dm00024530

UM1063
User manual
EVALPM8803-FLY: IEEE802.3at compliant demonstration kit with
synchronous flyback converter
By Antonio Rotta
Introduction
The PM8803 is a highly integrated device embedding an IEEE802.3at-2009 compliant
powered device (PD) interface together with a PWM controller and support for auxiliary
sources. Figure 1 is an image of the EVALPM8803-FLY PoE+ demonstration board. The
same PCB can be populated with different components to support various configurations
and topologies (synchronous flyback with or without active clamp, flyback with diode
rectification).
This document focuses on a reference design for PoE+ based on flyback topology with
synchronous rectification, with the PM8803 as the main controller.
The schematics and board layout of the PoE+ converter are given in Section 2 and 3 while
the related bill of material is detailed in Section 5. In Section 7 efficiency measurements
together with main waveforms of the PoE interface and flyback converter are shown.
Figure 1. EVALPM8803-FLY demonstration kit
February 2013
DocID018573 Rev 2
1/32
www.st.com
Contents
UM1063
Contents
1
Electrical specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
2
Demonstration kit schematic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
3
Board layout . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
4
I/O connectors and test points . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
5
Bill of material . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
6
Power-up sequence . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
7
Test results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
8
2/32
7.1
Efficiency measurement with 3.3 V output . . . . . . . . . . . . . . . . . . . . . . . . 20
7.2
Efficiency measurements with 5 V output . . . . . . . . . . . . . . . . . . . . . . . . 21
7.3
Waveforms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
7.3.1
Startup sequence from PoE/PoE+ injectors . . . . . . . . . . . . . . . . . . . . . . 23
7.3.2
Transition from PoE to auxiliary and auxiliary to PoE . . . . . . . . . . . . . . 24
7.3.3
Primary side MOSFET . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
7.3.4
Secondary side MOSFET . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
7.3.5
Line transient . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
7.3.6
Load transient . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
7.3.7
Output ripple . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
DocID018573 Rev 2
UM1063
List of tables
List of tables
Table 1.
Table 2.
Table 3.
Table 4.
Table 5.
Table 6.
Table 7.
Specifications for 3.3 V output . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Specifications for 5 V output . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Connectors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
LEDs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
Test points . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
EVALPM8803-FWD BOM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Document revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
DocID018573 Rev 2
3/32
List of figures
UM1063
List of figures
Figure 1.
Figure 2.
Figure 3.
Figure 4.
Figure 5.
Figure 6.
Figure 7.
Figure 8.
Figure 9.
Figure 10.
Figure 11.
Figure 12.
Figure 13.
Figure 14.
Figure 15.
Figure 16.
Figure 17.
Figure 18.
Figure 19.
Figure 20.
Figure 21.
Figure 22.
Figure 23.
Figure 24.
Figure 25.
Figure 26.
Figure 27.
Figure 28.
Figure 29.
4/32
EVALPM8803-FLY demonstration kit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
Demonstration kit schematic: detail of the PoE+ input section
including data transformer, diode bridges, protection, and optional CM choke . . . . . . . . . . 6
Demonstration kit schematic: detail of the PoE+ section based
on flyback topology with synchronous rectification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Assembly view: top layer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Assembly view: bottom layer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Top layer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Inner layer 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Inner layer 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Bottom layer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Efficiency measurements at 48 V input . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
DC-DC only efficiency measurements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
Overall efficiency measurements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
Efficiency measurements at 48 V input . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
DC-DC only efficiency measurements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
Overall efficiency measurements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
Startup from an IEEE 802.3af injector with 2 A load. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
Startup from an IEEE 802.3at injector with 4 A load. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
Switching between PoE and auxiliary source . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
Primary side power MOSFET waveforms at 0 A load. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
Primary side power MOSFET waveforms at 4 A load. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
Details of primary side power MOSFET waveforms at 4 A load . . . . . . . . . . . . . . . . . . . . . 26
Secondary side power MOSFET waveforms at 0 A load . . . . . . . . . . . . . . . . . . . . . . . . . . 26
Secondary side power MOSFET waveforms at 4 A load . . . . . . . . . . . . . . . . . . . . . . . . . . 27
Effect of a 12 V line transient on the converter at 4 A load. . . . . . . . . . . . . . . . . . . . . . . . . 28
Effect of a 12 V line transient on the converter at 0 A load. . . . . . . . . . . . . . . . . . . . . . . . . 28
Response of the converter to a 2 A - 4 A load transient . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
Response of the converter to a 0 A - 4 A load transient . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
Output ripple measurement at 4 A . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
Output ripple measurement at 4 A with infinite persistence . . . . . . . . . . . . . . . . . . . . . . . . 30
DocID018573 Rev 2
UM1063
1
Electrical specifications
Electrical specifications
Table 1. Specifications for 3.3 V output
Parameter
Description
Min.
