DEMO MANUAL DC1145B
LTC4267
Power over Ethernet Powered
Device With 12V Isolated Supply
DESCRIPTION
Demonstration circuit 1145B, featuring the LTC®4267,
provides a complete IEEE 802.3af Powered Device (PD)
interface and isolated 12V at 0.9A power supply solution
for use in Power over Ethernet (PoE) applications. An
optional connection is included for a 12V auxiliary supply
on the secondary side that disables PoE when present.
The LTC4267 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 precision dual level input cur-
PERFORMANCE SUMMARY
rent limit allows the LTC4267 to charge load capacitors
and interface with legacy PoE systems.
The LTC4267 combines the above features with a current
mode switching controller designed for driving a 6V rated
N-channel MOSFET. It features programmable slope compensation, soft-start, and constant frequency operation,
minimizing electrical noise even with light loads.
Design files for this circuit board are available at
http://www.linear.com/demo
L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks of Linear
Technology Corporation. All other trademarks are the property of their respective owners.
(TA = 25°C)
PARAMETER
CONDITIONS
Minimum Turn-on Voltage
Input from PSE, IOUT =100mA
VALUE
39V
Maximum Turn-off Voltage
Input from PSE
33V
Operating PoE Voltage
Input from PSE, IOUT = 0 to Maximum Output Current
Maximum Input Current
Input from PSE
37V to 57V
350mA
Maximum Output Current
Input from PSE, VOUT = 12V
Output Voltage
Input from PSE, IOUT = 0 to Maximum Output Current
PD Power Class
RCLASS = R7 = 45.3 Ohm
Auxiliary input voltage
Input from auxiliary supply, dominant over PSE
Invalid Signature
PD input, auxiliary supply present
0.9A
12V ±2%
Class 3, 12.95W
10V to 16V
9kΩ
OPERATING PRINCIPLES
Demonstration circuit 1145B interfaces with a customer’s
PoE test setup per Figure 1. A PSE connects to DC1145B
through RJ45 connector J1. The front end of the demo
circuit includes the required Ethernet input interface
transformer and common mode termination integrated in
J1. The LTC4267 after J1 performs IEEE 802.3af interface
functions while data is passed to connector J3 to connect
to an optional PHY. The switching regulator function is
also carried out by the LTC4267 to output an isolated 12V.
Diode bridges D2 and D6 provide the required auto-polarity
on the data pairs and spare pairs while C3 provides the
PD’s 0.1μF capacitance during detection. This demo circuit
allows detection and power classification of the PD per the
IEEE 802.3af specification. During the detection process
of a PD, the LTC4267 displays the proper 25k signature
resistor. Classification is programmed by the selection
of a single external resistor R7 connected to the RCLASS
pin. DC1145B is set for Class 3, full power PD of 12.95W
at the input.
dc1145bf
1
DEMO MANUAL DC1145B
OPERATING PRINCIPLES
After detection and classification, the PD is powered up
when the input voltage exceeds the LTC4267 turn-on undervoltage lock out (UVLO) through a dual-level current-limited
power switch. The 5μF capacitance minimum requirement
after the in-rush circuit is met with C1 and C9. While the
voltage between POUT and VPORTN is above the Power
Good trip point, the amperage through the power switch
is held below the low-level current limit. When the voltage between POUT and VPORTN is below the Power Good
trip point, the Power Good signal goes active low and the
amperage through the power switch is held below the
high level current limit.
For the PD to remain powered on, it must present to the
PSE both AC and DC components of the Maintain Power
Signature (MPS). The PD must hold the DC MPS by
drawing at least 10mA or the PSE may disconnect power.
To meet the AC MPS, the PD must present 27kΩ of AC
impedance or less. The LTC4267 will remain on with a PSE
that uses the AC disconnect method since it will always
meet the AC MPS.
The LTC4267 flyback converter operates at a typical
switching frequency of 200kHz, controlled by the current
mode controller portion of the LT4267. Galvanic isolation
is achieved through transformer T1, capacitor C14 and
opto-isolators ISO1 and ISO2.
