LTC4270/LTC4271
12-Port PoE/PoE+/LTPoE++
PSE Controller
FEATURES
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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 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.
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.
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12 Independent PSE Channels
Compliant with IEEE 802.3at Type 1 and 2
Chipset Provides Electrical Isolation
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Reduced BOM Cost
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Eliminates up to 6 High Speed Opto-Couplers
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Eliminates Isolated 3.3V Power Supply
Low Power Dissipation
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0.25Ω Sense Resistance Per Channel
Very High Reliability 4-Point PD Detection
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2-Point Forced Voltage
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2-Point Forced Current
V
EE
and V
PORT
Monitoring
1 Second Rolling I
PORT
Averaging
Supports 2-Pair and 4-Pair Output Power
1MHz I
2
C Compatible Serial Control Interface
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
Available In 52-Lead 7mm
×
8mm (LTC4270) and
24-Lead 4mm
×
4mm (LTC4271) QFN Packages
PoE PSE Switches/Routers
PoE PSE Midspans
APPLICATIONS
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TYPICAL APPLICATION
3.3V
0.1µF
GP0
GP1
MID
RESET
MSD
AUTO
INT
SCL
SDAIN
SDAOUT
LTC4271
V
DD33
CPD
100
3.3V
100
CND
DPD
100
3.3V
100
DND
CAP1
1µF
2nF 2kV
1µF
–54V
10
CPA
XIO0
XIO1
OUTn
GATEn
SENSEn
LTC4270
0.25
0.22µF
100V
S1B
PORTn
S1B
–54V
LTC4270/LTC4271 FAMILY
MAX
LTC4270
DELIVERED
++ PoE+ PoE POWER
GRADE ISOLATION LTPoE
A
B
C
Transformer
Transformer
Transformer
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NO ISOLATION
REQUIRED ON
I
2
C INTERFACE
•
•
100
–54V
100
CNA
DPA
90W
25.5W
13W
•
•
100
–54V
100
DNA
0.22µF
100V
OUT1
GATE1
S1B
PORT1
S1B
–54V
AD0
AD1
AD2
AD3
AD6 DGND
SENSE1
AGND CAP2 V
EE
VSSK
0.1µF
0.25
>47µF
SYSTEM
BULK CAP
+
–54V
42701 TA01a
42701fd
For more information
www.linear.com/LTC4270
1
LTC4270/LTC4271
ABSOLUTE MAXIMUM RATINGS LTC4270
(Note 1, Note 4)
Supply Voltages
AGND – V
EE
........................................... –0.3V to 80V
VSSK (Note 7) ..................... V
EE
– 0.3V to V
EE
+ 0.3V
Digital Pins
XIOn ................................. V
EE
– 0.3V to CAP2 + 0.3V
Analog Pins
SENSEn, GATEn, OUTn ........ V
EE
– 0.3V to V
EE
+ 80V
CAP2 (Note 13) ....................... V
EE
–0.3V to V
EE
+ 5V
CPA, CNA, DPA, DNA ..............V
EE
– 0.3V to V
EE
+ 0.3
Operating Ambient Temperature Range
LTC4270I .............................................–40°C to 85°C
Junction Temperature (Note 2) ............................ 125°C
Storage Temperature Range ......................–65 to 150°C
ABSOLUTE MAXIMUM RATINGS LTC4271
(Note 1)
Supply Voltages
V
DD
– DGND ......................................... –0.3V to 3.6V
Digital Pins
SCL, SDAIN, SDAOUT,
INT, RESET, MSD,
ADn, AUTO,
MID, GPn ........................DGND – 0.3V to V
DD
+ 0.3V
Operating Ambient Temperature Range
LTC4271I..............................................–40°C to 85°C
Analog Pins
CAP1 (Note 13) ...........................–0.3V to DGND + 2V
CPD, CND, DPD, DND .......... DGND – 0.3 to V
DD
+ 0.3
Junction Temperature (Note 2) ............................ 125°C
Storage Temperature Range ......................–65 to 150°C
2
42701fd
For more information
www.linear.com/LTC4270
LTC4270/LTC4271
PIN CONFIGURATION
LTC4270
TOP VIEW
DNA
CNA
DPA
CPA
LTC4271
V
EE
V
EE
V
EE
NC
NC
NC
NC
52 51 50 49 48 47 46 45 44 43 42 41
SENSE1 1
GATE1 2
OUT1 3
SENSE2 4
GATE2 5
OUT2 6
CAP2 7
SENSE3 8
GATE3 9
OUT3 10
SENSE4 11
GATE4 12
OUT4 13
XIO0 14
15 16 17 18 19 20 21 22 23 24 25 26
SENSE5
GATE5
OUT5
SENSE6
GATE6
OUT6
SENSE7