Input voltage range
Applied at J3 connector
Operative input voltage
Typ.
Max.
Unit
0
57
V
42
57
V
36
V
Vin rising edge
UVLO
Vin falling edge
Auxiliary input voltage range
30
V
35
Output voltage (Vout)
Vin= 42 V to 57 V, Iout 0 to Imax
3.25
Output current (Iout)
Vin= 42 V to 57 V
0
Peak-to-peak output ripple
48 Vin, Iout=Imax
3.35
20
60
V
3.45
V
6
A
30
mVpp
Inrush current limit
140
mA
DC current limit
640
mA
3.3 V efficiency DC-DC only
Vin=48 V, Iout=Imax
90
%
3.3 V overall efficiency
Vin=48 V, Iout=Imax
87
%
200
kHz
Switching frequency
Table 2. Specifications for 5 V output
Parameter
Description
Min.
Input voltage range
Applied at J3 connector
Operative input voltage
Typ.
Max.
Unit
0
57
V
42
57
V
36
V
Vin rising edge
UVLO
Vin falling edge
Auxiliary input voltage range
30
V
35
Output voltage (Vout)
Vin= 42 V to 57 V, Iout 0 to Imax
4.95
Output current (Iout)
Vin= 42 V to 57 V
0
Peak-to-peak output ripple
48Vin, Iout=Imax
5.1
20
60
V
5.25
V
4
A
30
mVpp
Inrush current limit
140
mA
DC current limit
640
mA
5 V efficiency DC-DC only
Vin=48 V, Iout=Imax
92
%
5 V overall efficiency
Vin=48 V, Iout=Imax
89
%
200
kHz
Switching frequency
DocID018573 Rev 2
5/32
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UM1063
Demonstration kit schematic
Figure 2. Demonstration kit schematic: detail of the PoE+ input section including data
transformer, diode bridges, protection, and optional CM choke
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UM1063
Demonstration kit schematic
Figure 3. Demonstration kit schematic: detail of the PoE+ section based on flyback topology with
synchronous rectification
!-V
7/32
Board layout
3
UM1063
Board layout
Board size: 10 x 16 cm. Layer copper thickness: 70 micron.
Figure 4. Assembly view: top layer
!-V
Figure 5. Assembly view: bottom layer
!-V
8/32
DocID018573 Rev 2
UM1063
Board layout
Figure 6. Top layer
!-V
Figure 7. Inner layer 1
!-V
DocID018573 Rev 2
9/32
Board layout
UM1063
Figure 8. Inner layer 2
!-V
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!-V
10/32
DocID018573 Rev 2
UM1063
4
I/O connectors and test points
I/O connectors and test points
This section provides a description of input/output connectors (Table 3), LED indicators and
commands (Table 4), as well as the available test points (Table 5).
Table 3. Connectors
Connector
J3
Label
Description
Data and power
Power and Ethernet data input port
input
J4
Data output
J2
SP
Wall adapter input. Use this input jack to connect auxiliary
source without priority in respect to PoE.
J1
SA
Wall adapter input. Use this input jack to connect auxiliary
source with priority in respect to PoE.
J5
-
Output voltage connector
-
Move the short on both jumpers at the same time:
short between pin 1 and 2 when SA auxiliary source is used
on J1 connector; short between pin 2 and 3 when SP
auxiliary source is used on J2 connector
-
Move the short on both jumpers at the same time:
short between pin 1 and 2 when SA auxiliary source is used
on J1 connector; short between pin 2 and 3 when SP
auxiliary source is used on J2 connector
JM1
JM2
Ethernet data output port
Table 4. LEDs
LED
Label
Description
D20
AUX
ON when an auxiliary source is applied to the board; proper
selection of the auxiliary source connection is done with
jumpers JM1 and JM2
D44
L1_OK
ON when T2P is asserted. This is achieved when a 2-finger
event is detected. If, after a successful PoE+ layer-1
classification, an auxiliary voltage is connected, the T2P
signal is de-asserted and the L1_OK LED is turned off.
D26
GREEN LED
ON when output voltage is present.
Table 5. Test points
Test point
Color
Description
TP1
Red
Data transformer bias voltage
TP2
Red
Positive of auxiliary source AUX 1 on J2
TP3
Black
Ground of auxiliary source AUX 1 on J2
DocID018573 Rev 2
11/32
I/O connectors and test points
UM1063
Table 5. Test points (continued)
12/32
Test point
Color
Description
TP4
Red
Input voltage VDD
TP5
Red
Secondary winding output
TP6
Red
Output voltage at J5
TP7
Red
Positive of auxiliary source AUX 2 on J1
TP8
Black
Ground of auxiliary source AUX 2 on J1
TP9
Red
Input of the primary side winding
TP10
Red
Secondary winding output
TP11
Red
VSS - I/F ground voltage
TP12
Black
Output voltage ground at J5
TP13
Red
Gate drive of the secondary side MOSFET
TP14
Red
VC supply voltage
TP15
Red
Gate drive of the primary side MOSFET (connected to
GAT1)
TP16
Red
Drain of the primary side MOSFET
TP17
Red
Gate drive of the active clamp MOSFET (connected to
GAT2)
TP18
Red
Current sense input
TP19
Black
RTN - DC-DC ground voltage
TP20
Red
L1 status indicator - referred to output voltage ground
TP21
Red
Aux present indicator - referred to output voltage ground
TP22
Red
PoE voltage after the input diode bridges
TP23
Black
Ground of the PoE voltage after the input diode bridges
TP24
Black
Chassis ground of the RJ45 connectors
DocID018573 Rev 2
Bill of material
UM1063
5
Table 6 shows the bill of material for the PoE+ section based on the PM8803 configured in flyback topology with synchronous
rectification using a gatedriver transformer.
With minimal BOM changes it is possible to switch from 3.3 V to 5 V output voltage.
Table 6. EVALPM8803-FWD BOM
3.3 V
5V
Reference
Description
Value
DocID018573 Rev 2
1
1
EVALPM8803 FLY rev1
Board PCB
8
8
C1,C2,C3,C4,C11C36,
C44,C45
Ceramic capacitor
100 nF
5
5
C5,C6,C7,C8,C30
Ceramic capacitor
10 nF
NM
NM
C9,C22
Ceramic capacitor
NM
6
6
C10,C39,C41,C48C53,
C59
Ceramic capacitor
1 µF
1
1
C12
Ceramic capacitor
NM
NM
C13,C20
3
3
NM
Tol.
