FEATURES
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LTC4267-1
Power over Ethernet
IEEE 802.3af PD Interface with
Integrated Switching Regulator
DESCRIPTIO
The LTC
®
4267-1 combines an IEEE 802.3af compliant
Powered Device (PD) interface with a current mode switch-
ing regulator, providing a complete power solution for PD
applications. The LTC4267-1 integrates the 25k signature
resistor, classification current source, thermal overload
protection, signature disable and power good signal along
with an undervoltage lockout optimized for use with the
IEEE-required diode bridge. The LTC4267-1 provides an
increased operational current limit, maximizing power
available for class 3 applications.
The current mode switching regulator is designed for
driving a 6V rated N-channel MOSFET and features pro-
grammable slope compensation, soft-start, and constant
frequency operation, minimizing noise even with light
loads. The LTC4267-1 includes an onboard error amplifier
and voltage reference allowing use in both isolated and
nonisolated configurations.
The LTC4267-1 is available in a space saving, low profile
16-pin SSOP package.
Complete Power Interface Port for IEEE 802
®
.3af
Powered Device (PD)
Onboard 100V, UVLO Switch
Precision Dual Level Inrush Current Limit
Integrated Current Mode Switching Regulator
Onboard 25k Signature Resistor with Disable
Programmable Classification Current (Class 0-4)
Thermal Overload Protection
Power Good Signal
Integrated Error Amplifier and Voltage Reference
Low Profile 16-Pin SSOP Package
APPLICATIO S
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IP Phone Power Management
Wireless Access Points
Security Cameras
Power over Ethernet
, LT, LTC and LTM are registered trademarks of Linear Technology Corporation.
All other trademarks are the property of their respective owners.
TYPICAL APPLICATIO
Class 2 PD with 3.3V Isolated Power Supply
+
+
U
U
U
•
•
42671f
1
LTC4267-1
ABSOLUTE
(Note 1)
AXI U RATI GS
V
PORTN
with Respect to V
PORTP
Voltage ... 0.3V to –100V
P
OUT
, SIGDISA,
⎯
P
⎯
W
⎯
R
⎯
G
⎯
D
Voltage..................... V
PORTN
+ 100V to V
PORTN
–0.3V
P
VCC
to PGND Voltage (Note 2)
Low Impedance Source ........................... –0.3V to 8V
Current Fed .......................................... 5mA into P
VCC
R
CLASS
Voltage .................V
PORTN
+ 7V to V
PORTN
– 0.3V
⎯
P
⎯
W
⎯
R
⎯
G
⎯
D Current .....................................................10mA
R
CLASS
Current.....................................................100mA
NGATE to PGND Voltage ...........................–0.3V to P
VCC
V
FB
, I
TH
/RUN to PGND Voltages ................ –0.3V to 3.5V
SENSE to PGND Voltage .............................. –0.3V to 1V
NGATE Peak Output Current (<10μs) ..........................1A
Operating Ambient Temperature Range
LTC4267C-1 ............................................. 0°C to 70°C
LTC4267I-1 ..........................................–40°C to 85°C
Junction Temperature ........................................... 150°C
Storage Temperature Range...................–65°C to 150°C
Lead Temperature (Soldering, 10 sec) .................. 300°C
ORDER INFORMATION
LEAD FREE FINISH
LTC4267CGN-1#PBF
LTC4267IGN-1#PBF
LEAD BASED FINISH
LTC4267CGN-1
LTC4267IGN-1
TAPE AND REEL
LTC4267CGN-1#TRPBF
LTC4267IGN-1#TRPBF
TAPE AND REEL
LTC4267CGN-1#TR
LTC4267IGN-1#TR
PART MARKING*
4267-1
4267I-1
PART MARKING
4267-1
4267I-1
PACKAGE DESCRIPTION
16-Lead Narrow Plastic SSOP
16-Lead Narrow Plastic SSOP
PACKAGE DESCRIPTION
16-Lead Narrow Plastic SSOP
16-Lead Narrow Plastic SSOP
TEMPERATURE RANGE
0°C to 70°C
–40°C to 85°C
TEMPERATURE RANGE
0°C to 70°C
–40°C to 85°C
Consult LTC Marketing for parts specified with wider operating temperature ranges.
*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/
The
●
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. (Note 3)
SYMBOL
V
PORTN
PARAMETER
Supply Voltage
Maximum Operating Voltage
Signature Range
Classification Range
UVLO Turn-On Voltage
UVLO Turn-Off Voltage
P
VCC
Turn-On Voltage
P
VCC
Turn-Off Voltage
P
VCC
Hysteresis
CONDITIONS
Voltage with Respect to V
PORTP
Pin
(Notes 4, 5, 6)
●
●
●
●
●
●
●
●
ELECTRICAL CHARACTERISTICS
V
TURNON
V
TURNOFF
V
HYST
2
U
W W
W
PIN CONFIGURATION
T
JMAX
= 150°C,
θ
JA
= 90°C/W
MIN
TYP
MAX
–57
–9.5
–21
–37.2
–31.5
9.2
6.8
UNITS
V
V
V
V
V
V
V
V
42671f
–1.5
–12.5
–34.8
–29.3
7.8
4.6
1.5
–36.0
–30.5
8.7
5.7
3.0
Voltage with Respect to PGND
Voltage with Respect to PGND
V
TURNON
– V
TURNOFF
LTC4267-1
The
●
denotes
ELECTRICAL CHARACTERISTICS
25°C. (Note 3) the specifications which apply over the full operating
temperature range, otherwise specifications are at T =
A
SYMBOL
V
CLAMP1mA
V
MARGIN
I
VPORTN_ON
I
PVCC_ON
PARAMETER
P
VCC
Shunt Regulator Voltage
V
CLAMP1mA
– V
TURNON
Margin
V
PORTN
Supply Current when ON
P
VCC
Supply Current
Normal Operation
Start-Up
CONDITIONS
I
PVCC
= 1mA, V
ITH
/RUN = 0V, Voltage
with Respect to PGND
V
PORTN
= –48V, P
OUT
,
⎯
P
⎯
W
⎯
R
⎯
G
⎯
D, SIGDISA Floating
(Note 7)
V
ITH
/RUN – PGND = 1.3V
P
VCC
– PGND = V
TURNON
– 100mV
V
PORTN
= –17.5V, P
OUT
Tied to V
PORTP
, R
CLASS
,
SIGDISA Floating (Note 8)
10mA < I
CLASS
< 40mA, –12.5V ≤ V
PORTN
≤ –21V
(Note 9)
–1.5V ≤ V
PORTN
≤ – 9.5V, P
OUT
Tied to V
PORTP
,
IEEE 802.3af 2-Point Measurement (Notes 4, 5)
–1.5V ≤ V
PORTN
≤ – 9.5V, SIGDISA and P
OUT
Tied to
V
PORTP
, IEEE 802.3af 2-Point Measurement
(Notes 4, 5)
With Respect to V
PORTN
High Level Invalidates Signature (Note 10)
With Respect to V
PORTN
Low Level Enables Signature
With Respect to V
PORTN
I = 1mA V
PORTN
= –48V,
⎯
P
⎯
W
⎯
R
⎯
G
⎯
D Referenced to V
PORTN
V
PORTN
= –48V, Voltage between V
PORTN
and P
OUT
P
OUT
Falling
P
OUT
Rising
V
PORTN
= 0V,
⎯
P
⎯
W
⎯
R
⎯
G
⎯
D FET Off, V
⎯
P
⎯
W
⎯
R
⎯
G
⎯
D
= 57V
I = 300mA, V
PORTN
= –48V, Measured from
V
PORTN
to P
OUT
P
VCC
– PGND = V
TURNON
+ 100mV
V
ITH
/RUN – PGND = 0V, P
VCC
– P
GND
= 8V
Referenced to PGND, P
VCC
– P
GND
= 8V (Note 11)
P
VCC
– P
GND
= 8V (Note 11)
I
TH
/RUN Pin Load = ±5μA (Note 11)
V
TURNOFF
< P
VCC
< V
CLAMP
(Note 11)
I
TH
/RUN Sinking 5μA, P
VCC
– P
GND
= 8V (Note 11)
I
TH
/RUN Sourcing 5μA, P
VCC
– P
GND
