SILABS DO1608C-102ML Isolated evaluation board for the si3402b Datasheet

Si3402BISO-EVB
I SOLA TED E VALUATION B OAR D FOR TH E Si3402B
1. Description
The Si3402B isolated evaluation board (Si3402BISO-EVB Rev 2) is a reference design for power supplies in
Power over Ethernet (PoE) Powered Device (PD) applications. The Si3402B is described more completely in the
data sheet and application notes. This document describes only the Si3402BISO-EVB evaluation board. An
evaluation board demonstrating the non-isolated application is described in the Si3402B-EVB User’s Guide.
2. Planning for Successful Designs
Silicon Labs strongly recommends the use of the schematic and layout databases provided with the evaluation
boards as the starting point for your design. Use of external components other than those described and
recommended in this document is generally discouraged. Refer to Table 2 on page 9 for more information on
critical component specifications. Careful attention to the recommended layout guidelines is required to enable
robust designs and full specification compliance. To help ensure design success, please submit your schematic
and layout databases to www.silabs.com/support for review and feedback.
3. Si3402B Board Interface
Ethernet data and power are applied to the board through the RJ-45 connector (J1). The board itself has no
Ethernet data transmission functionality, but, as a convenience, the Ethernet transformer secondary is brought out
to the test points. Power may be applied in the following ways:

Connecting a dc source to Pins 1, 2 and 3, 6 of the Ethernet cable (either polarity).
Connecting a dc source to Pins 4, 5 and 7, 8 of the Ethernet cable (either polarity).
 Using an IEEE 802.3-2015-compliant, PoE-capable PSE, such as Trendnet TPE-1020WS.

The Si3402BISO-EVB board schematics and layout are shown in Figures 1 through 6.
The dc output is at connectors J11(+) and J12(–). Boards are generally shipped configured to produce +5 V output
voltage but can be configured for +3.3 V or other output voltages as shown in Table 2 on page 9. The
preconfigured Class 3 signature also can be modified according to Table 3 on page 10. The D8–D15 Schottky-type
diode bridge bypass is recommended only for higher power levels (Class 3 operation). For lower power levels,
such as Class 1 and Class 2, the diodes can be removed. When the Si3402B is used in external diode bridge
configuration, it requires at least one pair of the CTx and SPx pins to be connected to the PoE voltage input
terminals (to the input of the external bridge).
The feedback loop compensation has been optimized for 3.3, 5, 9, and 12 V output as well as with standard and
low ESR capacitors in the output filter section (Table 2 on page 9). The use of low ESR capacitors is recommended
for lower output ripple, improved load transient response and low temperature (below 0 °C) operation.
Rev. 1.2 4/16
Copyright © 2016 by Silicon Laboratories
Si3402BISO-EVB
K2
11
anode
LED_K2
PWR5
A2
LED_A2
K1
MX0+
CT
MX0TDP
TDN
4
5
6
7
RDP
CT
RDN
1
2
3
RJ-45
J1
L4 330 Ohm
L3 330 Ohm
At least one pair of CT1/CT2 or
SP1/SP2 should be connected.
TP6 NI
TP7 NI
TP3 NI
TP4 NI
TP5 NI
R2
49.9K
Vposs
NI
12uF
1uF
11
12
13
0
Vss
1uF
C3
Si3402B
1uF
C4
NC
Vdd
NC
EROUT
4
3
2
1
1nF
2
1
NI
Vss
TP2
swo
FA2924
T1
10:3 secondary
C19
Figure 1. Si3402B Schematic—5 V, Class 3 PD
Vneg is a thermal plane as well as ESD and EMI.
Use thermal vias to at least 1 inch square plane
on backside 1 to 1.2mm pitch 0.3 to 0.33mm diameter.
C18
0.1uF
SP1
Vpos
CT2
CT1
U1
+ C2
C1
14
Capacitors C10-C17 are for ESD immunity..
Place optional bypass diodes for high power applications (>7W) in parallel.
L2 330 Ohm
GNDI
L5 330 Ohm
PWR1
MX1+
CT/MX1MX1-
PWR3
9
PWR4
10
LED_K1
A1
LED_A1
PWR2
8
15
cathode
D15
SS2150
1nF
C10
D14
SS2150
1nF
C11
D13
SS2150
1nF
C12
1nF
C13
16
NC
9
Vssa
SP2
10
D12
SS2150
Connect transformer and
input filter caps together
minimizing area of return
loop and then connect
to Vpos plane.
8
R3
Vneg
18
SWO
17
NC
RCL
D1
D2
TP1
R4
HSO
7
48.7
19
VSS2
20
5
24.3k
RDET
6
FB
nploss
1N4148W
DFLT30A-7
Vpos is an EMI and ESD plane. Use top layer.