Voltage
Body
Vendor
603
Std
100 V
603
TDK
1812
NM
16 V
603
Std
2.2 nF
2 kV
1812
TDK
Ceramic capacitor
NM
100 V
603
NM
C14,C16,C21
Ceramic capacitor
1 nF
100 V
603
TDK
NM
C15,C17,C24,C60
Ceramic capacitor
NM
100 V
805
NM
2
2
C18,C32
Ceramic capacitor
0.1 µF
100 V
805
TDK
2
2
C19,C38
Ceramic capacitor
22 nF
50 V
603
Std
NM
NM
C42,C46,C57,C66C69
Ceramic capacitor
NM
603
NM
1
1
C26
6
6
2
10%
20%
10%
10%
13/32
Aluminium capacitor
33 µF
20%
100 V
10x10.2
Std
C27,C33,C35,C37C67,
C68
Ceramic capacitor
10 µF
20%
6.3 V
805
Std
2
C28,C29
Ceramic capacitor
1 µF
20%
100 V
1206
TDK
1
1
C31
Ceramic capacitor
1 nF
10%
100 V
805
Std
1
1
C34
Aluminium capacitor
6.3 V
8x10.5
Suncon
330 µF
Bill of material
50 V
3.3 V
5V
Reference
Description
Value
Tol.
Voltage
Body
Vendor
DocID018573 Rev 2
NM
C40
Ceramic capacitor
NM
805
NM
NM
NM
C43
Aluminium capacitor
NM
4x6
NM
NM
NM
C47
Ceramic capacitor
NM
603
NM
1
1
C49
Ceramic capacitor
10 nF
50 V
603
Std
1
1
C50
Ceramic capacitor
100 nF
50 V
603
Std
NM
NM
C51
Ceramic capacitor
NM
1206
NM option AC
1
1
C54
Ceramic capacitor
470 pF
50 V
603
Std
1
1
C55
Ceramic capacitor
100 pF
50 V
603
Std
1
1
C56
Ceramic capacitor
22 nF
50 V
603
Std
1
1
C61
Ceramic capacitor
2.2 nF
2 kV
1812
TDK
1
1
D1, D21
STTH302S
200 V
SMC
ST
NM
NM
D2,D3,D5,D6,D15D16,
D18,D19
Zener diode
(BZX84C10)
SOT23
NM
1
1
D32
Zener diode
BZX84C10
SOT23
Std
8
8
D4,D7,D8,D9,D12D13,
D14, D17
SMA
ST
NM
NM
D10
TVS diode
NM
SMA
NM
1
1
D11
TVS diode
SMAJ58A
SMA
ST
1
1
D20
LED diode
AUX
PLCC-2
Std
NM
NM
D22
Schottky diode
(STPS15L45CB)
DPAK
NM
1
1
D23
Schottky diode
STPS1H100A
SMA
ST
NM
NM
D24,D25
Bridge rectifier
NM
SDIP
NM
1
1
D26
LED diode
PLCC-2
Std
NM
NM
D27
Zener diode
SOT23
NM
6
6
D28,D34,D36,D37D39,
D41
SOD323
ST
Std diode
Schottky diode
Schottky diode
STPS2H100A
Green LED
100 V
2.2 V
100 V
2.2 V
NM
BAT46J
100 V
UM1063
NM
Bill of material
14/32
Table 6. EVALPM8803-FWD BOM (continued)
3.3 V
5V
Reference
Description
Value
DocID018573 Rev 2
2
2
D38, D41
Schottky diode
BAT46J
NM
NM
D31,D35
Schottky diode
NM
NM
D42
Schottky diode
1
1
D44
LED diode
L1 OK
2
2
JM1,JM2
Connector
2
2
Jumper
2
2
J1,J2
1
1
J3
1
1
J4
1
1
J5
Jumper
Power jack
Tol.
