LTC4270/LTC4271
1
42701fd
For more information www.linear.com/LTC4270
n
PoE PSE Switches/Routers
n
PoE PSE Midspans
APPLICATIONS
TYPICAL APPLICATION
FEATURES
DESCRIPTION
12-Port PoE/PoE
+
/LTPoE
++
PSE Controller
The LT C
®
4270/LTC4271 chipset is a 12-port power sourc-
ing equipment (PSE) controller designed for use in IEEE
802.3at Type 1 and Type 2 (high power) compliant Power
over Ethernet (PoE) systems. Transformer-isolated com-
munication protocol replaces expensive opto-couplers
and complex isolated 3.3V supply resulting in significant
BOM cost savings. The LTC4270/LTC4271 chipset delivers
lowest-in-industry heat dissipation by utilizing low-R
DS(ON)
external MOSFETs and 0.25Ω sense resistors.
Advanced power management features include per-port
12-bit current monitoring ADCs, DAC-programmable cur-
rent limit, and versatile fast shut-down of preselected ports.
Advanced power management host software is available
under a no-cost license. PD discovery uses a proprietary
dual-mode 4-point detection mechanism ensuring excel-
lent immunity from false PD detection. Midspan PSEs
are supported with 2-event classification and a 2 second
backoff timer. The LTC4270/LTC4271 includes an I
2
C
serial interface operable up to 1MHz.
The LTC4270/LTC4271 is available in multiple power
grades allowing delivered PD power up to 90W.
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12 Independent PSE Channels
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Compliant with IEEE 802.3at Type 1 and 2
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Chipset Provides Electrical Isolation
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Reduced BOM Cost
n
Eliminates up to 6 High Speed Opto-Couplers
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Eliminates Isolated 3.3V Power Supply
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Low Power Dissipation
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0.25Ω Sense Resistance Per Channel
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Very High Reliability 4-Point PD Detection
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2-Point Forced Voltage
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2-Point Forced Current
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V
EE
and V
PORT
Monitoring
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1 Second Rolling I
PORT
Averaging
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Supports 2-Pair and 4-Pair Output Power
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1MHz I
2
C Compatible Serial Control Interface
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Available In Three Power Grades
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A-Grade – LTPoE
++
™
38.7W to 90W
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B-Grade – PoE
+
25.5W
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C-Grade – PoE 13W
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Available In 52-Lead 7mm × 8mm (LTC4270) and
24-Lead 4mm × 4mm (LTC4271) QFN Packages
LTC4270/LTC4271 FAMILY
LTC4270
GRADE ISOLATION LTPoE
++
PoE
+
PoE
MAX
DELIVERED
POWER
A Transformer
l l l
90W
B Transformer
l l
25.5W
C Transformer
l
13W
L, LT , LT C , LT M , Burst Mode, Linear Technology and the Linear logo are registered trademarks
and LTPoE
++
is a trademark of Linear Technology Corporation. All other trademarks are the
property of their respective owners.
••
3.3V
3.3V 0.1µF
–54V
100Ω
100Ω
100Ω
100Ω
••
3.3V
1µF 0.1µF
–54V
100Ω
100Ω
100Ω
100Ω
GP0
GP1
MID
RESET
MSD
INT
AUTO
SCL
AD0
AD1
AD2
AD3
AD6
DGND CAP1
CAP2
DND
DPD
CND
CPD
DNA
SENSE1
GATE1
OUT1
LTC4270
DPA
CNA
CPA
XIO0 XIO1
0.22µF
100V
0.22µF
100V
S1B
S1B
–54V
–54V
42701 TA01a
–54V
S1B
S1B
PORTn
PORT1
SDAIN
SDAOUT
LTC4271
NO ISOLATION
REQUIRED ON
I
2
C INTERFACE
V
DD33
2nF 2kV
V
EE
SENSEn
GATEn
OUTn
AGND
VSSK
0.25Ω
0.25Ω
–54V
>47µF
SYSTEM
BULK CAP
+
1µF
10Ω
