LTC4278
IEEE 802.3at PD with
Synchronous No-Opto Flyback
Controller and 12V Aux Support
DESCRIPTION
FEATURES
The LTC®4278 is an integrated Powered Device (PD)
controllerandswitchingregulatorintendedforhighpower
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25.5W IEEE 802.3at Compliant (Type 2) PD
10V to 57V Auxiliary Power Input
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Shutdown Pin for Flexible Auxiliary Power Support
Integrated State-of-the-Art No-Opto Synchronous
Flyback Controller
IEEE 802.3at and 802.3af applications. With a wide input
voltagerange,theLTC4278isspecificallydesignedtosup-
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
LTC4278supportsboth1-eventand2-eventclassifications
as defined by the IEEE, thereby allowing the use in a wide
range of product configurations.
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– Isolated Power Supply Efficiency >92%
– 88% Efficiency Including Diode Bridge and
Hot Swap™ FET
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Superior EMI Performance
Robust 100V 0.7Ω (Typ) Integrated Hot Swap MOSFET
IEEE 802.3at High Power Available Indicator
Integrated Signature Resistor and Programmable
Class Current
Undervoltage, Overvoltage and Thermal Protection
Short-Circuit Protection with Auto-Restart
Programmable Soft-Start and Switching Frequency
Complementary Power Good Indicators
Thermally Enhanced 7mm × 4mm DFN Package
TheLTC4278synchronous,currentmode,flybackcontrol-
ler generates multiple supply rails in a single conversion
stepprovidingforthehighestsystemefficiencywhilemain-
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.
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APPLICATIONS
The LTC4278 is available in a space saving 32-pin DFN
package.
L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks of Linear
Technology Corporation. Hot Swap is a trademark of Linear Technology Corporation.
All other trademarks are the property of their respective owners. Protected by U.S. Patents,
including 5841643.
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VoIP Phones with Advanced Display Options
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Dual-Radio Wireless Access Points
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PTZ Security Cameras
RFID Readers
Industrial Controls
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EPC3472G-LF
TYPICAL APPLICATION
25W PD Solution with 12V Auxiliary
•
0.18μH
47μF
5V
5A
2.2μH
+
+
•
+
100μF
AUXILIARY
•
10μF
10μF
100k
SUPPLY
(10V TO 57V)
–
294k
21.5k
3.01k
BSS63LT1
1μF
680k
TO MICRO
CONTROLLER
HAT2169
41.2k
FDMS2572
12mΩ
~ +
~ –
54V FROM
DATA PAIR
PDS5100H
+
–
FB
V
PG SENSE
UVLO PWRGD T2P
PORTP
SHDN
CC
V
SENSE
R
CLASS
LTC4278
0.1μF
24k
30.9ꢀ
~ +
~ –
SG
CMP
54V FROM
SPARE PAIR
2.2nF
V
V
1μF
PORTN
NEG
V
SYNC GND OSC PGDLY
10k
t
ENDLY
100k
R
C
CMP
ON
CMP
•
•
38.3k 1.8k
33pF
0.1μF
4278 TA01a
4278f
1