Voltage
100 V
Body
Vendor
SOD323
ST option AC
NM
SOD323
NM
NM
SMA
NM
PLCC-2
Std
Jumper 3 pins male
Pitch 2.54 mm
Std
Jumper 2 pins female
Pitch 2.54 mm
Std
2.2 V
SA, SP
Std
RJ45 connector
Data and power input
Std
RJ45 connector
Data output
Std
Terminal block 2-way MOR-10X10.5-P5-2PIN
UM1063
Table 6. EVALPM8803-FWD BOM (continued)
Std
1
1
L5
SMT inductor
10 µH
MSS7341-103ML
Coilcraft
1
1
L6
SMT inductor
0.33 µH
DO1813-331ML
Coilcraft
NM
NM
L7
SMT inductor
NM
NM
Q1,Q2,Q3,Q4
MOSFET, P-ch
(IRF6216PbF)
SO8
NM
SO8
NM
NM
NM
Q5,Q6,Q7,Q8
MOSFET, N-ch
(STS4NF100)
1
1
Q12
MOSFET, N-ch
STS14N3LLH5
30 V
SO8
ST
1
1
Q14
Transistor, NPN
MMBT3904LT1
40 V
SOT23
Std
1
1
Q16
Transistor, PNP
MMBT3906LT1
40 V
SOT23
Std
1
1
Q17
MOSFET, N-ch
Si4848DY
150 V
SO8
Vishay
1
1
Q20
MOSFET, P-ch
Si2325DS
150 V
SOT23
Option AC
NM
NM
Q21
MOSFET, P-ch
IRF6216PbF
150 V
SO8
NM
4
4
R1,R2,R5,R7
Chip resistor
0
603
Std
NM
NM
R3,R4,R6,R8,R16
Chip resistor
NM
805
NM
4
4
R10,R11,R12,R13
Chip resistor
75 Ω
603
Std
NM
NM
R14,R125
Chip resistor
NM
1206
NM
Bill of material
15/32
NM
3.3 V
5V
Reference
Description
Value
1
1
R15
Chip resistor
0
2
2
R17,R43
Ferrite bead
MPZ012101A
1
1
R18
Chip resistor
NM
NM
R19,R20,R22,R25R39,
R40,R41,R42
4
4
2
Tol.
Voltage
Body
Vendor
DocID018573 Rev 2
805
Std
805
TDK
100 kΩ
1206
Std
Chip resistor
NM
603
NM
R26,R37,R49,R54
Chip resistor
0
0805
Std
2
R27,R58
Chip resistor
124 kΩ
603
Std
NM
NM
R28,R29,R30,R31R33,
R34,R35,R36R70,R71,
R100,
R120,R121
Chip resistor
NM
603
NM
2
2
R32,R51
Chip resistor
100 kΩ
805
Std
3
3
R38,R65,R117
Chip resistor
4.75 kΩ
603
Std
3
3
R44,R52,R119
Chip resistor
1 kΩ
603
Std
2
2
R45,R99
Chip resistor
47 kΩ
603
Std
1
1
R53
Chip resistor
10 Ω
805
Std
6
6
R60,R64,R68,
R84,R87,R98
Chip resistor
0
603
Std
2
2
R62,R80
Chip resistor
10 Ω
603
Std
NM
NM
R66,R81,R97
Chip resistor
NM
603
NM
2
2
R67,R106
Chip resistor
10 kΩ
603
Std
1
1
R72
Chip resistor
124 kΩ
603
Std
1
1
R73
Trimmer resistor
100 kΩ
2
2
R83,R107
Chip resistor
100 kΩ
603
Std
1
1
R89
Chip resistor
2.7 kΩ
603
Std
1
1
R90
Chip resistor
3.31 kΩ
603
Std
100 Ω,
4A
1%
1%
1%
Bill of material
16/32
Table 6. EVALPM8803-FWD BOM (continued)
Vishay
UM1063
1%
3.3 V
5V
Reference
Description
Value
Tol.
