FEATURES
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LTC4274A/LTC4274C
Single PoE/PoE+/LTPoE++
PSE Controller
DESCRIPTION
The LTC
®
4274A is a single Power Sourcing Equipment
(PSE) controller capable of delivering up to 90W of LTPoE++
power to a compatible LTPoE++ Powered Device (PD). A
proprietary detection/classification scheme allows mutual
identification between a LTPoE++ PSE and LTPoE++ PD
while remaining compatible and interoperable with existing
Type 1 (13W) and Type 2 (25.5W) PDs. The LTC4274A
feature set is a superset of the popular LTC4274. These
PSE controllers feature low-R
ON
external MOSFETs and
0.25Ω sense resistors which are especially important at
the LTPoE++ current levels to maintain the lowest possible
heat dissipation.
The LTC4274C targets fully automatic PSE systems power-
ing Type 1 (up to 13W) PDs.
Advanced power management features include: a 14-bit
current monitoring ADC, DAC-programmable current limit,
and versatile quick port shutdown. PD Discovery uses
a proprietary dual-mode 4-point detection mechanism
ensuring excellent immunity from false PD detection.
The LTC4274A/LTC4274C includes an I
2
C serial interface
operable up to 1MHz.
The LTC4274A/LTC4274C is available in multiple power
grades, allowing delivered PD power of 13W, 25.5W, 38.7W,
52.7W, 70W and 90W. These controllers are available in a
38-lead 5mm × 7mm QFN package.
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Compliant with IEEE 802.3at Type 1 and 2
Low Power Dissipation
0.25Ω Sense Resistance Per Channel
Very High Reliability 4-Point PD Detection
2-Point Forced Voltage
2-Point Forced Current
High Capacitance Legacy Device Detection
1MHz I
2
C Compatible Serial Control Interface
Midspan Backoff Timer
Supports 2-Pair and 4-Pair Output Power
Available in Multiple Power Grades
LTC4274A-1: LTPoE++
™
38.7W
LTC4274A-2: LTPoE++ 52.7W
LTC4274A-3: LTPoE++ 70W
LTC4274A-4: LTPoE++ 90W
LTC4274C: PoE 13W
Available in 38-Lead 5mm × 7mm QFN Package
APPLICATIONS
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LTPoE++ PSE Switches/Routers
LTPoE++ PSE Midspans
IEEE 802.3at Type 1 PSE Switches/Routers
IEEE 802.3at Type 1 PSE Midspans
L,
LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks and
LTPoE++ are trademarks of Linear Technology Corporation. All other trademarks are the
property of their respective owners.
TYPICAL APPLICATION
Complete Single-Port Ethernet High Power Source
3.3V
0.1μF
INT
SCL
SDAIN
SDAOUT
AD0
AD1
AD2
AD3
DGND AGND
SHDN
V
DD
AUTO
MSD
RESET
MID
LTC4274A/LTC4274C
V
EE
SENSE
1μF
100V
GATE OUT
S1B
0.22μF
100V
PORT
4274AC TA01
SMAJ58A
–54V
S1B
–54V
4274acfc
1
LTC4274A/LTC4274C
ABSOLUTE MAXIMUM RATINGS
Supply Voltages (Note 1)
AGND – V
EE
........................................... –0.3V to 80V
DGND – V
EE
........................................... –0.3V to 80V
V
DD
– DGND ......................................... –0.3V to 5.5V
Digital Pins
SCL, SDAIN, SDAOUT,
INT, SHDN, MSD,
AD,
RESET,
AUTO, MID........... DGND –0.3V to V
DD
+ 0.3V
Analog Pins
GATE, SENSE, OUT ................ V
EE
–0.3V to V
EE
+ 80V
Operating Temperature Range .................–40°C to 85°C
Junction Temperature (Note 2) ............................. 125°C
Storage Temperature Range .................. –65°C to 150°C
Lead Temperature (Soldering, 10 sec)................... 300°C
PIN CONFIGURATION
TOP VIEW
RESET
AUTO
MSD
OUT
31 GATE
30 SENSE
29 NC
28 NC
27 V
EE
V
EE
39
26 V
EE
25 V
EE
24 NC
23 NC
22 V
EE
21 NC
20 NC
13 14 15 16 17 18 19
V
DD
SHDN
DGND
DGND
DGND
AGND
V
EE
MID
SCL
SDAOUT 1
NC 2
SDAIN 3
AD3 4
AD2 5
AD1 6
AD0 7
DNC 8
NC 9
DGND 10
NC 11
NC 12
INT
38 37 36 35 34 33 32
UHF PACKAGE
38-LEAD (5mm 7mm) PLASTIC QFN
EXPOSED PAD IS V
EE
(PIN 39) MUST BE SOLDERED TO PCB
T
JMAX
= 125°C,
JA
= 34°C/W
ORDER INFORMATION
LEAD FREE FINISH
LTC4274CIUHF#PBF
LTC4274AIUHF-1#PBF
LTC4274AIUHF-2#PBF
LTC4274AIUHF-3#PBF
LTC4274AIUHF-4#PBF
TAPE AND REEL
LTC4274CIUHF#TRPBF
LTC4274AIUHF-1#TRPBF
LTC4274AIUHF-2#TRPBF
LTC4274AIUHF-3#TRPBF
LTC4274AIUHF-4#TRPBF
PART MARKING
4274C
4274A1
4274A2
4274A3
4274A4
PACKAGE DESCRIPTION
38-Lead (5mm × 7mm) Plastic QFN
38-Lead (5mm × 7mm) Plastic QFN
38-Lead (5mm × 7mm) Plastic QFN
38-Lead (5mm × 7mm) Plastic QFN
38-Lead (5mm × 7mm) Plastic QFN
MAX PWR
13W
38.7W
52.7W
70W
90W
TEMPERATURE RANGE
–40°C to 85°C
–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/
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2
LTC4274A/LTC4274C
ELECTRICAL CHARACTERISTICS
SYMBOL
V
EE
PARAMETER
Main PoE Supply Voltage
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, AGND = DGND, and V
DD
– DGND = 3.3V
unless otherwise noted. (Notes 3, 4)
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
DGND – V
EE
(AGND – V
EE
) = 55V
(V
DD
– DGND) = 3.3V
First Point, AGND – V
OUT
= 9V
Second Point, AGND – V
OUT
= 3.5V
AGND – V
OUT
, 5μA ≤ I
OUT
≤ 500μA
First Point
Second Point
AGND – V
OUT
= 0V
AGND – V
OUT
, Open Port
AGND – V
OUT
, C
PORT
= 0.15μF
l
l
l
l
l
l
l
l
l
l
l
l
l
l
l
l
l
l
MIN
45
51
54.75
20
3.0
25
TYP
MAX
57
57
57
UNITS
V
V
V
V
V
V
V
mA
mA
μA
μA
V
V
mA
V
V/μs
kΩ
kΩ
V
mA
mA
mA
mA
mA
mA
V
mA
mA
mA
mA
Undervoltage Lockout
V
DD
V
DD
Supply Voltage
Undervoltage Lockout
Allowable Digital Ground Offset
I
EE
I
DD
Detection
Detection Current – Force Current
Detection Voltage – Force Voltage
V
EE
Supply Current
V
DD
Supply Current
25
3.3
2.2
30
4.3
57
–2.4
1.1
220
140
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
2
300
61
6.5
14.5
23
33
48
9
61
17
29.7
–5
3
260
180
9
5
0.9
12
0.01
18.5
32
20.5
67
7.5
15.5
24.5
34.9
50.8
10
67
Detection Current Compliance
V
OC
Detection Voltage Compliance
Detection Voltage Slew Rate
Minimum Valid Signature Resistance
Maximum Valid Signature Resistance
Classification
V
CLASS
Classification Voltage
Classification Current Compliance
Classification Threshold Current
AGND – V
OUT
, 0mA ≤ I
CLASS
≤ 50mA
V
OUT
= AGND
Class 0 – 1
Class 1 – 2
Class 2 – 3
Class 3 – 4
Class 4 – Overcurrent
AGND – V
OUT
, 0.1mA ≤ I
CLASS
≤ 10mA
V
OUT
= AGND
Port Off, V
GATE
= V
EE
+ 5V
Port Off, V
GATE
= V
EE
+ 1V
V
GATE
= V
EE
+ 5V
V
GATE
– V
EE
, I
GATE
= 1μA
V
OUT
– V
EE
0V ≤ (AGND – V
OUT
) ≤ 5V
l
l
l
l
l
l
l
l
l
V
MARK
Gate Driver
Classification Mark State Voltage
Mark State Current Compliance
GATE Pin Pull-Down Current
GATE Pin Fast Pull-Down Current
GATE Pin On Voltage
l
l
l
0.12
30
12
2.4
500
14
2.8
700
V
V
kΩ
Output Voltage Sense
V
PG
Power Good Threshold Voltage
OUT Pin Pull-Up Resistance to AGND
l
l
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3
LTC4274A/LTC4274C
ELECTRICAL CHARACTERISTICS
SYMBOL
V
CUT
PARAMETER
Overcurrent Sense Voltage
Current Sense
V
SENSE
– V
EE
, hpen = 01h, cut[5:0] ≥ 4 (Note 12)
cutrng = 0
cutrng = 1
Class 0, Class 3
Class 1
Class 2
Class 4
V
SENSE
– V
EE
, hpen = 01h, lim = 80h,
V
EE
= 55V (Note 12)
V
EE
< V
OUT
< AGND – 29V
AGND – V
OUT
= 0V
hpen = 01h, lim = C0h, V
EE
= 55V
V
OUT
– V
EE
= 0V to 10V
V
EE
+ 23V < V
OUT
< AGND – 29V
AGND – V
OUT
= 0V
V
OUT
– V
EE
= 0V to 10V, V
EE
= 55V
Class 0 to Class 3
Class 4
V
SENSE
– V
EE
, rdis = 0
V
SENSE
– V
EE
, rdis = 1
V
SENSE
– V
EE
– V
LIM
, rdis = 0
V
SENSE
– V
EE
– V
LIM
, rdis = 1
No Missing Codes, fast_iv = 0
V
SENSE
– V
EE
(Note 7)
No Missing Codes, fast_iv = 0
AGND – V
OUT
(Note 7)
ADn,
SHDN, RESET, MSD,
AUTO, MID
(Note 6)
SCL, SDAIN (Note 6)
(Note 6)
I
SDAOUT
= 3mA, I
INT
= 3mA
I
SDAOUT
= 5mA, I
INT
= 5mA
ADn,
SHDN, RESET, MSD
AUTO, MID
l
l
l
l
l
l
l
l
l
l
l
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, AGND = DGND, and V
DD
– DGND = 3.3V
unless otherwise noted. (Notes 3, 4)
CONDITIONS
MIN
TYP
MAX
UNITS
9
4.5
90
26
49
152
9.38
4.69
94
28
52
159
9.75
4.88
98
30
55
166
mV/LSB
mV/LSB
mV
mV
mV
mV
Overcurrent Sense in AUTO Pin Mode
V
LIM
Active Current Limit in 802.3af
Compliant Mode
l
l
l
l
l
l
l
l
l
l
l
102
20
204
100
20
102
204
2.6
1.3
160
75
106
110
50
221
113
50
110
221
4.8
2.41
255
135
mV
mV
mV
mV
mV
mV
mV
mV
mV
