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Maxim > Design support > App notes > Basestations/Wireless Infrastructure > APP 5043 Maxim > Design support > App notes > Hot-Swap and Power Switching Circuits > APP 5043 Maxim > Design support > App notes > Power-Supply Circuits > APP 5043 Keywords: powered device, PD, Power over Ethernet, PoE, IEEE 802.3af, IEEE 802.3at, Class 2 PD, Class 3 PD, IP phones, IP cameras, security camera, WAP, Wireless Access Point, Point of Sales, POS, Thin Client, Ethernet repeater, active clamped forward, flyback REFERENCE DESIGN 5043 INCLUDES:
Tested circuit
Schematic
BOM
Apr 28, 2011
Active-Clamped Forward, Dual-Output PD Provides High-Performance Solution for PoE Applications Abstract: This reference design is for a highly efficient, active-clamped forward, dual 3.3V/8.8Voutput powered device (PD). The design features the MAX5969A and MAX5900 as its controllers. The design also uses the MAX5974C, which controls current-mode PWM converters and provides zero-voltage switching (ZVS) and frequency foldback to enhance supply efficiency. Using these devices, this RD is IEEE® 802.3at compliant and is a high-performance, compact, and cost-efficient solution for PoE and nonstandard high-power PDs. The design can also support the auxiliary input voltage to provide maximum 55W output power.
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General Description The design features the MAX5969A, MAX5900, and MAX5974C. The MAX5969A is compliant with the IEEE 802.3at standard in a power-over-Ethernet (PoE) system. The device can also get power from a wall adapter (WAD). The MAX5900 hot-swap controller smoothly enables a nonstandard high power from a nonstandard Power Sourcing Equipment (PSE). The MAX5974C provides control for wide-input-voltage, ZVS active-clamped, current-mode PWM converters and frequency foldback for PoE and high-power applications. Using these devices, this reference design is IEEE 802.3at compliant. It is also a high-performance, compact, and cost-effective solution for a nonstandard high power PD.
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Specifications The 3.3V/3.35A and 8.8V/4.6A PD is designed to meet the following specifications: Input voltage: 42V to 57V Nonstandard PSE: 37V to 57V WAD input voltage: 30V up to 57V VOUT1 : 3.3V/3.35A VOUT2 : 8.8V/4.6A Output ripples: ±1% Line and load regulation: 3.3V = ±0.2%, 8.8V = ±2% Total efficiency with loads of 3A at 3.3V, 4.2A at 8.8V, and 48V input: 90.4% (including input LAN transformer and MOSFET bridge)
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Top view of the reference design.
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A
B
C
1
J1
TX4-P8
TX4+P7
TX3-P5
TX3+P4
TX2-P6
TX2+P3
TX1-P2
8 7 6 5 4 3 2 1
21
DATA OUT
TX1+P1
J2
G1
17
G2
TRCT4
TRCT3
TRCT2
TRCT1
18
TD1+ TC1 TD1VC1 TD2+ TC2 TD2VC2 TD3+ TC3 TD3VC3 TD4+ CT TD4VC4
22
Y1
19
Y2
20
75
R70
75
R69
75
R68
75
R67
11 12 10 13 4 6 5 14 3 1 2 15 8 7 9 16
C39 1000pF
TRCT3
CHASSIS GND
TRCT2
TRCT1
250VAC
G1
D
G2
2
G1
D
G2
S2 S1
N5
1
D11 1
D7 5.1V
D24
EN\
Q5
R5 1M
Q1
D39 15V
D40 15V
D35 D22 D30
D28
D34
D18 5.1V
D19 1
N7 DUAL N-CHANNEL MOSTFET
D14 5.1V
D15 1
D2
D1 5.1V 3 2 2 3
