dm00024451

UM1062
User manual
EVALPM8803-FWD: IEEE802.3at compliant demonstration kit
with synchronous active clamp forward converter
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-FWD PoE+ demonstration board. The
same PCB can be populated with different components to support various configurations
and options (active clamp forward both with synchronous rectification or with diode
rectification).
This document focuses on a reference design for PoE+ based on AC forward topology with
synchronous rectification, with the PM8803 as the main controller.
The schematics and board layout of the PoE+ section 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 AC forward converter are shown.
Figure 1.
March 2011
EVALPM8803-FWD demonstration kit
Doc ID 018571 Rev 1
1/31
www.st.com
Contents
UM1062
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
2/31
7.1
Efficiency measurement with 3.3 V output . . . . . . . . . . . . . . . . . . . . . . . . 20
7.2
Efficiency measurement 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 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
7.3.6
Load transient . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
7.3.7
Output ripple . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
Doc ID 018571 Rev 1
UM1062
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 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
Doc ID 018571 Rev 1
3/31
List of figures
UM1062
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.
4/31
EVALPM8803-FWD 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 AC forward 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 at different input voltages. . . . . . . . . . . . . . . . . . . . 20
Overall efficiency measurements at different input voltages. . . . . . . . . . . . . . . . . . . . . . . . 21
Efficiency measurements at 48 V input . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
DC-DC only efficiency measurements at different input voltages. . . . . . . . . . . . . . . . . . . . 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
Secondary side power MOSFET waveforms at 0 A load . . . . . . . . . . . . . . . . . . . . . . . . . . 26
Secondary side power MOSFET waveforms at 4 A load . . . . . . . . . . . . . . . . . . . . . . . . . . 26
Effect of a 12 V line transient on the converter at 4 A load. . . . . . . . . . . . . . . . . . . . . . . . . 27
Effect of a 12 V line transient on the converter at 0 A load. . . . . . . . . . . . . . . . . . . . . . . . . 27
Response of the converter to a 2 A - 4 A load transient . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
Response of the converter to a 0 A - 4 A load transient . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
5 V output ripple measurement at 4 A . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
5 V output ripple measurement at 4 A with infinite persistence . . . . . . . . . . . . . . . . . . . . . 29
Doc ID 018571 Rev 1
UM1062
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
30
60
V
3.45
V
6
A
40
mVpp
Inrush current limit
140
mA
DC current limit
640
mA
3.3 V efficiency DC-DC only
Vin=48 V, Iout=Imax
92
%
3.3 V overall efficiency
Vin=48 V, Iout=Imax
89
%
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
30
60
V
5.25
V
4
A
40
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
Doc ID 018571 Rev 1
5/31
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Demonstration kit schematic
UM1062
2
Demonstration kit schematic
Figure 2.
Demonstration kit schematic: detail of the PoE+ input section including data
transformer, diode bridges, protection, and optional CM choke
!-V
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Figure 3.
UM1062
Demonstration kit schematic
Demonstration kit schematic: detail of the PoE+ section based on AC forward
topology with synchronous rectification
!-V
7/31
Board layout
3
UM1062
Board layout
Board size: 6 x 16 cm. Layer copper thickness: 70 micron.
Figure 4.
Assembly view: top layer
!-V
Figure 5.
Assembly view: bottom layer
!-V
8/31
Doc ID 018571 Rev 1
UM1062
Figure 6.
Board layout
Top layer
!-V
Figure 7.
Inner layer 1
!-V
Doc ID 018571 Rev 1
9/31
Board layout
Figure 8.
UM1062
Inner layer 2
!-V
Figure 9.
Bottom layer
!-V
10/31
Doc ID 018571 Rev 1
UM1062
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
Label
Description
Data and power
Power and Ethernet data input port
input
J3
J4
Data output
J2
SP
Wall adapter input. Use this input jack to connect auxiliary
source without priority of the auxiliary source wrt PoE.
J1
SA
Wall adapter input. Use this input jack to connect auxiliary
source with priority of the auxiliary source wrt 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
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
JM1
JM2
Table 4.
Table 5.
Ethernet data output port
LEDs
ON when output voltage is present.