= 8V (Note 11)
V
PORTN
= 0V, Power MOSFET Off,
P
OUT
= 57V (Note 12)
V
PORTN
= –48V, P
OUT
= –43V (Note 13, 14)
V
PORTN
= –48V, P
OUT
= –43V (Note 13, 14)
V
ITH
/RUN – PGND = 1.3V, P
VCC
– P
GND
= 8V
V
ITH
/RUN – PGND = 1.3V, V
FB
– PGND = 0.8V,
P
VCC
– P
GND
= 8V
V
ITH
/RUN – PGND = 1.3V, V
FB
– PGND = 0.8V,
P
VCC
– P
GND
= 8V
●
●
●
●
●
●
●
●
●
MIN
8.3
0.05
TYP
9.4
0.6
MAX
10.3
UNITS
V
V
mA
μA
μA
mA
%
kΩ
kΩ
3
240
40
0.5
350
90
0.65
±3.5
23.25
9
26.00
11.8
I
VPORTN_CLASS
V
PORTN
Supply Current
During Classification
ΔI
CLASS
Current Accuracy
During Classification
R
SIGNATURE
Signature Resistance
R
INVALID
Invalid Signature Resistance
0.35
V
IH
V
IL
R
INPUT
V
PG_OUT
Signature Disable
High Level Input Voltage
Signature Disable
Low Level Input Voltage
Signature Disable, Input Resistance
Power Good Output Low Voltage
Power Good Trip Point
●
●
●
●
3
57
0.45
V
V
kΩ
V
100
0.5
V
PG _FALL
V
PG_RISE
I
PG_LEAK
R
ON
V
ITHSHDN
I
THSTART
V
FB
I
FB
g
m
ΔV
O(LINE)
ΔV
O(LOAD)
I
POUT_LEAK
I
LIM_HI
I
LIM_LO
f
OSC
DC
ON(MIN)
DC
ON(MAX)
Power Good Leakage Current
On-Resistance
Shutdown Threshold (at I
TH
/RUN)
Start-Up Current Source at I
TH
/RUN
Regulated Feedback Voltage
V
FB
Input Current
Error Amplifier Transconductance
Output Voltage Line Regulation
Output Voltage Load Regulation
P
OUT
Leakage
Input Current Limit, High Level
Input Current Limit, Low Level
Oscillator Frequency
Minimum Switch On Duty Cycle
Maximum Switch On Duty Cycle
●
●
●
1.3
2.7
1.5
3.0
1.0
●
●
●
0.15
0.2
0.780
200
0.28
0.3
0.800
10
333
0.05
3
3
1.7
3.3
1
1.6
2
0.45
0.4
0.812
50
500
●
●
●
150
350
90
180
450
205
240
8
90
V
V
μA
Ω
Ω
V
μA
V
nA
μA/V
mV/V
mV/μA
mV/μA
μA
mA
mA
kHz
%
%
200
6
80
70
42671f
3
LTC4267-1
ELECTRICAL CHARACTERISTICS
SYMBOL
t
RISE
t
FALL
V
IMAX
I
SLMAX
t
SFST
T
SHUTDOWN
PARAMETER
NGATE Drive Rise Time
NGATE Drive Fall Time
Peak Current Sense Voltage
Peak Slope Compensation Output Current
Soft-Start Time
Thermal Shutdown Trip Temperature
The
●
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. (Note 3)
CONDITIONS
C
LOAD
= 3000pF, P
VCC
– P
GND
= 8V
C
LOAD
= 3000pF, P
VCC
– P
GND
= 8V
R
SL
= 0, P
VCC
– P
GND
= 8V (Note 15)
P
VCC
– P
GND
= 8V (Note 16)
P
VCC
– P
GND
= 8V
(Notes 13, 17)
MIN
TYP
40
40
100
5
1.4
140
MAX
UNITS
ns
ns
mV
μA
ms
°C
●
90
115
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:
P
VCC
internal clamp circuit self regulates to 9.4V with respect to
PGND.