Voltage
Body
Vendor
1
1
R91
Chip resistor
10 Ω
603
Std
1
1
R92
Chip resistor
22 Ω
603
Std
1
1
R93
Chip resistor
680 Ω
603
Std
1
1
R94
Chip resistor
21 kΩ
1%
603
Std
1
1
R95
Chip resistor
24.9 kΩ
1%
603
Std
DocID018573 Rev 2
1
R96
Chip resistor
0
603
Std
NM
NM
R101
Chip resistor
NM
603
NM
1
1
R102
Chip resistor
35.6
805
Std
1
1
R103
Chip resistor
510 Ω
603
Std
1
NM
R104
Chip resistor
3.31 kΩ
1%
603
Std
NM
1
R104
Chip resistor
4.75 kΩ
1%
603
Std
2
2
R108,R109
Chip resistor
0.30 Ω
1%
1206
Std low value
1
1
R111
Chip resistor
12.4 kΩ
1%
603
Std
NM
1
R112
Chip resistor
15 kΩ
1%
603
Std
17
TP1,TP2,TP4,TP5TP6,
TP7,TP9,
TP10,TP13,TP14,TP15,
TP16,TP17,TP18,TP20,
TP21,TP22
Test points
Red
Std
Test points
Black
Std
ETH1-230LD
Coilcraft
NM
NM
17
7
7
TP3,TP8,TP11,
TP12,TP19,TP23,TP24
2
2
T1,T2
POE+ Magnetics
1%
17/32
NM
NM
T3
CM choke
NM
1
T5
Power transformer
HA3691-AL
Coilcraft
1
NM
T5
Power transformer
JA4173-AL
Coilcraft
NM
NM
T6
Power transformer
(POE300F series)
NM
Bill of material
1
UM1063
Table 6. EVALPM8803-FWD BOM (continued)
3.3 V
5V
NM
NM
Reference
Description
T7
Power transformer
Value
Tol.
Voltage
Body
Vendor
(POE13P series)
NM
DA2319-AL
Coilcraft
1
1
T8
Gate driver
transformer
1
1
U1
POE+ controller
PM8803
HTSSOP20
ST
3
3
U2,U3,U7
SMT optocoupler
Fairchild FOD817AS
4PDIP
Fairchild
1
1
U4
Shunt regulator
TS431AILT
SOT23-5
ST
NM
NM
U5
Shunt regulator
(TS2431AILT)
SOT23
NM
Bill of material
18/32
Table 6. EVALPM8803-FWD BOM (continued)
DocID018573 Rev 2
UM1063
UM1063
6
Power-up sequence
Power-up sequence
It is recommended to apply power at PoE input first, slowly increasing the voltage to verify
the absence of abnormal input current levels.
From about 2 V to about 12 V input, the demonstration kit performs the detection signature.
At 10 V input the current drawn is about 400 µA.
In the range of 14 V to 23 V, the demonstration kit performs a class-4 classification, and the
current drawn is about 40 mA.
After those two steps are verified, the voltage can be increased to 48 V typical. The PoE
converter starts operations at about 36 V input.
Three green LEDs indicate proper operation of the PoE and DC-DC section of the PM8803
demonstration kit:
Note:
•
D44 is the T2P LED and is ON when the PM8803 has successfully recognized a type 2
PSE or a 802.3at compliant injector; using a bench power supply to power up the
PM8803 demonstration board, this LED is OFF.
•
D26 indicates the presence of the output voltage.
•
D20 is the AUX LED and indicates the presence of an auxiliary voltage applied to the
converter; proper selection of the auxiliary voltage is done with jumper JM1 and JM2:
put a short between pin 1 and 2 when SA auxiliary source on J1 connector is used; put
the short between pin 2 and 3 when SP auxiliary source on J2 connector is used.
Set the R73 trimmer at a value around 10 kΩ
Adjust this value for best converter performances in terms of efficiency over its actual load
range.
Note:
In the case of SA external auxiliary source tests, it is strongly recommended to change the
position of the 100 nF, 100 V from C18, at the input filter, where it is soldered to C60, across
the internal hot-swap MOSFET. This change of position, that has no impact on the standard
compliance, permits an optimal behavior of the PM8803 device during the change of ground
reference consequent to the power jack insertion/removal.