EN\
Q7
R24 1M
Q3
R11 499k
R1 499k
R27 499k
R3 499k
1
D16 5.1V
D17 1
D6
D3 5.1V
D20 5.1V
D21 1
D13 1
D12 5.1V
3 2 2 Q6
Q2
3
3
D27
3
D
2
S2 S1
3 2
2 3
3 2 2 Q8
Q4
EN\
G1
D
G2
R2 499k
D29
3
S2 EN\
G1
D
G2
R4 499k
R22 499k
S1
1
R28 499k
N6
S2 S1
TRCT4
DATA & POWER IN
N8
SMBJ58A
-48V
GND
Open
D36
VSS
NC
NC
DET
VDD
U1
R62 3.01k
Open
C31
-48V
5
4
3
2
R50 24.9k 1
-48V
0.1uF
D26 C29
GND
4
Open
C36
EN\ D37
R56 29.4k
R44 30.9
RTN
WAD
PG
2EC
CLS
-48V
MAX5969A
4
4 3 2 1
10
R63
GATE
DRAIN
5 6 7 8
R66 24.9k RTN
-48VOUT
HP\
U7
C33
R45 20k
5
RTN
R58 10k HP-SEC\
3.3V/3.5A
499k
R52
D32
R51 100k
OPTO1
PGOOD\
R61 10k
Q9
R65 24.9k
R60 0 WAD_S
-48V
3.3V/3.5A
EN\
R57 1M
GND
OPTO1
U9
OPTO1
PGOOD
C30 0.1uF
WAD
FDS86141
N11
MAX5900
VEE
ON/OFF
PG
EC\
GND
U6
6
7
8
9
10
U8
49.9k
R59
5
C35
4
2 3
D ate:
Size
Title
0.1uF
1
AT\
R55 20k
Q10
R49 10k
RTN
60W
H X
N umber
V-
C32 Open
PG
RTN
-48VOUT
PG
3.3V/3.5A
V+
6
Ext. PSU
R evision
Ceragon Midspan
PoE 802.3at
PWR SOURCES
Ext. PSU
Ceragon Midspan
PoE 802.3at
PWR SOURCES
MAX5969-MAX5900-MAX5974_3.3V_8V_60W
60W
25.5W
PWR LEVELS
L
L
WAD
PRIMARY POWER LEVEL SIGNALS
60W
60W
25.5W
PWR LEVELS
L
H
HP
H
L
L
WAD_S L
X
20k
R54
R53 10k
OPTO1
U5
R64 0
SECONDARY POWER LEVEL SIGNALS
H
HP-SEC
FDS89141 6 5 PGOOD\
8 7 N10
WAD-IN-
EC\
R47 100k
3.3V/3.5A
NOTES: AT\ Active Low to Detect PSE 802.3at Present WAD-IN+
0.1uF
0.1uF
C34
GND
6
A
B
C
D
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A
B
1
R29 200k
0
R16
14.7k
2
-48VOUT
V-
2
1
C16
FB
2200pF
C18
FOD817CSD
R31 4.99k U3
2k
R10
PG
EN
C15 47nF
FB
1
100k
C40 0.1uF
VC
R33 301
Open 4
C19
10
R19
R26
R20 10k
2k
R42
4.02k
R34
0
R46
4.02k
R18
499 C24 330pF
Open
C22
9
47nF
RTN
3
C20 68nF
-48VOUT
C5
D8
-48VOUT
10
11
22V 12
D38
33uF
+ C7 100uF
1uF
-48VOUT
D9
D10
0.1uF C6
3.3mH
L1
C37
3
TLV431AIDBVT-1.24V
U4
CS
PGND
CSSC
Q11
C4
NDRV
VC AUXDRV
100k
R9
R71
SGND
MAX5974C
FFB COMP
RT
R32 1k
VC
4
3
R8 30.1k
PG
30.1k
R14
+
GND
DCLMP
DITHER/SYNC
SS DT
4.7nF
U2
R17 Open
C23 Open
R30 100k
10nF
R15
FB
C14
0.1uF
16.9k
R6
C3
499
R7 16 5
C
V+
15 6
2
14 7
4
2
3
1
6
5
5 6 7 8
R21 0.1
C21 Open
7
8
9
N4
11
10
12
RTN1
R37 Open
10
R23
N3
T1
SHORT
R36 2.49k C38
R35 4.12k
-48VOUT
R25 0.1
4 3 2 1
13 8 3 5
C17 10nF
10
R39
4
4
7 8
5 6
FDS6930B
N1
1
3 2
4
R40 10
D5
OPEN
R13 10
D31 OPEN
1 2 3 4
N9
OPTION1
FDMC7696
10
OPEN
D23 R38
OPEN
R38B
8 N14 7 6 5
3.3V/3.5A
Si1411DH
3
D
1
2 3
5 6 2 1 4
5 6 7 8 4 3 2 1
R41 Open
OPen
C1
OPEN
5
C13
R12 10
L3
5
Date:
Size
RTN1
C11
C12
RTN
0.1uF
RTN
3.3V/3.5A
6
6
MAX5969-MAX5900-MAX5974_3.3V_8V_60W
RTN
RTN1
3.3V/3.5A
3.3V/3.5A
22uF
N umber
C10 22uF
C9
Title
D33 C8 OPEN 220uF
RTN1
D25
C28 0.1uF
RTN1
47uF
47uF
Open
Open R48 Open
4
T2
Wurth: 744 7798 360
RTN
8
1
OPEN
C27
8.8V/4.7A
8.8V/4.7A
8.8V/4.7A
C26
OPTION2
47uF
47uF
R43 Open
C25
C2
D4
FDMC86324
L2
CDRH127/LD-150MC
5
R evi si on
A
B
C
D
IEEE is a registered service mark of the Institute of Electrical and Electronics Engineers, Inc.
Related Parts MAX5900 MAX5969A MAX5974C
-100V, SOT23/TDFN, Simple Swapper Hot-Swap Controllers IEEE 802.3af/at-Compliant, Powered Device Interface Controllers with Integrated Power MOSFET Active-Clamped, Spread-Spectrum, Current-Mode PWM Controllers
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