Voltages .......................... –0.3V to 8V (and ≤ VPORT)
AUX Current ........................................................ ±1.4mA
T2P,
PWRGD Voltage ............................... –0.3V to 100V
T2P,
PWRGD Current ...............................................5mA
Operating Junction Temperature Range (Note 4)
LT4294I ................................................–40°C to 85°C
LT4294H ............................................ –40°C to 125°C
Storage Temperature Range .................. –65°C to 150°C
Lead Temperature (Soldering, 10 sec.).................. 300°C
PIN CONFIGURATION
TOP VIEW
GND
AUX
RCLASS
RCLASS++
GND
1
2
3
4
5
11
GND
10 VPORT
9 HSGATE
8 HSSRC
7 PWRGD
6
T2P
TOP VIEW
GND
AUX
RCLASS
RCLASS++
GND
1
2
3
4
5
10
9
8
7
6
VPORT
HSGATE
HSSRC
PWRGD
T2P
DD PACKAGE
10-LEAD (3mm
×
3mm) PLASTIC DFN
T
JMAX
= 150°C,
θ
JC
= 5°C/W
EXPOSED PAD (PIN 11) IS GND, MUST BE SOLDERED TO PCB GND
MS PACKAGE
10-LEAD PLASTIC MSOP
T
JMAX
= 150°C,
θ
JC
= 45°C/W
ORDER INFORMATION
LEAD FREE FINISH
LT4294IDD#PBF
LT4294HDD#PBF
LT4294IMS#PBF
LT4294HMS#PBF
TAPE AND REEL
LT4294IDD#TRPBF
LT4294HDD#TRPBF
LT4294IMS#TRPBF
LT4294HMS#TRPBF
PART MARKING*
LHBX
LHBX
LTHBW
LTHBW
PACKAGE DESCRIPTION
10-Lead (3mm
×
3mm) Plastic DFN
10-Lead (3mm
×
3mm) Plastic DFN
10-Lead Plastic MSOP
10-Lead Plastic MSOP
TEMPERATURE RANGE
–40°C to 85°C
–40°C to 125°C
–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.
The
l
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. (Note 3)
SYMBOL PARAMETER
VPORT Operating Input Voltage
V
SIG
V
CLASS
V
MARK
VPORT Signature Range
VPORT Classification Range
VPORT Mark Range
CONDITIONS
At VPORT Pin
At VPORT Pin
At VPORT Pin
At VPORT Pin, Preceded by V
CLASS
l
l
l
l
ELECTRICAL CHARACTERISTICS
MIN
1.5
12.5
5.6
TYP
MAX
60
10
21
10
UNITS
V
V
V
V
Rev. A
2
For more information
www.analog.com
LT4294
ELECTRICAL CHARACTERISTICS
SYMBOL PARAMETER
VPORT Aux Mode Range
Signature/Class Hysteresis Window
V
RESET
V
HSON
V
HSOFF
Reset Threshold
Hot Swap Turn-On Voltage
Hot Swap Turn-Off Voltage
Hot Swap On/Off Hysteresis Window
Supply Current
Supply Current
Supply Current During Classification
Supply Current During Mark Event
Detection and Classification Signature
Detection Signature Resistance
Resistance During Mark Event
RCLASS/RCLASS++ Operating Voltage
Classification Signature Stability Time
Analog/Digital Interface
V
AUXT
I
AUXH
AUX Threshold
AUX Pin Hysteresis Current
T2P
Output Low
PWRGD Output Low
PWRGD Leakage Current
T2P
Leakage Current
Hot Swap Control
I
GPU
V
GOC
Timing
f
T2P
T2P
Frequency
After PWRGD Valid, if IEEE802.3bt PSE Is Mutually Identified
l
l
The
l
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. (Note 3)
CONDITIONS
At VPORT Pin, AUX > V
AUXT
At VPORT Pin, Preceded by V
CLASS
l
l
l
l
l
l
MIN
8
1.0
2.6
TYP
MAX
60
5.6
UNITS
V
V
V
V
V
V
35
30
3
31
37
V
VPORT
= V
HSSRC
= 57V
V
VPORT
= 17.5V, RCLASS and RCLASS++ Open
V
VPORT
= V
MARK
After 1st Classification Event
V
SIG
(Note 2)
V
MARK
(Note 2)
–10mA ≥ I
RCLASS
≥ –36mA, V
CLASS
V
VPORT
Step to 17.5V,
34.8Ω from RCLASS or RCLASS++ to GND
l
l
l
2
0.4
0.5
23.7
5.8
1.32
24.4
8.3
1.40
0.7
0.9
2.2
25.2
11
1.43
2
mA
mA
mA
kΩ
kΩ
V
ms
l
l
l
l
6.1
3.2
6.3
5
6.5
7
0.8
0.8
5
5
V
µA
V
V
µA
µA
µA
V
µA
V
AUX
= 6.1V
1mA Load
1mA Load
V
PWRGD
= 60V
T2P
= 60V
V
HSGATE
– V
HSSRC
= 5V (Note 6)
–10µA Load, with Respect to HSSRC
V
HSGATE
– V
HSSRC
= 5V
l
l
l
l
l
HSGATE Pull-Up Current
HSGATE Open Circuit Voltage
HSGATE Pull-Down Current
l
l
l
–27
10
200
690
–22
–18
18
840
50
25
25
990
Hz
%
%
%
T2P
Duty Cycle in PoE Operation (Note 5) After 4-Event Classification
After 5-Event Classification
(RCLASS++ Has Resistor to GND)
T2P
Duty Cycle in Auxiliary
V
AUX
> V
AUXT
, and RCLASS++ Has Resistor to GND
Supply Operation (Note 5)
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:
Signature resistance specifications do not include resistance
added by the external diode bridge which can add as much as 1.1k to the
port resistance.