DocID018573 Rev 2
19/32
Test results
UM1063
7
Test results
7.1
Efficiency measurement with 3.3 V output
Figure 10. Efficiency measurements at 48 V input
9RXWHIILFLHQF\#9
(IILFLHQF\>@
RYHUDOO
'&'&
,RXW>$@
!-V
Figure 11. DC-DC only efficiency measurements
9RXW'&'&RQO\HIILFLHQF\
(IILFLHQF\ >@
'&'&9
'&'&9
'&'&9
,RXW >$@
20/32
DocID018573 Rev 2
!-V
UM1063
Test results
Figure 12. Overall efficiency measurements
9RXWRYHUDOOHIILFLHQF\
(IILFLHQF\>@
RYHUDOO9
RYHUDOO9
RYHUDOO9
,RXW>$@
Efficiency measurements with 5 V output
Figure 13. Efficiency measurements at 48 V input
9RXWHIILFLHQF\#9
(IILFLHQF\>@
7.2
!-V
RYHUDOO
'&'&
,RXW>$@
!-V
DocID018573 Rev 2
21/32
Test results
UM1063
Figure 14. DC-DC only efficiency measurements
9RXW'&'&RQO\HIILFLHQF\
(IILFLHQF\>@
'&'&9
'&'&9
'&'&9
,RXW>$@
!-V
Figure 15. Overall efficiency measurements
9RXWRYHUDOOHIILFLHQF\
(IILFLHPF\>@
RYHUDOO9
RYHUDOO9
RYHUDOO9
,RXW>$@
!-V
22/32
DocID018573 Rev 2
UM1063
7.3
Test results
Waveforms
The following images were taken on a 5 V output demonstration board. Similar waveforms
are also applicable for the 3.3 V output version.
7.3.1
Startup sequence from PoE/PoE+ injectors
Figure 16. Startup from an IEEE 802.3af injector with 2 A load
Note the inrush current limited at about 140 mA and the T2P signal not asserted.
Figure 17. Startup from an IEEE 802.3at injector with 4 A load
DocID018573 Rev 2
23/32
Test results
UM1063
Note, in this case, the presence of the 2-finger during the classification phase and theT2P
signal now asserted (T2P is valid low).
7.3.2
Transition from PoE to auxiliary and auxiliary to PoE
Figure 18 shows the behavior of the PM8803 when commuting sources. The image depicts
the transition from PoE to an auxiliary source whose voltage is ~10 V lower then PoE. It can
be seen that when the auxiliary voltage is applied (SA pin goes above its threshold) the
current drawn from the PoE drops to a few milliAmps. Smooth transition occurs as can be
seen from the output voltage (blue line).
Figure 18. Switching between PoE and auxiliary source
24/32
DocID018573 Rev 2
UM1063
7.3.3
Test results
Primary side MOSFET
Figure 19. Primary side power MOSFET waveforms at 0 A load
Figure 20. Primary side power MOSFET waveforms at 4 A load
DocID018573 Rev 2
25/32
Test results
UM1063
Figure 21. Details of primary side power MOSFET waveforms at 4 A load
7.3.4
Secondary side MOSFET
Figure 22. Secondary side power MOSFET waveforms at 0 A load
26/32
DocID018573 Rev 2
UM1063
Test results
Figure 23. Secondary side power MOSFET waveforms at 4 A load
DocID018573 Rev 2
27/32
Test results
7.3.5
UM1063
Line transient
Figure 24 depicts the effect of a line transient on the PoE converter. A 12 V step on a 42 V
input PoE line (green trace) is shown. The hot-swap MOSFET (yellow trace) withstands the
transient while the input current (pink trace) is limited during the input capacitor charge; the
converter continues to work and the output voltage (blue trace) remains in regulation.
Figure 24. Effect of a 12 V line transient on the converter at 4 A load
Figure 25. Effect of a 12 V line transient on the converter at 0 A load
28/32
DocID018573 Rev 2
UM1063
7.3.6
Test results
Load transient
Figure 26. Response of the converter to a 2 A - 4 A load transient
Figure 27. Response of the converter to a 0 A - 4 A load transient
DocID018573 Rev 2
29/32
Test results
7.3.7
UM1063
Output ripple
Figure 28. Output ripple measurement at 4 A
Figure 29. Output ripple measurement at 4 A with infinite persistence
30/32
DocID018573 Rev 2
UM1063
8
Revision history
Revision history
Table 7. Document revision history
Date
Revision
Changes
23-Mar-2011
1
Initial release.
18-Feb-2013
2
Document title has been changed.
DocID018573 Rev 2
31/32
UM1063
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