Test points
Test point
Color
Description
TP1
Red
Data transformer bias voltage
TP2
Red
Positive of auxiliary source AUX 1 on J2
TP3
Black
Auxiliary source AUX 1 ground on J2
TP4
Red
Input voltage VDD
TP5
Red
Secondary winding output
TP6
Red
Output voltage on J5
Doc ID 018571 Rev 1
11/31
I/O connectors and test points
Table 5.
12/31
UM1062
Test points (continued)
Test point
Color
Description
TP7
Red
Positive of auxiliary source AUX 2 on J1
TP8
Black
Auxiliary source AUX 2 ground 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
TP13
Red
Gate drive of the secondary side MOSFET
TP14
Red
VC supply voltage
TP15
Red
Gate drive of the primary side MOSFET
TP16
Red
Drain of the primary side MOSFET
TP17
Red
Gate drive of the 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
TP26
Red
Gate drive of the secondary side MOSFET
Doc ID 018571 Rev 1
Bill of material
Bill of material
13/31
5
With minimal BOM changes it is possible to switch from 3.3 V to 5 V output voltage.
Table 6.
EVALPM8803-FWD BOM
Doc ID 018571 Rev 1
3.3 V
5V
Reference
Description
Value
1
1
EVALPM8803-FWD
ACFWD rev1
Board PCB
7
7
C1,C2,C3,C4,C11C36,
C57
Ceramic capacitor
100 nF
4
4
C5,C6,C7,C8
Ceramic capacitor
10 nF
NM
NM
C9,C22
Ceramic capacitor
NM
6
6
C10,C39,C41,
C48,C53,C59
Ceramic capacitor
1 µF
1
1
C12
Ceramic capacitor
NM
NM
C13,C20
3
3
NM
Tol.
Body
Vendor
50 V
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,C56,C66C69
Ceramic capacitor
NM
603
NM
1
1
C26
Aluminium capacitor
33 µF
20%
100 V
10x10.2
Std
2
2
C33,C35
Ceramic capacitor
10 µF
20%
6.3 V
805
Std
2
2
C28,C29
Ceramic capacitor
1 µF
20%
100 V
1206
TDK
2
2
C31,C37
Ceramic capacitor
1 nF
10%
100 V
805
Std
1
1
C34
Aluminium capacitor
330 µF
6.3 V
8x10.5
Suncon
NM
NM
C40
Ceramic capacitor
NM
805
NM
NM
NM
C43
Aluminium capacitor
NM
4x6
NM
10%
20%
10%
10%
UM1062
Voltage
EVALPM8803-FWD BOM (continued)
3.3 V
5V
Reference
Description
Value
NM
NM
C47
Ceramic capacitor
NM
1
1
C49
Ceramic capacitor
22 nF
1
1
C50
Ceramic capacitor
1
1
C51
1
1
1
Tol.
Voltage
Doc ID 018571 Rev 1
Vendor
603
NM
50 V
603
Std
100 nF
50 V
603
Std
Ceramic capacitor
47 nF
200 V
1206
Syfer
C54
Ceramic capacitor
470 pF
50 V
603
Std
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
Std diode
STTH302S
200 V
SMC
STMicroelectronics
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
Schottky diode
STPS2H100A
SMA
STMicroelectronics
NM
NM
D10
TVS diode
NM
SMA
NM
1
1
D11
TVS diode
SMAJ58A
SMA
STMicroelectronics
1
1
D20
LED diode
AUX
PLCC-2
Std
NM
NM
D22,D23
Schottky diode
NM
Dpak
Option diode rect.
NM
NM
D24,D25
Bridge rectifier
NM
SDIP
NM
1
1
D26
LED diode
Green LED
PLCC-2
Std
NM
NM
D27
Zener diode
NM
SOT23
NM
9
9
D28,D29,D30,
D31D37,D38, D39,
D40D41
Schottky diode
BAT46J
SOD323
STMicroelectronics
NM
NM
D42
Schottky diode
NM
SMA
NM
1
1
D44
LED diode
L1 OK
PLCC-2
Std
100 V
2.2 V
2.2 V
100 V
2.2 V
Bill of material
14/31
Body
UM1062
Table 6.
EVALPM8803-FWD BOM (continued)
Doc ID 018571 Rev 1
5V
Reference
Description
Value
Tol.