Note 3:
All voltages with respect to GND unless otherwise noted. Positive
currents are into pins; negative currents are out of pins unless otherwise
noted.
Note 4:
This IC includes overtemperature protection that is intended
to protect the device during momentary overload conditions. Junction
temperature will exceed 150°C when overtemperature protection is active.
Continuous operation above the specified maximum operating junction
temperature may impair device reliability.
Note 5:
Specified as the percentage of the period which
T2P
is low
impedance with respect to GND.
Note 6:
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.
For more information
www.analog.com
3
Rev. A
LT4294
TYPICAL PERFORMANCE CHARACTERISTICS
Input Current vs Input Voltage 25k
Detection Signature Range
0.5
T = –40°C
T = 25°C
T = 75°C
T = 125°C
VPORT VOLTAGE (V)
37
36
35
34
33
32
31
0
0
2
4
6
VPORT VOLTAGE (V)
8
10
4294 G01
VPORT Hot Swap Thresholds
2.0
Hot Swap ON
SUPPLY CURRENT (mA)
1.5
Supply Current During Power-On
T = –40°C
T = 25°C
T = 75°C
T = 125°C
0.4
VPORT CURRENT (mA)
0.3
1.0
0.2
0.1
0.5
Hot Swap OFF
0
30
–50
–25
0
25
50
75
TEMPERATURE (°C)
100
125
35
40
45
50
VPORT VOLTAGE (V)
55
60
4294 G03
4294 G02
Detection Signature Resistance
vs Input Voltage
26.25
T = –40°C
T = 25°C
T = 75°C
T = 125°C
VPORT VOLTAGE (V)
1
3
5
7
VPORT VOLTAGE (V)
9
4294 G04
Reset Threshold
5.6
5.1
4.6
4.1
3.6
3.1
2.6
–50
SIGNATURE RESISTANCE (k )
25.75
25.25
24.75
24.25
23.75
–25
0
25
50
75
TEMPERATURE (°C)
100
125
4294 G05
PWRGD,
T2P
Output Low
Voltage vs Current
4
T = –40°C
T = 25°C
T = 75°C
T = 125°C
VPORT VOLTAGE (V)
12.5
VPORT Classification Thresholds
DETECT OR MARK TO CLASS
CLASS TO MARK
T2P
FREQUENCY (Hz)
990
940
890
840
790
740
T2P
Frequency
3
VOLTAGE (V)
12.0
11.5
2
11.0
1
10.5
0
0
1
2
3
CURRENT (mA)
4
5
4294 G06
10.0
–50
–25
0
25
50
75
TEMPERATURE (°C)
100
125
690
–50
–25
0
25
50
75
TEMPERATURE (°C)
100
125
4294 G07
4294 G08
4
Rev. A
For more information
www.analog.com
LT4294
PIN FUNCTIONS
GND (Pins 1, 5, DFN Exposed Pad Pin 11):
Device Ground.
Exposed Pad must be electrically and thermally connected
to pin 5 and PCB GND.
AUX (Pin 2):
Auxiliary Sense. A resistive divider from the
auxiliary power input to AUX sets the voltage at which the
auxiliary supply takes over. In auxiliary power operation,
HSGATE pulls down, the signature resistor disconnects,
classification is disabled, the PWRGD pin is high imped-
ance and
T2P
indicates max available power. The AUX pin
sinks I
AUXH
when below its threshold voltage of V
AUXT
to
provide hysteresis. Connect to GND when not used.
RCLASS (Pin 3):
Configurable PoE Classification Resistor.
See Table 2.
RCLASS++ (Pin 4):
Configurable PoE Classification Resis-
tor. See Table 2.
T2P
(Pin 6):
PSE Type Indicator, Open-Drain Output. See
the Applications Information section for pin behavior.