The primary side power path is comprised of C1, L1, C9,
½ of T1, Q2, and R6. These components should be as
close to each other as possible when laying out the printed
circuit board. In an actual implementation, a snubber
circuit can be added across Q2 to reduce voltage spikes
seen at the FET. The secondary side power path is made
up of the other ½ of T1, D1, C4, C5 and C6. These parts
should also be laid out as close to each other as possible,
without overlapping any of the circuitry or traces of the
primary side.
When a 12V auxiliary supply is connected at connect J2,
which takes over as the supply for the output. ISO2 provides
an isolated signal from the auxiliary supply to disable the
LTC4267. All LTC4267 signature detection, classification
and the internal power MOSFET switch are disabled. A PSE
that uses DC disconnect will remove power. The LTC4267
can resume normal PoE operation when the auxiliary
supply is removed. If power was removed, then the PSE
will perform a new detection and then power the device.
dc1145bf
2
DEMO MANUAL DC1145B
QUICK START PROCEDURE
Demonstration circuit 1145B is easy to set up to evaluate
the performance of the LTC4267. For proper equipment
setup, refer to Figure 1 and follow the procedure below:
1. Apply an initial load of 100mA at VOUT.
2. Connect a PoE compliant Power Sourcing Equipment
(PSE) to RJ45 connector J1.
3. The PSE will detect and power up the PD. Verify output
voltage measures 12V.
4. If the PSE has status readout, verify the proper PD
power class 3 was detected.
5. In place of a PSE, the DC1145 board can be powered
by an alternate input power supply. Connect 48V
through the PoE+ and PoE– terminals. Only one set of
connections is necessary. Do not connect more than
one power source.
6. Increase the load at VOUT up to 0.9A. Observe the
output regulation, ripple voltage, efficiency and other
parameters
7. Measure PWRGD and SIGDISA relative to POE–. Verify
PWRGD is logic low and SIGDISA is logic low.
8. Connect a 12V auxiliary supply and verify VOUT equals
the new supply.
9. Measure PWRGD and SIGDISA relative to POE–. Verify
PWRGD is logic high and SIGDISA is logic high.
10. Remove the 12V auxiliary supply and verify the PSE
power returns.
+
V
RJ45
–
+
+
–
A
LOAD
–
RJ45
PSE
CAT5
CABLE
Figure 1. DC1145B Test Setup
dc1145bf
3
DEMO MANUAL DC1145B
MEASURED DATA
Figure 2 and 3 are measured data for a typical DC1145B.
86
84
Efficiency (%)
82
80
78
Vin=37V
76
Vin=48V
74
Vin=57V
72
70
0
0.2
0.4
0.6
0.8
1
Output Current (A)
Figure 2: Efficiency (Input Voltage (VIN) is measured at RJ45 Jack)
12.05
12.04
Output Voltage (V)
12.03
12.02
12.01
12
Vin=37V
11.99
Vin=48V
11.98
Vin=57V
11.97
11.96
11.95
0
0.2
0.4
0.6
0.8
1
Output Current (A)
Figure 3: Output Voltage Regulation
dc1145bf
4
DEMO MANUAL DC1145B
PARTS LIST
ITEM
QTY
REFERENCE
PART DESCRIPTION
MANUFACTURER/PART NUMBER
Required Circuit Components
1
1
C1
Cap., Elec. 4.7μF 63V 20%