Voltage
Body
Vendor
2
2
JM1,JM2
Connector
Jumper 3 pins male
Pitch 2.54 mm
Std
2
2
Jumper
Jumper 2 pins female
Pitch 2.54 mm
Std
2
2
J1, J2
Power jack
SA, SP
Std
1
1
J3
RJ45 connector
Data and power input
Std
1
1
J4
RJ45 connector
Data output
Std
1
1
J5
Terminal block 2-way
MOR-10X10.5-P5-2PIN
Std
1
1
L2
SMT inductor
1 mH
LPS4018-105ML
Coilcraft
NM
1
L3
SMT inductor
10 µH
SER1360-103KL
Coilcraft
1
NM
L3
SMT inductor
6 µH
SER1360-602KL
Coilcraft
1
1
L5
SMT inductor
10 µH
MSS7341-103ML
Coilcraft
NM
NM
Q1,Q2,Q3,Q4
MOSFET, P-ch
IRF6216PbF
100 V
SO8
IR
NM
NM
Q5,Q6,Q7,Q8
MOSFET, N-ch
STS4NF100
100 V
SO8
STMicroelectronics
2
2
Q11,Q12
MOSFET, N-ch
STS14N3LLH5
30 V
SO8
STMicroelectronics
1
1
Q14
Transistor, NPN
MMBT3904LT1
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
Vishay
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
1
1
R15
Chip resistor
0
805
Std
2
2
R17,R43
Ferrite bead
MPZ012101A
805
TDK
4
4
R26,R37,R49,R54
Chip resistor
0
805
Std
100 Ω,
4A
UM1062
3.3 V
Bill of material
15/31
Table 6.
EVALPM8803-FWD BOM (continued)
3.3 V
5V
Reference
Description
Value
NM
NM
R19,R20,R22,R25R39,
R40,R41,R42
Chip resistor
NM
2
2
R27,R58
Chip resistor
124 kΩ
NM
NM
R28,R29,R30,R31R33,
R34,R35,R36R70,R100
,R104,
R120,R121
Chip resistor
2
2
R32,R51
3
3
3
Tol.
Doc ID 018571 Rev 1
Vendor
603
NM
603
Std
NM
603
NM
Chip resistor
100 kΩ
805
Std
R38,R65,R117
Chip resistor
4.75 kΩ
603
Std
3
R44,R52,R119
Chip resistor
1 kΩ
603
Std
2
2
R45,R99
Chip resistor
47 kΩ
603
Std
2
2
R53,R59
Chip resistor
10 Ω
805
Std
2
2
R57,R60
Chip resistor
5.6 Ω
805
Std
1
1
R62
Chip resistor
10 Ω
603
Std
3
3
R64,R68,R98
Chip resistor
0
603
Std
NM
NM
R66,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
NM
NM
R79,R86
Chip resistor
NM
805
NM
1
1
R89
Chip resistor
2.7 kΩ
603
Std
1
1
R90
Chip resistor
680 Ω
603
Std
1
1
R91
Chip resistor
10 Ω
603
Std
1
1
R92
Chip resistor
22 Ω
603
Std
1
NM
R93
Chip resistor
680 Ω
603
Std
NM
1
R93
Chip resistor
820 Ω
603
Std
1%
1%
Vishay
Bill of material
16/31
Body
1%
Voltage
UM1062
Table 6.
EVALPM8803-FWD BOM (continued)
3.3 V
5V
Reference
Description
Value
Tol.
1
1
R94
Chip resistor
21 kΩ
1
1
R95
Chip resistor
24.9 kΩ
1
1
R96
Chip resistor
NM
NM
R101
1
1
Doc ID 018571 Rev 1
Vendor
1%
603
Std
1%
603
Std
0
603
Std
Chip resistor
NM
603
NM
R102
Chip resistor
35.7 Ω
805
Std
1
1
R103
Chip resistor
510 Ω
603
Std
1
1
R104
Chip resistor
4.75 kΩ
603
Std
1
1
R107
Chip resistor
100 kΩ
603
Std
2
2
R108,R109
Chip resistor
0.30 Ω
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
18
18
TP1,TP2,TP4,TP5TP6,
TP7,TP9,
TP10,TP13,TP14,TP15,
TP16,TP17,TP18,TP20,
TP21,TP22,TP26
Test points
Red
Std
7
7
TP3,TP8,TP11,
TP12,TP19,TP23,TP24
Test points
Black
std
2
2
T1,T2
PoE+ magnetics
ETH1-230LD
Coilcraft
NM
NM
T3
CM choke
NM
NM
NM
1
T5
Power transformer
HA3691-AL
Coilcraft
1
NM
T5
Power transformer
JA4173-AL
Coilcraft
NM
NM
T6
Power transformer
(PoE300F)
NM
NM
NM
T7
Power transformer
(PoE13P)
NM
1
1
U1
PoE+ controller
PM8803
HTSSOP20
STMicroelectronics
3
3
U2,U3,U7
SMT optocoupler
Fairchild FOD817AS
4PDIP
Fairchild
1%
UM1062
Body
1%
Voltage
Bill of material
17/31
Table 6.