R12 0
J1:A1, K1 must be isolated from A2,K2
1nF
C14
D11
SS2150
1nF
C15
D10
SS2150
D9
SS2150
1nF
C16
D8
SS2150
1nF
C17
0.1uF
C22
Rev. 1.2
15nF
2
10
9
7
8
C20
C21
R1
330
3.3nF
C9
GNDI
0
R8
+
J12
C5
1000uF
5V
BND_POST
R5
36.5K
R6
12.1K
BND_POST
VO618A-3X017T
U2
C6
100uF
1uH
L1
J11
400 W Cesar Chavez St, Austin, TX
78701, United States
1nF
U3
TLV431
R11
4.99K
R7
2.05K
10
470pF
GNDI
R10
C7
PDS1040
D3
Vout pos plane for EMI
Si3402BISO-EVB
Figure 2. Si3402B Layout (Top Layer)
Si3402BISO-EVB
Rev. 1.2
3
Figure 3. Primary Side (Layer 2)
Si3402BISO-EVB
4
Rev. 1.2
Figure 4. Internal 1 (Layer 3)
Si3402BISO-EVB
Rev. 1.2
5
Figure 5. Internal 2 (Layer 4)
Si3402BISO-EVB
6
Rev. 1.2
Figure 6. Secondary Side (Bottom Layer)
Si3402BISO-EVB
Rev. 1.2
7
Si3402BISO-EVB
4. Bill of Materials
The following bill of materials is for a 5 V Class 3 design. For Class 1 and Class 2 designs, in addition to updating
the classification resistor (R3), the external diode bridge (D8–D15) can be removed to reduce BOM costs. Tables 2
and 3 list changes to the bill of materials for other output voltages and classification levels. Refer to “AN956: Using
the Si3402B PoE PD Controller in Isolated and Non-Isolated Designs” for more information.
Table 1. Si3402BISO-EVB Bill of Materials
Qty
Value
Ref
Voltage
Tol
Type
PCB Footprint
Mfr Part Number
Mfr
3
1 µF
C1, C3, C4
Rating
100 V
±10%
X7R
C1210
C1210X7R101-105K
Venkel
1
12 µF
C2
100 V
±20%
Alum_Elec
C2.5X6.3MM-RAD
EEUFC2A120
Panasonic
1
1000 µF
C5
6.3 V
±20%
Alum_Elec
C3.5X8MM-RAD
ECA0JM102
Panasonic
1
100 µF
C6
6.3 V
±10%
X5R
C1210
C1210X5R6R3-107K
Venkel
1
470 pF
C7
50 V
±10%
X7R
C0805
C0805X7R500-471K
Venkel
1
3.3 nF
C9
16 V
±10%
X7R
C0805
C0805X7R160-332K
Venkel
8
1 nF
C10, C11, C12, C13,
C14, C15, C16, C17
100 V
±10%
X7R
C0603
C0603X7R101-102K
Venkel
1
0.1 µF
C18
100 V
±10%
X7R
C0805
C0805X7R101-104K
Venkel
2
1 nF
C19, C20
3000 V
±10%
X7R
C1808
C1808X7R302-102K
Venkel
1
15 nF
C21
16 V
±10%
X7R
C0805
C0805X7R160-153K
Venkel
1
0.1 µF
C22
16 V
±10%
X7R
C0805
C0805X7R160-104K
Venkel
1
1N4148W
D1
2A
100 V
Fast
SOD123
1N4148W
Diodes Inc
1
DFLT30A-7
D2
4.65 A
30 V
Zener
POWERDI-123
DFLT30A-7
Diodes Inc.
1
PDS1040
D3
10 A
40 V
Schottky
POWERDI-5
PDS1040-13
Diodes Inc.
