LT4295I ................................................–40°C to 85°C
LT4295H ............................................ –40°C to 125°C
Storage Temperature Range .................. –65°C to 150°C
28 27 26 25 24 23
GND 1
AUX 2
RCLASS++ 3
RCLASS 4
T2P 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
ORDER INFORMATION
LEAD FREE FINISH
LT4295IUFD#PBF
LT4295HUFD#PBF
TAPE AND REEL
LT4295IUFD#TRPBF
LT4295HUFD#TRPBF
PART MARKING*
4295
4295
PACKAGE DESCRIPTION
28-Lead (4mm
×
5mm) Plastic QFN
28-Lead (4mm
×
5mm) Plastic QFN
TEMPERATURE RANGE
–40°C to 85°C
–40°C to 125°C
Contact the factory for parts specified with wider operating temperature ranges. *The temperature grade is identified by a label on the shipping container.
Tape and reel specifications.
Some packages are available in 500 unit reels through designated sales channels with #TRMPBF suffix.
NC
2
Rev. A
For more information
www.analog.com
LT4295
ELECTRICAL CHARACTERISTICS
SYMBOL
V
SIG
V
CLASS
V
MARK
PARAMETER
VPORT, HSSRC, V
IN
Operating Voltage
VPORT Detection Signature Range
VPORT Classification Signature Range
VPORT Mark Event Range
VPORT AUX Range
Detect/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 and V
IN
Supply Current
VPORT Supply Current During Mark Event
Detection and Classification Signature
Detection Signature Resistance
Resistance During Mark Event
RCLASS/RCLASS++ Voltage
Classification Signature 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
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)
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
CLASS
V
VPORT
Step GND to 17.5V,
35.7Ω from RCLASS to GND
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
mA
mA
mA
kΩ
kΩ
V
ms
VPORT Supply Current During Classification V
VPORT
= 17.5V, RCLASS, RCLASS++ Open
l
l
l
l
l
l
l
l
6.05
3.3
–1
–27
10
400
7.2
3.11
–52
4.4
–49
6.25
5.3
6.45
7.3
0.3
1
V
µA
V
µA
µA
V
µA
l
l
l
–22
–18
14
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
7.6
3.17
-0.1
–40
8.0
–42
8.0
3.23
–26
13.4
–36
V
V
µA
µA/V
µA
µA
Feedback Amplifier
l
l
l
For more information
www.analog.com
3
Rev. A
LT4295
ELECTRICAL CHARACTERISTICS
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
Default Switching Frequency
Switching Frequency
T2P Signal Frequency
T2P Duty Cycle in PoE Operation (Note 7)
After 4-Event Classification
After 5-Event Classification
(R
CLASS++
Has Resistor to GND)
V
(AUX)
> V
AUXT
, and R
CLASS++
Has Resistor to
GND
l
l
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)
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
Gate Outputs
1
15
15
125
–130
3.03
200
280
140
–111
3.17
214
300
f
SW
/256
50
25
25
175
63
250
66
45
171
92
391
350
550
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
V
ns
ns
Overcurrent Fault Threshold
Current Sense Comparator Threshold with
Respect to V
ITHB
V
ITHB
Offset
155
–92
3.33
223
320
mV
mV/V
V
kHz
kHz
%
%
%
ROSC Pin Open
45.3kΩ from ROSC to GND
l
l
T2P Duty Cycle in Auxiliary Supply
Operation (Note 7)
t
MIN
D
MAX
t
PGDELAY
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
330
70
ns
%
ns
ns
ns
ns
ns
ns
ns
ns
ns
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
20
67
301
80
80
10
86
86
12
93
93
14
ms
ms
mA
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.
Detection 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
V
(VPORT)
> V
HSON
and V
(AUX)
< V
AUXT
, over the range where V
(VPORT)
is
between V
HSOFF
and 60V.
Note 6.
Guaranteed by design, not subject to test.
Note 7.
Specified as the percentage of the period which T2P is low
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