EVALPM8803-FWD BOM (continued)
3.3 V
5V
Reference
Description
Value
1
1
U4
Shunt regulator
NM
NM
U5
Shunt regulator
Tol.
Voltage
Body
Vendor
TS431AILT
SOT23-5
STMicroelectronics
TS2431AILT
SOT23
NM
UM1062
Table 6.
Doc ID 018571 Rev 1
Bill of material
18/31
UM1062
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.
Doc ID 018571 Rev 1
19/31
Test results
UM1062
7
Test results
7.1
Efficiency measurement with 3.3 V output
Figure 10. Efficiency measurements at 48 V input
9RXWHIILFLHQF\#9
(IILFLHQF\>@
'&'&RQO\
RYHUDOO
,RXW>$@
!-V
Figure 11. DC-DC only efficiency measurements at different input voltages
9RXW'&'&RQO\HIILFLHQF\
(IILFLHQF\>@
'&'&9
'&'&9
'&'&9
,RXW>$@
20/31
Doc ID 018571 Rev 1
!-V
UM1062
Test results
Figure 12. Overall efficiency measurements at different input voltages
9RXWRYHUDOOHIILFLHQF\
(IILFLHQF\>@
RYHUDOO9
RYHUDOO9
RYHUDOO9
,RXW>$@
!-V
Efficiency measurement with 5 V output
Figure 13. Efficiency measurements at 48 V input
9RXWHIILFLHQF\#9
(IILFLHQF\>@
7.2
RYHUDOO
'&'&RQO\
,RXW>$@
Doc ID 018571 Rev 1
!-V
21/31
Test results
UM1062
Figure 14. DC-DC only efficiency measurements at different input voltages
9RXW'&'&RQO\HIILFLHQF\
(IILFLHQF\>@
'&'&9
'&'&9
'&'&9
,RXW>$@
!-V
Figure 15. Overall efficiency measurements
9RXWRYHUDOOHIILFLHQF\
(IILFLHQF\>@
RYHUDOO9
RYHUDOO9
RYHUDOO9
,RXW>$@
22/31
Doc ID 018571 Rev 1
!-V
UM1062
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
Doc ID 018571 Rev 1
23/31
Test results
UM1062
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
24/31
Doc ID 018571 Rev 1
UM1062
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
Doc ID 018571 Rev 1
25/31
Test results
7.3.4
UM1062
Secondary side MOSFET
Figure 21. Secondary side power MOSFET waveforms at 0 A load
Figure 22. Secondary side power MOSFET waveforms at 4 A load
26/31
Doc ID 018571 Rev 1
UM1062
7.3.5
Test results
Line transient
Figure 23 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 23. Effect of a 12 V line transient on the converter at 4 A load
Figure 24. Effect of a 12 V line transient on the converter at 0 A load
Doc ID 018571 Rev 1
27/31
Test results
7.3.6
UM1062
Load transient
Figure 25. Response of the converter to a 2 A - 4 A load transient
Figure 26. Response of the converter to a 0 A - 4 A load transient
28/31
Doc ID 018571 Rev 1
UM1062
7.3.7
Test results
Output ripple
Figure 27. 5 V output ripple measurement at 4 A
Figure 28. 5 V output ripple measurement at 4 A with infinite persistence
Doc ID 018571 Rev 1
29/31
Revision history
8
UM1062
Revision history
Table 7.
30/31
Document revision history
Date
Revision
23-Mar-2011
1
Changes
Initial release.
Doc ID 018571 Rev 1
UM1062
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