LTC4270_12 Datasheet, PDF (1/32 Pages) Linear Technology – 12-Port PoE/PoE+/LTPoE++ PSE Controller

Features
n _{12 Independent PSE Channels}
n _{Compliant with IEEE 802.3at Type 1 and 2}
n _{Chipset Provides Electrical Isolation}
Reduced BOM Cost
Eliminates up to 6 High Speed Opto-Couplers
Eliminates Isolated 3.3V Power Supply
n _{Low Power Dissipation}
0.25Ω Sense Resistance Per Channel
n _{Very High Reliability 4-Point PD Detection}
2-Point Forced Voltage
2-Point Forced Current
n _{VEE and VPORT Monitoring}
n _{1 Second Rolling IPORT Averaging}
n _{Supports 2-Pair and 4-Pair Output Power}
n _{1MHz I}²_{C Compatible Serial Control Interface}
n _{Available In Three Power Grades}
A-Grade – LTPoE++^™ 38.7W to 90W
B-Grade – PoE+ 25.5W
C-Grade – PoE 13W
n _{Available In 52-Lead 7mm × 8mm (LTC4270)}
and 24-Lead 4mm × 4mm (LTC4271) QFN Packages
Applications
n _{PoE PSE Switches/Routers}
n _{PoE PSE Midspans}
LTC4270/LTC4271
12-Port PoE/PoE+/LTPoE++
PSE Controller
Description
The LTC^®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 current
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 I²C
serial interface operable up to 1MHz.
The LTC4270/LTC4271 is available in multiple power
grades allowing delivered PD power up to 90W.
L, LT, LTC, LTM, 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.
Typical Application
3.3V 0.1µF
NO ISOLATION
REQUIRED ON
I²C INTERFACE
GP0
GP1
MID
RESET
MSD
AUTO
INT
V_DD33
SCL ^LTC4271
SDAIN
SDAOUT
CPD
3.3V
CND
DPD
AD0
AD1
AD2
AD3
AD6 _DGND
3.3V
DND
CAP1
1µF
XIO0 XIO1
CPA
100Ω _{• •} 100Ω
–54V
100Ω
100Ω
CNA
DPA
100Ω _{• •} 100Ω
–54V
OUTn
GATEn
SENSEn
LTC4270
OUT1
0.22µF
100V
0.25Ω
0.22µF
100V
100Ω
2nF 2kV
100Ω
DNA
CAP2 VEE
0.1µF
–54V
GATE1
SENSE1
VSSK AGND
0.25Ω
>47µF ⁺
1µF ^SYSTEM
BULK CAP
–54V
S1B
PORTn
S1B
–54V
S1B
PORT1
S1B
–54V
42701 TA01a
LTC4270/LTC4271 FAMILY
MAX
LTC4270
DELIVERED
GRADE ISOLATION LTPoE++ PoE+ PoE POWER
A Transformer l l l 90W
B Transformer
l l 25.5W
C Transformer
l 13W
42701fb
1