Note 3:
The LTC4267-1 operates with a negative supply voltage in the
range of – 1.5V to – 57V. To avoid confusion, voltages for the PD interface
are always referred to in terms of absolute magnitude. Terms such as
“maximum negative voltage” refer to the largest negative voltage and
a “rising negative voltage” refers to a voltage that is becoming more
negative.
Note 4:
The LTC4267-1 is designed to work with two polarity protection
diode drops between the PSE and PD. Parameter ranges specified in the
Electrical Characteristics section are with respect to this product pins and
are designed to meet IEEE 802.3af specifications when these diode drops
are included. See the Application Information section.
Note 5:
Signature resistance is measured via the two-point
ΔV/ΔI
method
as defined by IEEE 802.3af. The PD signature resistance is offset from
the 25k to account for diode resistance. With two series diodes, the total
PD resistance will be between 23.75k and 26.25k and meet IEEE 802.3af
specifications. The minimum probe voltages measured at the LTC4267-1
pins are –1.5V and –2.5V. The maximum probe voltages are –8.5V and
–9.5V.
Note 6:
The PD interface includes hysteresis in the UVLO voltages to
preclude any start-up oscillation. Per IEEE 802.3af requirements, the PD
will power up from a voltage source with 20Ω series resistance on the first
trial.
Note 7:
Dynamic Supply current is higher due to the gate charge being
delivered at the switching frequency.
Note 8:
I
VPORTN_CLASS
does not include classification current
programmed at the R
CLASS
pin. Total current in classification mode will be
I
VPORTN_CLASS
+ I
CLASS
(See note 9).
Note 9:
I
CLASS
is the measured current flowing through R
CLASS
.
ΔI
CLASS
accuracy is with respect to the ideal current defined as I
CLASS
= 1.237/
R
CLASS
. The current accuracy does not include variations in R
CLASS
resistance. The total classification current for a PD also includes the IC
quiescent current (I
VPORTN_CLASS
). See Applications Information.
Note 10:
To disable the 25k signature, tie SIGDISA to V
PORTP
or hold
SIGDISA high with respect to V
PORTN
. See Applications Information.
Note 11:
The switching regulator is tested in a feedback loop that servos
V
FB
to the output of the error amplifier while maintaining I
TH
/RUN at the
midpoint of the current limit range.
Note 12:
I
POUT_LEAK
includes current drawn through P
OUT
by the power
good status circuit. This current is compensated for in the 25k signature
resistance and does not affect PD operation.
Note 13:
The LTC4267-1 PD Interface includes thermal protection. In
the event of an overtemperature condition, the PD interface will turn off
the switching regulator until the part cools below the overtemperature
limit. The LTC4267-1 is also protected against thermal damage from
incorrect classification probing by the PSE. If the LTC4267-1 exceeds the
overtemperature threshold, the classification load current is disabled.
Note 14:
The PD interface includes dual level input current limit. At turn-
on, before the P
OUT
load capacitor is charged, the PD current level is set
to a low level. After the load capacitor is charged and the P
OUT
– V
PORTN
voltage difference is below the power good threshold, the PD switches to
high level current limit. The PD stays in high level current limit until the
input voltage drops below the UVLO turn-off threshold.
Note 15:
Peak current sense voltage is reduced dependent on duty cycle
and an optional external resistor in series with the SENSE pin (R
SL
). For
details, refer to the programmable slope compensation feature in the
Applications Information section.
Note 16:
Guaranteed by design.
Note 17:
The PD interface includes overtemperature protection that is
intended to protect the device from momentary overload conditions.
Junction temperature will exceed 125°C when overtemperature protection
is active. Continuous operation above the specified maximum operating
junction temperature may impair device reliability.
42671f
4
LTC4267-1
TYPICAL PERFOR A CE CHARACTERISTICS
Input Current vs Input Voltage
25k Detection Range
Input Current vs Input Voltage
Input Current vs Input Voltage
Input Current vs Input Voltage
Power Good Output Low Voltage
vs Current
U W
Signature Resistance vs
Input Voltage
Normalized UVLO Threshold vs
Temperature
P
OUT
Leakage Current
Current Limit vs Input Voltage
42671f
5
