LTC4268-1
High Power PD With
Synchronous No-Opto
Flyback Controller
Fea T Descrip T
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Robust 35W PD Front End
The LTC 4268-1 is an integrated Powered Device (PD)
n
IEEE 802.3af Compliant
controller and switching regulator intended for IEEE 802.3af
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Rugged 750mA Power MOSFET With Precision Dual
and high power PoE applications up to 35W. By including
Level Current Limit
a precision dual current limit, the LTC4268-1 keeps inrush
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High Performance Synchronous Flyback Controller
below IEEE 802.3af current limit levels to ensure interop-
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IEEE Isolation Obtained Without an Opto-Isolator
erability success while enabling high power applications
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Adjustable Frequency from 50kHz to 250kHz
with a 750mA operational current limit.
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Tight Multi-Output Regulation With Load
The LTC4268-1 synchronous, current-mode, flyback
Compensation
controller generates multiple supply rails in a single
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Onboard 25k Signature Resistor
conversion providing for the highest system efficiency
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Programmable Classification Current to 75mA
while maintaining tight regulation across all outputs. The
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Complete Thermal and Over-Current Protection
LTC4268-1 includes Linear Technologys patented No-Opto
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Available in Compact 32-Pin 7mm 4mm DFN
feedback topology to provide full IEEE 802.3af isolation
Package
without the need of opto-isolator circuitry.
a T The oversized power path and high performance flyback
controller of the LTC4268-1 combine to make the ultimate
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VoIP Phones With Advanced Display Options
solution for power hungry PoE applications such as WAPs,
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Dual-Radio Wireless Access Points
PTZ security cameras, RFID readers and ultra-efficient
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PTZ Security Cameras
802.3af applications running near the 12.95W limit.
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RFID Readers
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The LTC4268-1 is available in a space saving 32-pin DFN
Industrial Controls
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package.
Magnetic Card Readers
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High Power PoE Systems
L, LT, LTC, LTM and SwitcherCAD are registered trademarks and LTPoE++ 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 a T
35W High Efficiency PD Solution
3.3V
+
470F
5F 100pF
4
BAS21 28.7k T1
47k
1% 47
T1
56
SMAJ58A 20
100k
B0540W
DF1501S 3.01k
FMMT618
1%
47F
~ + Si4490DY Si7336ADP
54V FROM
DATA PAIR
~
FMMT718
+
0.1F
V PWRGD PWRGD UVLO I V FB PG
SENSE
PORTP LIM_EN CC
DF1501S
1F
0.02
SHDN
~ +
54V FROM
SPARE PAIR
~ SENSE
15
LTC4268-1
330
R
CLASS
SG
0.1F 2.2nF
V
CMP
T2
V V PGDLY t SYNC R ENDLY OSC GND SFST C
PORTN NEG ON CMP CMP
10nF
R 12k 169k 100k 10k
CLASS BAT54
T1: PA1477NL
20k
47pF
T2: PA0184
42681 TA01a
0.033F
42681fc
1
+
ion pplica
ions pplica
ion uresLTC4268-1
a Te Maxi Mu M r a T p c F T
(Notes 1, 2)
TOP VIEW
V Voltage .......................................... 0.3V to 90V
PORTN
SHDN 1 32 V
PORTP
V Voltage ..................V + 90V to V 0.3V
NEG PORTN PORTN
NC 2 31 NC
V to GND Voltage (Note 3)
CC
R 3 30 PWRGD
CLASS
Low Impedance Source ......................... 0.3V to 18V
I 4 29 PWRGD
LIM_EN
Current Fed ..........................................30mA into V
CC
V 5 28 V
PORTN NEG
R , I Voltage ..V + 7V to V 0.3V
CLASS LIM_EN PORTN PORTN
V 6 27 V
PORTN NEG
SHDN Voltage ...............V + 90V to V 0.3V
PORTN PORTN
V 7 26 V
PORTN NEG
PWRGD Voltage (Note 3)
NC 8 25 NC
33
Low Impedance Source .... V + 11V to V 0.3V
NEG NEG
SG 9 24 PG
Current Fed ..........................................................5mA
V 10 23 PGDLY
CC
PWRGD Voltage ............V + 80V to V 0.3V
t 11 22 R
PORTN PORTN ON CMP
PWRGD Current .....................................................10mA ENDLY 12 21 C
CMP
SYNC 13 20 SENSE+
R Current ....................................................100mA
CLASS
+
SFST 14 19 SENSE
SENSE , SENSE Voltage ........................ 0.5V to +0.5V
OSC 15 18 UVLO
UVLO, SYNC Voltage ...................................0.3V to V
CC
FB 16 17 V
CMP
FB Current ..............................................................2mA
V Current ......................................................... 1mA
CMP
DKD32 PACKAGE
32-LEAD (7mm 4mm) PLASTIC DFN
Operating Ambient Temperature Range (Notes 4, 5)
T = 150C, = 49C/W, = 4.7C/W
JMAX JA JC
LTC4268-1C ............................................. 0C to 70C
EXPOSED PAD (PIN 33) MUST BE SOLDERED TO
HEAT SINKING PLANE THAT IS ELECTRICALLY CONNECTED TO GND
LTC4268-1I ..........................................40C to 85C
Junction Temperature (Note 5) ............................. 150C
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
LTC4268CDKD-1#PBF LTC4268CDKD-1#TRPBF 42681 32-Lead (7mm 4mm) Plastic DFN 0C to 70C
LTC4268IDKD-1#PBF LTC4268IDKD-1#TRPBF 42681 32-Lead (7mm 4mm) Plastic DFN 40C to 85C
LEAD BASED FINISH TAPE AND REEL PART MARKING* PACKAGE DESCRIPTION TEMPERATURE RANGE
LTC4268CDKD-1 LTC4268CDKD-1#TR 42681 32-Lead (7mm 4mm) Plastic DFN 0C to 70C
LTC4268IDKD-1 LTC4268IDKD-1#TR 42681 32-Lead (7mm 4mm) Plastic DFN 40C to 85C
Consult LTC Marketing for parts specified with wider operating temperature ranges. *The temperature grade is identified by a label on the shipping container.
For more information on lead free part marking, go to: