troller designed for use in IEEE 802.3 Type 1 and Type 2
(high power) compliant Power over Ethernet systems.
External power MOSFETs enhance system reliability and
minimize channel resistance, cutting power dissipation and
eliminating the need for heatsinks even at Type 2 power
levels. External power components also allow use at very
high power levels while remaining otherwise compatible
with the IEEE standard. 80V-rated port pins provide robust
protection against external faults.
The LTC4274 includes advanced power management
features, including current and voltage readback and pro-
grammable I
CUT
and I
LIM
thresholds. Available C libraries
simplify software development; an optional AUTO pin mode
provides fully IEEE-compliant standalone operation with
no software required. Proprietary 4-point PD detection
circuitry minimizes false PD detection while supporting
legacy phone operation. Midspan operation is supported
with built-in 2-event classification and backoff timing.
Host communication is via a 1MHz I
2
C serial interface.
The LTC4274 is available in a 5mm × 7mm QFN package
that significantly reduces board space compared with
competing solutions.
n
n
n
n
n
n
n
Compliant with IEEE 802.3at Type 1 and 2
0.34Ω Total Channel Resistance
130mW/Port at 600mA
Advanced Power Management
8-Bit Programmable Current Limit (I
LIM
)
7-Bit Programmable Overload Currents (I
CUT
)
Fast Shutdown
14.5-Bit Port Current/Voltage Monitoring
2-Event Classification
Very High Reliability 4-Point PD Detection:
2-Point Forced Voltage
2-Point Forced Current
High Capacitance Legacy Device Detection
LTC4259A-1 and LTC4266 SW Compatible
1MHz I
2
C Compatible Serial Control Interface
Midspan Backoff Timer
Supports Proprietary Power Levels Above 25W
Available in 38-Pin 5mm × 7mm QFN Package
APPLICATIONS
n
n
PSE Switches/Routers
PSE Midspans
L,
LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks and
ThinSOT is a trademark of Linear Technology Corporation. All other trademarks are the property
of their respective owners.
TYPICAL APPLICATION
Complete Ethernet High Power Source
3.3V
0.1μF
INT
SCL
SDAIN
SDAOUT
AD0
AD1
AD2
AD3 DGND AGND
1μF
100V
SHDN
V
DD
AUTO
MSD
RESET
MID
GATE OUT
S1B
0.22μF
100V
PORT
4274 TA01
LTC4274
V
EE
SENSE
SMAJ58A
–54V
S1B
–54V
4274fa
1
LTC4274
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,
ADn,
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
LTC4274C ................................................ 0°C to 70°C
LTC4274I..............................................–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
SHDN
DGND
DGND
DGND
AGND
V
DD
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
LTC4274CUHF#PBF
LTC4274IUHF#PBF
PACKAGE DESCRIPTION
TEMPERATURE RANGE
0°C to 70°C
38-Lead (5mm
×
7mm) Plastic QFN
–40°C to 85°C
38-Lead (5mm
×
7mm) Plastic QFN
Consult LTC Marketing for parts specified with wider operating temperature ranges. *The temperature grade is identified by a label on the shipping container.
Consult LTC Marketing for information on non-standard lead based finish parts.
TAPE AND REEL
LTC4274CUHF#TRPBF
LTC4274IUHF#TRPBF
PART MARKING*
4274
4274
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/
4274fa
2
LTC4274
ELECTRICAL CHARACTERISTICS
SYMBOL
PARAMETER
–48V 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 Complaint Output
For IEEE Type 2 Complaint Output
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
l
l
l
l
l
l
l
l
l
l
l
l
l
MIN
45
51
20
3.0
25
TYP
MAX
57
57
UNITS
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 Lock-out Level
V
DD
V
DD
Supply Voltage
Undervoltage Lock-out
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
2.4
500
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
Min. Valid Signature Resistance
Max. 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
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
0.12
30
14
2.8
700
V
V
kΩ
Output Voltage Sense
V
PG
Power Good Threshold Voltage
OUT Pin Pull-Up Resistance to AGND
4274fa
3
LTC4274
ELECTRICAL CHARACTERISTICS
SYMBOL
V
CUT
PARAMETER
Overcurrent Sense Voltage
Current Sense
V
SENSE
– V
EE
, icut1 = hpen = 00h
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
, dblpwr = hpen = 00h
V
EE
= 55V (Note 12)
V
EE
< V
OUT
< A
GND
– 29V
A
GND
– V
OUT
= 0V
hpen = 01h, lim1 = 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)
(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
180
9
4.5
90
26
49
152
TYP
188
9.38
4.69
94
28
52
159
MAX
196
9.75
4.88
98
30
55
166
UNITS
mV
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
204
40
204
100
20
102
204
2.6
1.3
160
75
212
220
100
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
50-60Hz Noise Rejection
Port Voltage ReadBack
Resolution
LSB Weight
50-60Hz noise rejection
Digital Interface
V
ILD
V
IHD
Digital Input Low Voltage
Digital Input High Voltage
Digital Output Low Voltage
Internal Pull-Up to V
DD
Internal Pull-Down to DGND
0.8
2.2
0.4
0.7
50
50
V
V
V
V
kΩ
kΩ
4274fa
4
LTC4274
ELECTRICAL CHARACTERISTICS
SYMBOL
t
DET
t
DETDLY
t
CLE1
t
ME1
t
CLE2
t
ME2
t
CLE3
t
PON
PARAMETER
Detection Time
Detection Delay
First Class Event Duration
First Mark Event Duration
Second Class Event Duration
Second Mark Event Duration
Third Class 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
ICUT
Timing Characteristics
Beginning to End of Detection (Note 7)
From PD Connected to Port to Detection
Complete (Note 7)
(Note 7)
(Notes 7, 11)
(Note 7)
(Note 7)
C
PORT
= 0.6μF (Note 7)
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)
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
11
6.8
11
19
12
8.6
12
22
0.1
60
15
24
10
1.0
2.3
1.0
52
52
5.8
1.6
320
350
1.1
2.5
1.3
62.5
62.5
6.3
2.7
2.5
66
66
6.7
3.6
380
6.5
6.5
1.5
3
3
4.5
2
3
TYP
290
MAX
310
470
13
10.3
13
UNITS
ms
ms
ms
ms
ms
ms
ms
ms
μs
V/μs
s
s
s
ms
ms
%
ms
ms
μs
μs
s
μs
μs
μs
Maximum Current Limit Duration During Port t
START1
= 0, t
START0
= 0 (Notes 7, 12)
Start-Up
Maximum Current Limit Duration After Port
Start-Up
Maximum Current Limit Duty Cycle
t
ICUT1
= 0, t
ICUT0
= 0 (Notes 7, 12)
(Note 7)
t
MPS
t
DIS
t
MSD
t
SHDN
Maintain Power Signature (MPS) Pulse Width Current Pulse Width to Reset Disconnect
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