LM5072
Integrated 100V Power Over Ethernet PD Interface and
PWM Controller with Aux Support
General Description
The LM5072 Powered Device (PD) interface and Pulse-
Width-Modulation (PWM) controller provides a complete
power solution, fully compliant to IEEE 802.3af, for the PD
connecting into Power over Ethernet (PoE) networks. This
controller integrates all functions necessary to implement
both a PD powered interface and DC-DC converter with a
minimum number of external components. The LM5072 pro-
vides the flexibility for the PD to also accept power from
auxiliary sources such as AC adapters in a variety of con-
figurations. The low RDS(ON) PD interface hot swap MOS-
FET and programmable DC current limit extend the range of
LM5072 applications up to twice the power level of 802.3af
compliant PD devices. The 100V maximum voltage rating
simplifies selection of the transient voltage suppressor that
protects the PD from network transients. The LM5072 in-
cludes an easy-to-use PWM controller that facilitates the
various single-ended power supply topologies including the
flyback, forward and buck. The PWM control scheme is
based on peak current mode control, which provides inher-
ent advantages including line feed-forward, cycle-by-cycle
current limit, and simplified feedback loop compensation.
Two versions of the LM5072 provide either an 80% maxi-
mum duty cycle (-80 suffix), or a 50% maximum duty cycle
(-50 suffix).
Features
PD Interface
n
Fully Compliant IEEE 802.3af PD Interface
n
Versatile Auxiliary Power Options
n
9V Minimum Auxiliary Power Operating Range
n
100V Maximum Input Voltage Rating
n
Programmable DC Current Limit Up To 800mA
n
100V, 0.7
Hot Swap MOSFET
n
Integrated PD Signature Resistor
n
Integrated PoE Input UVLO
n
Programmable Inrush Current Limit
n
PD Classification Capability
n
Power Good Indicator
n
Thermal Shutdown Protection
PWM Controller
n
Current Mode PWM Controller
n
100V Start-up Regulator
n
Error Amplifier with 2% Voltage Reference
n
Supports Isolated and Non-Isolated Applications
n
Programmable Oscillator Frequency
n
Programmable Soft-Start
n
800 mA Peak Gate Driver
n
80% Maximum Duty Cycle with Built-in Slope
Compensation (-80 device)
n
50% Maximum Duty Cycle, No Slope Compensation
(-50 device)
Applications
n
IEEE 802.3af Compliant PoE Powered Devices
n
Non-Compliant, Application Specific Devices
n
Higher Power Ethernet Powered Devices
Packages
n
TSSOP-16 EP (Exposed Pad)
Simplified Application Diagram
20184601
March 2006
LM5072
Integrated
100V
Power
Over
Ethernet
PD
Interface
and
PWM
Controller
with
Aux
Support
2006 National Semiconductor Corporation
DS201846
www.national.com
Connection Diagram
20184602
16 Lead TSSOP-EP
Ordering Information
Order Number
Description
NSC Package Type / Drawing
Supplied As
LM5072MH-50
50% Duty Cycle Limit
TSSOP-16EP/MXA16A
92 units per rail
LM5072MHX-50
50% Duty Cycle Limit
TSSOP-16EP/MXA16A
2500 units on tape and reel
LM5072MH-80
80% Duty Cycle Limit
TSSOP-16EP/MXA16A
92 units per rail
LM5072MHX-80
80% Duty Cycle Limit
TSSOP-16EP/MXA16A
2500 units on tape and reel
LM5072
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2
Pin Descriptions
Pin Number
Name
Description
1
RT
PWM controller oscillator frequency programming pin.
2
SS
Soft-start programming pin.
3
VIN
Positive supply pin for the PD interface and the internal PWM controller start-up regulator.
4
RCLASS
PD classification programming pin.
5
ICL_FAUX
Inrush current limit programming pin; also the front auxiliary power enable pin.
6
DCCL
PD interface DC current limit programming pin.
7
VEE
Negative supply pin for PD interface; connected to PoE and/or front auxiliary power return
path.
8
RTN
PWM controller power return; connected to the drain of the internal PD interface hot swap
MOSFET; should be externally connected to the reference ground of the PWM controller.
9
OUT
PWM controller gate driver output pin.
10
VCC
PWM controller start-up regulator output pin.
11
nPGOOD
PD interface Power Good indicator and delay timer pin; active low state indicates PoE
interface is in normal operation.
12
CS
PWM controller current sense input pin.
13
RAUX
Rear auxiliary power enable pin; can be programmed for auxiliary power dominance over
PoE power.
14
FB
PWM controller voltage feedback pin and inverting input of the internal error amplifier;
connect to ARTN to disable the error amplifier in isolated dc-dc converter applications.
15
COMP
Output of the internal error amplifier and control input to the PWM comparator. In isolated
applications, COMP is controlled by the secondary side error amplifier via an opto-coupler.
16
ARTN
PWM controller reference ground pin; should be shorted externally to the RTN pin as a
single point ground connection to improve noise immunity.
EP
Exposed metal pad on the underside of the device. It is recommended to connect this pad to
a PC Board plane connected to the VEE pin to improve heat dissipation.
LM5072
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Absolute Maximum Ratings
(Note 1)
If Military/Aerospace specified devices are required,
please contact the National Semiconductor Sales Office/
Distributors for availability and specifications.