GATE7
OUT7
SENSE8
GATE8
OUT8
53
VSSK
40 SENSE12
MSD
39 GATE12
38 OUT12
37 SENSE11
36 GATE11
35 OUT11
34 AGND
33 SENSE10
32 GATE10
31 OUT10
30 SENSE9
29 GATE9
28 OUT9
27 XIO1
AD0 1
AD1 2
AD2 3
AD3 4
AD6 5
MID 6
7
NC
8
NC
TOP VIEW
V
DD33
DND
AUTO
CAP1
18 SCL
17 SDAIN
25
DGND
16 SDAOUT
15
INT
14
RESET
13 DNC
9 10 11 12
V
DD33
CND
DPD
GP0
CPD
GP1
24 23 22 21 20 19
UF PACKAGE
24-LEAD (4mm
×
4mm) PLASTIC QFN
T
JMAX
= 125°C,
θ
JA
= 37°C/W
EXPOSED PAD (PIN 25) IS DGND, MUST BE SOLDERED TO PCB
UKG PACKAGE
52-LEAD (7mm
×
8mm) PLASTIC QFN
T
JMAX
= 125°C,
θ
JA
= 40°C/W
EXPOSED PAD (PIN 53) IS VSSK, MUST BE SOLDERED TO PCB
ORDER INFORMATION
LEAD FREE FINISH
LTC4271IUF#PBF
LTC4270AIUKG#PBF
LTC4270BIUKG#PBF
LTC4270CIUKG#PBF
TAPE AND REEL
LTC4271IUF#TRPBF
LTC4270AIUKG#TRPBF
LTC4270BIUKG#TRPBF
LTC4270CIUKG#TRPBF
PART MARKING
4271
LTC4270AUKG
LTC4270BUKG
LTC4270CUKG
PACKAGE DESCRIPTION
24-Lead (4mm
×
4mm) Plastic QFN
52-Lead (7mm
×
8mm) Plastic QFN
52-Lead (7mm
×
8mm) Plastic QFN
52-Lead (7mm
×
8mm) Plastic QFN
90W
25.5W
13W
MAX PWR TEMPERATURE RANGE
–40°C to 85°C
–40°C to 85°C
–40°C to 85°C
–40°C to 85°C
Consult LTC Marketing for parts specified with wider operating temperature ranges.
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/
42701fd
For more information
www.linear.com/LTC4270
3
LTC4270/LTC4271
The
l
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. AGND – V
EE
= 54V and V
DD
– DGND = 3.3V unless otherwise noted.
(Notes 3 & 4)
SYMBOL PARAMETER
V
EE
Main PoE Supply Voltage
CONDITIONS
AGND – V
EE
For IEEE Type 1 Compliant Output
For IEEE Type 2 Compliant Output
For LTPoE++ Compliant Output
AGND – V
EE
V
DD
– DGND
V
DD
– DGND
V
CAP1
– DGND
V
CAP2
– V
EE
(AGND – V
EE
) = 55V
V
EE
< 15V
(V
DD
– DGND) = 3.3V
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ELECTRICAL CHARACTERISTICS
MIN
45
51
54.75
20
3.0
TYP
MAX
57
57
57
UNITS
V
V
V
V
V
V
V
V
Undervoltage Lock-Out
V
DD
V
CAP1
V
CAP2
I
EE
R
EE
I
DD
Detection
V
DD
Supply Voltage
Undervoltage Lock-Out
Internal Regulator Supply Voltage
Internal Regulator Supply Voltage
V
EE
Supply Current
V
EE
Supply Resistance
V
DD
Supply Current
25
3.3
2.7
1.84
4.3
9
10
30
3.6
15
12
15
260
180
9
5
0.9
12
0.01
18.5
32
20.5
mA
kΩ
mA
µA
µA
V
V
mA
V
V/µs
kΩ
kΩ
V
mA
mA
mA
mA
mA
mA
V
mA
mA
mA
mA
Detection Current – Forced Current First Point, AGND – V
OUTn
= 9V
Second Point, AGND – V
OUTn
= 3.5V
Detection Voltage – Forced Voltage AGND – V
OUTn
, 5µA ≤ I
OUTn
≤ 500µA
First Point
Second Point
Detection Current Compliance
V
OC
Detection Voltage Compliance
Detection Voltage Slew Rate
Min. Valid Signature Resistance
Max. Valid Signature Resistance
Classification
V
CLASS
Classification Voltage
Classification Current Compliance
Classification Threshold Current
AGND – V
OUTn
, 0mA ≤ I
OUTn
≤ 50mA
V
OUTn
= AGND
Class 0-1
Class 1-2
Class 2-3
Class 3-4
Class 4-Overcurrent
AGND – V
OUTn
, 0.1mA ≤ I
CLASS
≤ 5mA
V
OUTn
= AGND
Port Off, V
GATEn
= V
EE
+ 5V
Port Off, V
GATEn
= V
EE
+ 1V
V
GATEn
= V
EE
+ 5V
V
GATEn
– V
EE
, I
GATEn
= 1µA
AGND – V
OUTn
= 0V
AGND – V
OUTn
, Open Port
AGND – V
OUTn
, C
PORT
= 0.15µF
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220
143
7
3
240
160
8
4
0.8
10.4
15.5
27.5
16.0
53
5.5
13.5
21.5
31.5
45.2
7.5
53
0.4
0.08
8
17
29.7
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61
6.5
14.5
23
33
48
9
61
67
7.5
15.5
24.5
34.9
50.8
10
67
V
MARK
Classification Mark State Voltage
Mark State Current Compliance
Gate Driver
GATE Pin Pull-Down Current
GATE Pin Fast Pull-Down Current
GATE Pin On Voltage
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0.12
30
12
14
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V
4
42701fd
For more information
www.linear.com/LTC4270
LTC4270/LTC4271
The
l
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. AGND – V
EE
= 54V and V
DD
– DGND = 3.3V unless otherwise noted.
