LT4276AI/LT4276BI/LT4276CI..............–40°C to 85°C
LT4276AH/LT4276BH/LT4276CH ....... –40°C to 125°C
Storage Temperature Range .................. –65°C to 150°C
28 27 26 25 24 23
GND 1
AUX 2
RCLASS++/NC* 3
RCLASS 4
T2P/NC** 5
V
CC
6
V
CC
7
V
CC
8
UFD PACKAGE
28-LEAD (4mm
×
5mm) PLASTIC QFN
T
JMAX
= 150°C,
θ
JC
= 3.4°C/W
EXPOSED PAD (PIN 29) IS GND, MUST BE SOLDERED TO PCB
*RCLASS++ is not connected in the LT4276B and LT4276C
**T2P is not connected in the LT4276C
orDer inForMaTion
LEAD FREE FINISH
LT4276AIUFD#PBF
LT4276AHUFD#PBF
LT4276BIUFD#PBF
LT4276BHUFD#PBF
LT4276CIUFD#PBF
LT4276CHUFD#PBF
TAPE AND REEL
LT4276AIUFD#TRPBF
LT4276AHUFD#TRPBF
LT4276BIUFD#TRPBF
LT4276BHUFD#TRPBF
LT4276CIUFD#TRPBF
LT4276CHUFD#TRPBF
PART MARKING* MAX PD POWER PACKAGE DESCRIPTION
4276A
4276A
4276B
4276B
4276C
4276C
90W
90W
25.5W
25.5W
13W
13W
28-Lead (4mm
×
5mm) Plastic QFN
28-Lead (4mm
×
5mm) Plastic QFN
28-Lead (4mm
×
5mm) Plastic QFN
28-Lead (4mm
×
5mm) Plastic QFN
28-Lead (4mm
×
5mm) Plastic QFN
28-Lead (4mm
×
5mm) Plastic QFN
TEMPERATURE RANGE
–40°C to 85°C
–40°C to 125°C
–40°C to 85°C
–40°C to 125°C
–40°C to 85°C
–40°C to 125°C
Consult LTC Marketing for parts specified with wider operating temperature ranges. *The temperature grade is identified by a label on the shipping container.
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/.
Some packages are available in 500 unit reels through
designated sales channels with #TRMPBF suffix.
2
4276fa
For more information
www.linear.com/LT4276
LT4276
The
l
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
J
= 25°C. V
VPORT
= V
HSSRC
= V
VIN
= 40V, V
VCC
= VCCREG, ROSC, PG, and SG Open,
R
FFSDLY
= 5.23kΩ to GND. AUX connected to GND unless otherwise specified. (Note 2)
SYMBOL
V
SIG
V
CLASS
V
MARK
PARAMETER
VPORT, HSSRC, V
IN
Operating Voltage
VPORT Signature Range
VPORT Classification Range
VPORT Mark Range
VPORT AUX Range
Signature/Class Hysteresis Window
Reset Threshold
V
HSON
V
HSOFF
Hot Swap Turn-On Voltage
Hot Swap Turn-Off Voltage
Hot Swap On/Off Hysteresis Window
Supply Current
VPORT, HSSRC & V
IN
Supply Current
VPORT Supply Current During Mark Event
Signature and Classification
Signature Resistance
Signature Resistance During Mark Event
RCLASS/RCLASS++ Voltage
Classification Stability Time
Digital Interface
V
AUXT
I
AUXH
AUX Threshold
AUX Pin Current
T2P Output High
T2P Leakage
Hot Swap Control
I
GPU
HSGATE Pull Up Current
HSGATE Voltage
HSGATE Pull Down Current
V
CC
Supply
VCCREG
V
FB
gm
I
SINK
Soft-Start
I
SFST
Charging Current
V
SFST
= 0.5V, 3.0V
l
elecTrical characTerisTics
CONDITIONS
At VPORT Pin
At VPORT Pin
At VPORT Pin
At VPORT Pin, After 1st Classification Event
At VPORT Pin, V
AUX
≥ 6.45V
l
l
l
l
l
l
l
l
l
l
MIN
1.5
12.5
5.6
8
1.0
2.6
TYP
MAX
60
10
21
10
60
5.6
UNITS
V
V
V
V
V
V
V
V
V
V
35
30
3
31
37
V
VPORT
= V
HSSRC
= V
VIN
= 60V
V
VPORT
= V
MARK
after 1st Classification Event
V
SIG
(Note 4)
V
MARK
(Note 4)
–10mA ≥ I
RCLASS
≥ –36mA
V
VPORT
Step to 17.5V, R
CLS
= 35.7Ω
V
PORT
= 17.5V, V
IN
= V
HSSRC
= 18.5V
V
AUX
= 6.05V, V
PORT
= 17.5V, V
IN
= 9V, V
CC
= 0V
V
VCC
- V
T2P
, –1mA Load
V
T2P
= 0V
V
HSGATE
- V
HSSRC
= 5V (Note 5)
–10µA Load, with respect to HSSRC
V
HSGATE
- V
HSSRC
= 5V
l
l
l
2
0.7
0.4
23.6
5.2
1.36
24.4
8.3