mV
mV
Bits
μV/LSB
dB
bits
mV/LSB
dB
V
LIM
Active Current Limit in High Power Mode
212
106
V
LIM
Active Current Limit in AUTO Pin Mode
106
212
3.8
1.9
200
100
14
30.5
30
14
5.835
30
V
MIN
V
SC
DC Disconnect Sense Voltage
Short-Circuit Sense
Port Current ReadBack
Resolution
LSB Weight
50Hz to 60Hz Noise Rejection
Port Voltage ReadBack
Resolution
LSB Weight
50Hz to 60Hz Noise Rejection
Digital Interface
V
ILD
Digital Input Low Voltage
I
2
C Input Low Voltage
V
IHD
Digital Input High Voltage
Digital Output Low Voltage
Internal Pull-Up to V
DD
Internal Pull-Down to DGND
0.8
0.8
2.2
0.4
0.7
50
50
V
V
V
V
V
kΩ
kΩ
4274acfc
4
LTC4274A/LTC4274C
ELECTRICAL CHARACTERISTICS
SYMBOL
t
DET
t
DETDLY
t
CLE
t
CLEON
t
ME
t
MEL
t
PON
PARAMETER
Detection Time
Detection Delay
Class Event Duration
Class Event Turn-On Duration
Mark Event Duration
Last Mark Event Duration
Power On Delay in AUTO Pin Mode
Turn On Rise Time
Turn On Ramp Rate
Fault Delay
Midspan Mode Detection Backoff
Power Removal Detection Delay
t
START
t
LIM
t
CUT
Maximum Current Limit Duration During
Port Start-Up
Timing Characteristics
Beginning to End of Detection (Note 7)
From PD Connected to Port to Detection
Complete (Note 7)
(Note 7)
C
PORT
= 0.6μF (Note 7)
(Notes 7, 11)
(Notes 7, 11)
From End of Valid Detect to Application of Power
to Port (Note 7)
(AGND – V
OUT
): 10% to 90% of (AGND – V
EE
),
C
PORT
= 0.15μF (Note 7)
C
PORT
= 0.15μF (Note 7)
From I
CUT
Fault to Next Detect
Rport = 15.5kΩ (Note 7)
From Power Removal After t
DIS
to Next Detect
(Note 7)
(Note 7)
l
l
l
l
l
l
l
l
l
l
l
l
l
l
l
l
l
l
l
l
l
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, AGND = DGND, and V
DD
– DGND = 3.3V
unless otherwise noted. (Notes 3, 4)
CONDITIONS
MIN
270
300
12
0.1
8.6
16
22
60
15
24
10
1.0
2.3
1.0
52
1.1
2.5
1.3
62.5
11.9
52
5.8
1.6
320
350
62.5
6.3
66
6.7
3.6
380
6.5
6.5
1.5
3
3
4.5
2
3
2.7
2.5
66
TYP
290
MAX
310
470
UNITS
ms
ms
ms
ms
ms
ms
ms
μs
V/μs
s
s
s
ms
ms
ms
%
ms
ms
μs
μs
s
μs
μs
μs
Maximum Current Limit Duration After Port t
LIM
Enable = 1 (Notes 7, 12)
Start-Up
Maximum Overcurrent Duration After Port
Start-Up
Maximum Overcurrent Duty Cycle
Maintain Power Signature (MPS) Pulse
Width Sensitivity
Maintain Power Signature (MPS) Dropout
Time
Masked Shut Down Delay
Port Shut Down Delay
I
2
C Watchdog Timer Duration
Minimum Pulse Width for Masked Shut
Down
Minimum Pulse Width for
SHDN
Minimum Pulse Width for
RESET
(Note 7)
(Note 7)
(Note 7)
(Note 7)
(Note 7)
Current Pulse Width to Reset Disconnect Timer
(Notes 7, 8)
(Notes 5, 7)
(Note 7)
(Note 7)
t
MPS
t
DIS
t
MSD
t
SHDN
l
l
l
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