(Notes 3 & 4)
SYMBOL PARAMETER
Output Voltage Sense
V
PG
Power Good Threshold Voltage
OUT Pin Pull-Up Resistance to
AGND
V
CUT
Overcurrent Sense Voltage
V
OUTn
– V
EE
0V ≤ (AGND – V
OUT
) ≤ 5V
V
SENSEn
– V
EE
,
hpen = 0Fh, cutn = D4h
hpen = 0Fh, cutn = E2h (Note 12)
Class 0, Class 3
Class 1
Class 2
Class 4
V
SENSEn
– V
EE
, hpen = 0Fh, limn = 80h, (AGND–V
EE
) = 55V
V
EE
< V
OUT
< AGND – 29V
AGND – V
OUT
= 0V (Note 12)
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ELECTRICAL CHARACTERISTICS
CONDITIONS
MIN
2
300
TYP
2.4
500
MAX
2.8
700
UNITS
V
kΩ
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89
152
89
26
49
152
102
25
204
102
25
102
204
2.6
1.3
125
70
94
159
94
28
52
159
106
99
168
99
30
55
168
112
50
225
115
50
112
225
4.9
2.45
255
125
mV
mV
mV
mV
mV
mV
mV
mV
mV
mV
mV
mV
mV
mV
mV
mV
mV
Bits
µV/LSB
ms/
Convert
Bits
mV/LSB
Overcurrent Sense in AUTO Pin
Mode
V
LIM
Active Current Limit in 802.3af
Compliant Mode
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Active Current Limit in High Power hpen = 0Fh, limn = C0h, AGND–V
EE
= 55V
Mode
V
OUT
– V
EE
= 0 – 10V
V
EE
+ 23V < V
OUT
< AGND – 29V
AGND – V
OUT
= 0V (Note 12)
Active Current Limit in AUTO Pin
Mode
V
MIN
V
SC
DC Disconnect Sense Voltage
Short-Circuit Sense
V
EE
< V
OUT
< AGND – 10V, AGND–V
EE
= 55V
Class 0 to Class 3
Class 4
V
SENSE
– V
EE
, rdis Bit = 0
V
SENSE
– V
EE
, rdis Bit = 1 (Note 12)
V
SENSEn
– V
EE
– V
LIM
(Note 12)
rdis Bit = 0
rdis bit = 1
No Missing Codes, Reported as 14-Bits
V
SENSEn
– V
EE
l
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212
106
l
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l
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106
212
3.8
1.9
200
100
12
30.518
25.1
Port Current Readback
Resolution
LSB Weight
Conversion Period
Port Voltage Readback
Resolution
LSB Weight
Digital Interface
V
ILD
V
IHD
Digital Input Low Voltage
I
2
C Input Low Voltage
Digital Input High Voltage
Digital Output Voltage Low
Internal Pull Up to V
DD
Internal Pull Down To DGND
ADn,
RESET, MSD,
GPn, AUTO, MID (Note 6)
SCL, SDAIN (Note 6)
(Note 6)
I
SDAOUT
= 3mA, I
INT
= 3mA
I
SDAOUT
= 5mA, I
INT
= 5mA
ADn,
RESET, MSD,
GPn
AUTO, MID
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l
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No Missing Codes, Reported as 14-Bits
V
SENSEn
– V
EE
12
5.8350
0.8
1.0
2.2
0.4
0.7
50
50
V
V
V
V
V
kΩ
kΩ
42701fd
For more information
www.linear.com/LTC4270
5
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