1.40
1.0
1.3
2.2
25.5
11.4
1.43
2
6.05
3.3
–1
–27
10
400
7.2
3.11
–52
4.4
–49
7.6
3.17
-0.1
–40
8.0
–42
8.0
3.23
–26
13.4
–36
–22
6.25
5.3
6.45
7.3
0.3
1
–18
14
mA
mA
mA
kΩ
kΩ
V
ms
V
µA
V
µA
µA
V
µA
V
V
µA
µA/V
µA
µA
VPORT Supply Current During Classification V
VPORT
= 17.5V, RCLASS, RCLASS++ Open
l
l
l
l
l
l
l
l
l
l
l
V
CC
Regulation Voltage
FB31 Regulation Voltage
FB31 Pin Bias Current
Feedback Amplifier Average Trans-
Conductance
ITHB Average Sink Current
RLDCMP Open
Time Average, –2µA < I
ITHB
< 2µA
Time Average, V
FB31
= 0V
l
Feedback Amplifier
l
l
l
4276fa
For more information
www.linear.com/LT4276
3
LT4276
The
l
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
J
= 25°C. V
VPORT
= V
HSSRC
= V
VIN
= 40V, V
VCC
= VCCREG, ROSC, PG, and SG Open,
R
FFSDLY
= 5.23kΩ to GND. AUX connected to GND unless otherwise specified. (Note 2)
SYMBOL
PARAMETER
PG, SG Output High Level
PG, SG Output Low Level
PG Rise Time, Fall Time
SG Rise Time, Fall Time
Current Sense/Overcurrent
V
FAULT
ΔV
SENSE
/
ΔV
ITHB
V
ITHB(OS)
Timing
f
OSC
f
T2P
t
MIN
D
MAX
t
PGDELAY
Default Switching Frequency
Switching Frequency
LTPoE++ Signal Frequency
Minimum PG On Time
Maximum PG Duty Cycle
PG Turn-On Delay-Flyback
PG Turn-On Delay-Forward
t
FBDLY
t
FB
t
PGSG
t
START
t
FAULT
I
MPS
Feedback Amp Enable Delay Time
Feedback Amp Sense Interval
PG Falling to SG Rising Delay Time-Flyback
PG Falling to SG Falling Delay Time-
Forward
Start Timer (Note 6)
Fault Timer (Note 6)
MPS Current
Resistor from FFSDLY to GND
10.5kΩ from FFSDLY to V
CC
52.3kΩ from FFSDLY to V
CC
Delay After Power Good
Delay After Overcurrent Fault
l
l
l
elecTrical characTerisTics
Gate Outputs
CONDITIONS
I = –1mA
I = 1mA
PG = 1000pF
SG = 400pF
V
ISEN
+ - V
ISEN
–
l
l
l
l
l
MIN
V
CC
–0.1
TYP
MAX
UNITS
V
1
15
15
125
–130
3.03
200
280
175
63
140
–111
3.17
214
300
f
SW
/256
250
66
45
171
92
391
350
550
20
67
301
80
80
10
86
86
12
93
93
14
155
–98
3.33
223
320
330
70
V
ns
ns
mV
mV/V
V
kHz
kHz
ns
%
ns
ns
ns
ns
ns
ns
ns
ns
ns
ms
ms
mA
Overcurrent Fault Threshold
Current Sense Comparator Threshold with
Respect to V
ITHB
V
ITHB
Offset
ROSC Pin Open
R
OSC
= 45.3kΩ to GND
l
l
l
l
5.23kΩ from FFSDLY to GND
52.3kΩ from FFSDLY to GND
10.5kΩ from FFSDLY to V
CC
52.3kΩ from FFSDLY to V
CC
Note 1:
Stresses beyond those listed under Absolute Maximum Ratings
may cause permanent damage to the device. Exposure to any Absolute
Maximum Rating condition for extended periods may affect device
reliability and lifetime.
Note 2.
All voltages with respect to GND unless otherwise noted. Positive
currents are into pins; negative currents are out of pins unless otherwise
noted.
Note 3.
This IC includes overtemperature protection that is intended
to protect the device during momentary overload conditions. Junction
temperature can exceed 150°C when overtemperature protection is active.
Continuous operation above the specified maximum operating junction
temperature may impair device reliability.
Note 4.
Signature resistance specifications do not include resistance
added by the external diode bridge which can add as much as 1.1kΩ to the
port resistance.
Note 5.
I
GPU
available in PoE powered operation. That is, available after
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