuit Protection with Auto-Restart
n Programmable Soft-Start and Switching Frequency
n Complementary Power Good Indicators
n Thermally Enhanced 7mm × 4mm DFN Package
APPLICATIONS
n VoIP Phones with Advanced Display Options
n Dual-Radio Wireless Access Points
n PTZ Security Cameras
n RFID Readers
n Industrial Controls
The LTC®4278 is an integrated Powered Device (PD) con-
troller and switching regulator intended for high power
IEEE 802.3at and 802.3af applications. With a wide input
voltage range, the LTC4278 is specifically designed to sup-
port PD applications that include a low-voltage auxiliary
power input such as a 12V wall adaptor. The inclusion of
a shutdown pin provides simple implementation of both
PoE and auxiliary dominate applications. In addition, the
LTC4278 supports both 1-event and 2-event classifications
as defined by the IEEE, thereby allowing the use in a wide
range of product configurations.
The LTC4278 synchronous, current mode, flyback control-
ler generates multiple supply rails in a single conversion
step providing for the highest system efficiency while main-
taining tight regulation across all outputs. The LTC4278
includes Linear Technology’s patented No-Opto feedback
topology to provide full IEEE 802.3 isolation without the
need of an opto-isolator circuit. A true soft-start function
allows graceful ramp-up of all output voltages.
The LTC4278 is available in a space saving 32-lead DFN
package.
L, LT, LTC, LTM, Linear Technology, SwitcherCAD and the Linear logo are registered
trademarks and Hot Swap and ThinSOT are trademarks of Linear Technology Corporation.
All other trademarks are the property of their respective owners. Protected by U.S. Patents,
including 5841643.
TYPICAL APPLICATION
25W PD Solution with 12V Auxiliary
+
AUXILIARY
SUPPLY
(10V TO 57V)
54V FROM
DATA PAIR
~+
~–
54V FROM
SPARE PAIR
~+
~–
PDS5100H
0.1µF
BSS63
+
10µF
294k
8.2µH
10µF
21.5k
46.4k
TO MICRO
CONTROLLER
3.01k
1µF
UVLO PWRGD T2P
VPORTP
FB VCC PG SENSE+
SHDN
RCLASS
24k 30.9Ω
VPORTN
LTC4278
SENSE
SG
VCMP
VNEG SYNC GND OSC PGDLY tON ENDLY RCMP CCMP
B1100
12k
33pF
100k 38.3k 1.8k
0.1µF
EPC3472G-LF
••
0.18µH
47µF +
5V
4.5A
100µF
FDMS2572
12mΩ
HAT2169
1µF 2.2nF
••
4278 TA01a
4278fc
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Linear Technology Electronic Components Datasheet

LTC4278 Datasheet

IEEE 802.3at PD

No Preview Available !

LTC4278
ABSOLUTE MAXIMUM RATINGS
(Notes 1, 2)
Pins with Respect to VPORTN
VPORTP Voltage.......................................... –0.3V to 100V
VNEG Voltage.......................................... –0.3V to VPORTP
VNEG Pull-Up Current...................................................1A
SHDN........................................................ –0.3V to 100V
RCLASS, Voltage............................................. –0.3V to 7V
RCLASS Source Current............................................50mA
PWRGD Voltage (Note 3)
Low Impedance Source.......VNEG –0.3V to VNEG +11V
Sink Current..........................................................5mA
PWRGD, T2P Voltage................................ –0.3V to 100V
PWRGD, T2P Sink Current......................................10mA
Pins with Respect to GND
VSCECNSVEolt,aSgeE.N...S..E..+..V...o..l.t.a.g..e....................................................–..0–.50V.3Vtoto+02.25VV
UVLO, SYNC Voltage....................................–0.3V to VCC
FB Current...............................................................±2mA
VCMP Current..........................................................±1mA
Operating Ambient Temperature Range
LTC4278C................................................. 0°C to 70°C
LTC4278I..............................................–40°C to 85°C
PIN CONFIGURATION
TOP VIEW
SHDN 1
T2P 2
32 VPORTP
31 NC
RCLASS 3
NC 4
30 PWRGD
29 PWRGD
VPORTN
VPORTN
NC
NC
5
6
7
8
28 NC
27 VNEG
26 VNEG
33 25 NC
SG 9
24 PG
VCC 10
tON 11
ENDLY 12
SYNC 13
SFST 14
23 PGDLY
22 RCMP
21 CCMP
20 SENSE+
19 SENSE
OSC 15
18 UVLO
FB 16
17 VCMP
DKD32 PACKAGE
32-LEAD (7mm × 4mm) PLASTIC DFN
TJMAX = 125°C, θJA = 34°C/W, θJC = 2°C/W
GND, EXPOSED PAD (PIN 33) MUST BE SOLDERED TO A
HEAT SINKING PLANE THAT IS CONNECTED TO VNEG
ORDER INFORMATION
LEAD FREE FINISH
TAPE AND REEL
PART MARKING*
PACKAGE DESCRIPTION
TEMPERATURE RANGE
LTC4278CDKD#PBF
LTC4278CDKD#TRPBF 4278
32-Lead (7mm × 4mm) Plastic DFN
0°C to 70°C
LTC4278IDKD#PBF
LTC4278IDKD#TRPBF 4278
32-Lead (7mm × 4mm) Plastic DFN
–40°C to 85°C
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 non-standard lead based finish parts.
For more information on lead free part marking, go to: http://www.linear.com/leadfree/
For more information on tape and reel specifications, go to: http://www.linear.com/tapeandreel/
4278fc
2


Part Number LTC4278
Description IEEE 802.3at PD
Maker Linear Technology
PDF Download

LTC4278 Datasheet PDF






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