PANASONIC, EEEFK1J4R7R
2
1
C2
Cap., NPO 680pF 50V 10% 0805
AVX, 08055A681KAT2A
3
1
C3
Cap., X5R 0.1μF 100V 20% 1206
Taiyo Yuden, HMK316BJ104ML-T
4
2
C4, C5
Cap., Tant. 47μF 20V 20% 7343
Kemet, T495D476K020ATE100
5
1
C6
Cap., X5R 10μF 16V 20% 1206
Taiyo Yuden, EMK316BJ106ML
6
1
C8
Cap., X5R 4.7μF 16V 20% 0805
Taiyo Yuden, EMK212BJ475MG
7
1
C9
Cap., X7R 1μF 100V 20% 1210
TDK, C3225X7R2A105M
8
1
C10
Cap., X7R 0.01μF 25V 10% 0805
Kemet, C0805C103K3RACTU
9
2
C11, C16
Cap., X7R 0.01μF 25V 10% 0603
Kemet, C0603C103K3RACTU
10
1
C13
Cap., X7R 0.033μF 50V 20% 0603
AVX, 06035C333MAT2A
11
1
C14
Cap., X7R 2200pF 250V 10% 1812
Murata, GA343QR7GD222KW01L
12
1
C17
Cap., X7R 0.47μF 16V 20% 0805
AVX, 0805YC474KAT2A
13
1
D1
Diode, Schottky 3A 60V PowerDi5
Diodes Inc., PDS360-13
14
2
D2, D6
Rect Bridge GP 100V/0.8A PbF
Diodes Inc., HD01-T
15
2
D3, D7
Diode, High Speed
Philips Semi., BAS516
16
2
D4, D8
Diode, Zener 8.2V 200MW SOD-323
Diodes Inc., MMSZ5237BS-7-F
17
1
D5
Diode, Schottky 2A 20V SMA
Diodes Inc., B220A-13-F
18
1
D9
Voltage Supressor, 58V
Diodes Inc., SMAJ58A-13-F
19
3
D11, D12, D13
Diode, SWITCH 75V 200MW SOD323
Diodes Inc., 1N4148WS-7-F
20
1
ISO1
Opto Iso., NEC High Ctr. PbF
NEC, PS2911-1-K-A
21
1
ISO2
Opto Iso., 4PIN MFLAT SINGLE DC HIGH V COUPLER
NEC, PS2913-1-K-A
22
1
L1
Inductor, 8.2μH DO1608C
COILCRAFT, DO1608C-822ML
23
1
Q1
XSTR, High Voltage PbF SOT23
ON Semi., MMBTA42LT1G
24
1
Q2
MOSFET, N-Chan., 200V SUPERSOT(6LEADS)
Fairchild Semi., FDC2612
25
1
R1
Res., Chip 13 0.1W 5% 0805
Vishay CRCW080513R0JNEA
26
2
R2, R3
Res., Chip 220k 0.1W 5% 0805
Vishay, CRCW0805220KJNEA
27
1
R4
Res., Chip 150 0.1W 5% 0603
Vishay, CRCW0603150RJNEA
28
1
R5
Res., Chip 10k 0.1W 5% 0603
Vishay, CRCW060310K0JNEA
29
1
R6
Res 0.05 OHM 1/4W 1% 1206 SMD
Vishay, WSL1206R0500FEA
30
1
R7
Res, Chip 45.3 0.06W 1% 0603
Vishay, CRCW060345R3FKEA
31
1
R8
Res., Chip 1k 0.06W 5% 0603
Vishay, CRCW06031K00JNEA
32
1
R9
Res., Chip 7.5k 0.1W 5% 0603
Vishay, CRCW06037K50JNEA
33
1
R10
Res., Chip 402 0.1W 1% 0603
Vishay, CRCW0603402RFKEA
34
1
R11
Res., Chip 6.8K 0.1W 5% 0603
Vishay, CRCW06036K80JNEA
35
1
R12
Res., Chip 107k 0.1W 1% 0603
Vishay, CRCW0603107KFKEA
36
1
R13
Res., Chip 200k 0.1W 5% 0603
Vishay, CRCW0603200KJNEA
37
1
R14
Res., Chip 61.9k 0.06W 1% 0603
Vishay CRCW060361K9FKEA
38
1
R15
Res., Chip 28.0k 0.1W 1% 0603
Vishay, CRCW060328K0FKEA
39
1
R16
Res., Chip 100k 0.1W 5% 0603
Vishay, CRCW0603100KJNEA
40
1
R19
Res., Chip 300k 0.1W 5% 0603
Vishay, CRCW0603300KJNEA
dc1145bf
5
DEMO MANUAL DC1145B
PARTS LIST
41
1
R20
Res., Chip 100 0.1W 5% 0603
Vishay, CRCW0603100RJNEA
42
1
T1
Transformer, PoE
Pulse, PA1138NL
43
1
U1
I.C., PoE Switching Reg. DFN(16)(DHC)5mm × 3mm
Linear Tech.Corp.LTC4267CDHC#PBF
44
1
U2
I.C., Prog. Reference SO8NB
Linear Tech. Corp., LT1431CS8#PBF
Additional Demo Board Circuit Components
1
0
C7, C12 (Opt)
Cap., 0603
2
0
C15 (Opt)
Cap., 1206
3
0
J3 (Opt)
Headers, Dbl. Row 2mm Ctrs.