VIN , RTN to VEE (Note 7)
-0.3V to 100V
RAUX to ARTN
-0.3V to 100V
ICL_FAUX to VEE
-0.3V to 100V
DCCL, RCLASS to VEE
-0.3V to 7V
nPGOOD to ARTN
-0.3V to 16V
ARTN to RTN
-0.3V to 0.3V
VCC, OUT to ARTN
-0.3V to 16V
CS, FB, RT to ARTN
-0.3V to 7V
COMP, SS to ARTN
-0.3V to 5.5V
ESD Rating
Human Body Model (Note 2)
2000V
Lead Soldering Temp. (Note 3)
Wave (4 seconds)
Infrared (10 seconds)
Vapor Phase (75 seconds)
260C
240C
219C
Storage Temperature
-55C to 150C
Junction Temperature
150C
Operating Ratings
V
IN
voltage
9V to 70V
External voltage applied to V
CC
8V to 15V
Operating Junction Temperature
-40C to 125C
Electrical Characteristics
(Note 4) Specifications in standard type face are for T
J
= +25C and those in
boldface type apply over the full operating junction temperature range. Unless otherwise specified: V
IN
= 48V, F
OSC
=
250kHz.
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
Detection and Classification
V
IN
Signature Startup Voltage
1.5
V
Signature Resistance
23.25
24.5
26
k
Signature Resistor Disengage/
Classification Engage
V
IN
Rising
11.0
12.0
12.6
V
Hysteresis
1.9
V
Classification Current Turn Off
V
IN
Rising
22
23.5
25
V
Classification Voltage
1.213
1.25
1.287
V
Supply Current During Classification
V
IN
= 17V
0.7
1.1
mA
Line Under Voltage Lock-Out
UVLO Release
V
IN
Rising
36
38.5
40
V
UVLO Lock out
V
IN
Falling
29.5
31.0
32.5
V
UVLO Hysteresis
6
V
UVLO Filter
300
s
Power Good
VDS Required for Power Good Status
1.3
1.5
1.7
V
VDS Hysteresis of Power Good Status
0.8
1.0
1.2
V
VGS Required for Power Good Status
4.5
5.5
6.5
V
Default Delay Time of Loss-of Power
Good Status
30
s
nPGOOD current Source
45
55
65
A
nPGOOD Pull Down Resistance
130
250
nPGOOD Threshold
2.3
2.5
2.7
V
Hot Swap
RDS(ON)
Hot Swap MOSFET Resistance
0.7
1.2
Hot Swap MOSFET Leakage
110
A
Default Inrush Current Limit
V
DS
= 4.0V
120
150
180
mA
Default DC Current Limit
V
DS
= 4.0V
380
440
510
mA
Front Auxiliary DC Current Limit
V
DS
= 4.0V
470
540
610
mA
Inrush Current Limit Programming
Accuracy
V
DS
= 4.0V
-15
15
%
DC Current Limit Programming Accuracy
V
DS
= 4.0V
-12
12
%
LM5072
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Electrical Characteristics
(Note 4) Specifications in standard type face are for T
J
= +25C and those in
boldface type apply over the full operating junction temperature range. Unless otherwise specified: V
IN
= 48V, F
OSC
=
250kHz. (Continued)
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
Auxiliary Power Option
ICL_FAUX Threshold
ICL_FAUX Pin Rising
8.1
8.7
9.3
V
ICL_FAUX Pull Down Current
50
A
RAUX Lower Threshold (I = 22 A)
RAUX Pin Rising
2.3
2.5
3.0
V
RAUX Upper Threshold (I = 250 A)
RAUX Pin Falling
5.4
6.0
6.9
V
RAUX Lower Threshold Hysteresis
0.8
V
RAUX Lower Threshold Current
16
22
28
A
RAUX Upper Threshold Current
187
250
313
A
VCC Regulator
VccReg
VCC Regulation (VccReg)
7.4
7.7
8
V
VCC Current Limit
15
mA
VCC UVLO (Rising)
VccReg
210
mV
VccReg
100
mV
V
VCC UVLO (Falling)
5.9
6.2
6.5
V
VIN Supply Current
V
CC
= 10V
2.0
mA
Supply Current (Icc)
V
CC
= 10V
3
mA
VCC Regulator Dropout
V
IN
V
CC
(Note 6)
6.5
V
Error Amplifier
Gain Bandwidth
3
MHz
DC Gain
67
dB
Input Voltage
1.225
1.275
V
COMP Sink Capability
5
10
mA
Current Limit
ILIM Delay to Output
30
ns
Cycle by Cycle Current Limit Threshold
Voltage
0.45
0.5
0.55
V
Leading Edge Blanking Time
65
ns
CS Sink Impedance (clocked)
35
55
Soft-start
Soft-start Current Source
8
10
12
A
Oscillator
Frequency1 (R
T
= 26.1 k
)
175
200
225
KHz
Frequency2 (R
T
= 8.7 k
)
515
580
645
KHz
Sync threshold
2.6
3.2
3.8
V
PWM Comparator
Delay to Output
25
ns
Min Duty Cycle
0
%
Max Duty Cycle (-80 Device)
75
80
85
%
Max Duty Cycle (-50 Device)
47
50
53
%
COMP to PWM Comparator Gain
0.33
COMP Open Circuit Voltage
4.3
5.2
6.1
V
COMP Short Circuit Current
0.6
1.0
1.4
mA
Slope Compensation (LM5072-80 Device Only)
Slope Comp Amplitude
70
90
110
mV
Output Section
Output High Saturation
0.25
0.75
V
LM5072
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