4
0
R18 (OPT)
Res., 1206
CommConn Con Inc., 2202S-06G2
Hardware for Demo Board Only
1
1
D10
LED, GRN
Panasonic, LN1351CTR
2
8
E1, E2, E3, E4, E5, E6, E7, E8
Turret, Testpoint
Mill Max, 2501-2-00-80-00-00-07-0
3
1
J1
Pulse Jack, PowerJack T12
Pulse Engrng., JK0-0044NL
4
1
J2
Connector, Wall Adapter
Cui Inc., PJ-002AH
5
4
MH1, MH2, MH3, MH4
STAND-OFF, NYLON 0.25" tall
KEYSTONE, 8831(SNAP ON)
6
1
R17
7
1
Res., Chip 2k 0.06W 5% 0603
Vishay CRCW06032K00JNEA
FAB, 1145B_Rev1
DEMO CIRCUIT 1145B
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Information furnished by Linear Technology Corporation is believed to be accurate and reliable.
However, no responsibility is assumed for its use. Linear Technology Corporation makes no representation that the interconnection of its circuits as described herein will not infringe on existing patent rights.
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DEMO MANUAL DC1145B
SCHEMATIC DIAGRAM
dc1145bf
7
DEMO MANUAL DC1145B
DEMONSTRATION BOARD IMPORTANT NOTICE
Linear Technology Corporation (LTC) provides the enclosed product(s) under the following AS IS conditions:
This demonstration board (DEMO BOARD) kit being sold or provided by Linear Technology is intended for use for ENGINEERING DEVELOPMENT
OR EVALUATION PURPOSES ONLY and is not provided by LTC for commercial use. As such, the DEMO BOARD herein may not be complete
in terms of required design-, marketing-, and/or manufacturing-related protective considerations, including but not limited to product safety
measures typically found in finished commercial goods. As a prototype, this product does not fall within the scope of the European Union
directive on electromagnetic compatibility and therefore may or may not meet the technical requirements of the directive, or other regulations.
If this evaluation kit does not meet the specifications recited in the DEMO BOARD manual the kit may be returned within 30 days from the date
of delivery for a full refund. THE FOREGOING WARRANTY IS THE EXCLUSIVE WARRANTY MADE BY THE SELLER TO BUYER AND IS IN LIEU
OF ALL OTHER WARRANTIES, EXPRESSED, IMPLIED, OR STATUTORY, INCLUDING ANY WARRANTY OF MERCHANTABILITY OR FITNESS
FOR ANY PARTICULAR PURPOSE. EXCEPT TO THE EXTENT OF THIS INDEMNITY, NEITHER PARTY SHALL BE LIABLE TO THE OTHER FOR
ANY INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES.
The user assumes all responsibility and liability for proper and safe handling of the goods. Further, the user releases LTC from all claims
arising from the handling or use of the goods. Due to the open construction of the product, it is the user’s responsibility to take any and all
appropriate precautions with regard to electrostatic discharge. Also be aware that the products herein may not be regulatory compliant or
agency certified (FCC, UL, CE, etc.).
No License is granted under any patent right or other intellectual property whatsoever. LTC assumes no liability for applications assistance,
customer product design, software performance, or infringement of patents or any other intellectual property rights of any kind.
LTC currently services a variety of customers for products around the world, and therefore this transaction is not exclusive.
Please read the DEMO BOARD manual prior to handling the product. Persons handling this product must have electronics training and
observe good laboratory practice standards. Common sense is encouraged.
This notice contains important safety information about temperatures and voltages. For further safety concerns, please contact a LTC application engineer.
Mailing Address:
Linear Technology
1630 McCarthy Blvd.
Milpitas, CA 95035
Copyright © 2004, Linear Technology Corporation
dc1145bf
8
Linear Technology Corporation
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