8
SS2150
D8, D9, D10, D11,
D12, D13, D14, D15
2A
150 V
Single
DO-214AC
SS2150-LTP
MCC
1
RJ-45
J1
Receptacle
RJ45-SI-52004
SI-52003-F
Bel
2
BND_POST
J11, J12
15 A
Banana
Banana-Jack
101
ABBATRON
HH SMITH
1
1 µH
L1
2.9 A
±20%
Shielded
IND-6.6X4.45MM
DO1608C-102ML_
Coilcraft
4
330 
L2, L3, L4, L5
1500 mA
SMT
L0805
BLM21PG331SN1
MuRata
1
330 
R1
1/10 W
±1%
ThickFilm
R0805
CR0805-10W-3300F
Venkel
1
49.9 k
R2
1/10 W
±1%
ThickFilm
R0805
CR0805-10W-4992F
Venkel
1
48.7 
R3
1/8 W
±1%
ThickFilm
R0805
CRCW080548R7FKTA
Vishay
1
24.3 k
R4
1/8 W
±1%
ThickFilm
R0805
CRCW080524K3FKEA
Vishay
1
36.5 k
R5
1/10 W
±1%
ThickFilm
R0805
CR0805-10W-3652F
Venkel
1
12.1 k
R6
1/10 W
±1%
ThickFilm
R0805
CR0805-10W-1212F
Venkel
1
2.05 k
R7
1/16 W
±1%
ThickFilm
R0603
CR0603-16W-2051F
Venkel
2
0
R8, R12
2A
ThickFilm
R0805
CR0805-10W-000
Venkel
1
10 
R10
1/10 W
±1%
ThickFilm
R0805
CR0805-10W-10R0F
Venkel
1
4.99 k
R11
1/10 W
±1%
ThickFilm
R0805
CR0805-10W-4991F
Venkel
1
FA2924
T1
XFMR-FA2924
FA2924-AL
Coilcraft
1
Si3402B
U1
1
VO618A-3X017T
U2
1
TLV431
U3
TP1, TP2, TP3, TP4,
TP5, TP6, TP7
100
PD
QFN20N5X5P0.8
Si3402B
Silicon Labs
SO4N10.16P2.54-AKEC
VO618A-3X017T
Vishay
Shunt
TLV431-DBZ
TLV431BCDBZR
TI
Loop
Testpoint
5001
Keystone
Not Installed Components
7
8
Black
Rev. 1.2
Si3402BISO-EVB
Table 2. Component Selection for other Output Voltages and Filter Types
3.3 V Output
Transformer*
EP10 FA2671
EP13FA2924AL
Output Rectifier:
PDS1040
Reference
Any TLV431
Snubber: R10, C7
10 W, 470 pF
R5
R6
C6
C5
Panasonic
R7,
R8, R12
C9,C21
Standard ESR Output
Filter
24.3 k
14.7 k
100 µF
X5R
1000 µF
6.3 V
ECA0JM102
500 , 1.1 k,
475 
10 nF, 33 nF,
Low ESR Output Filter
24.3 k
14.7 k
100 µF
X5R
560 µF
6.3 V
5.0 V Output
Transformer*
EP10 FA2671
EP13FA2924CL
EEUFM0J561 324 , 2 k, 820 
Output Rectifier
PDS1040
Snubber: R10, C7
10Ω, 470 pF
10 nF, 100 nF
Reference
Any TLV431
R5
R6
C6
C5
Panasonic
R7,
R8, R12
C9, C21
Standard ESR Output
Filter
36.5 k
12.1 k
100 µF
X5R
1000 µF
6.3 V
ECA0JM102
2.05 k,
0 , 0 
3.3nF, 15 nF
Low ESR Output Filter
36.5 k
12.1 k
100 µF
X5R
560 µF
6.3 V
EEUFM0J561
2.05 k,
0 , 0 
3.3nF, 33 nF
9.0 V Output
Transformer*
EP10 FA2672
EP13FA2805CL
Output Rectifier:
PDS5100
Snubber: R10, C7
20 , 68 pF
R5
R6
C5
Panasonic
R1,R7,
R8, R12
C9,C21
C6
Reference
Higher voltage e.g.,
TLV431ASNT1G
Standard ESR Output
Filter
66.5 k 22 µF X5R
10.5 k
16 V
470 µF
16 V
ECA1M471
1.3 k3 k,
0 , 0 
10 nF, 15 nF
Low ESR Output Filter
66.5 k 22 µF X5R
10.5 k
16 V
330 µF
16 V
EEUFM1C331
3 k,
0 , 0 
10 nF, 15 nF
12.0 V Output
Transformer* EP10 Output rectifier: PDS5100
FA2672
Snubber: R10, C7
EP13FA2805CL
20 , 68 pF
R5
R6
C6
Reference
Higher Voltage e.g.,
TLV431ASNT1G
C5
Panasonic
R1,R7,
R8, R12
C9,C21
Standard ESR Output
Filter
88.7 k 22 µF X5R
10.2 k
16 V
470 µF
16 V
ECA1M471
1.3 k3 k,
0 , 0 
10 nF, 15 nF
Low ESR Output Filter
88.7 k 22 µF X5R
10.2 k
16 V
330 µF
16 V
EEUFM1C331
1.3 k3 k,
0 , 0 
10 nF, 15 nF
*Note: Coilcraft part number. EP13 core is recommended for >10 W output power.
Rev. 1.2
9
Si3402BISO-EVB
Table 3. Component Selection for Different Classification Levels
10
Class
R3 (1%)
0
Open
1
140
2
75
3
45.3
Rev. 1.2
Si3402BISO-EVB
A PPENDIX —Si3402BISO D E S I G N A N D L A Y OUT
C H EC K LI S T
Introduction
Although all four EVB designs are preconfigured as Class 3 PDs with 5 V outputs, the schematics and layouts can
easily be adapted to meet a wide variety of common output voltages and power levels.
The complete EVB design databases for the standard 5 V/Class 3 configuration are included in the EVB kit and
can also be requested through Silicon Labs customer support at www.silabs.com/PoE under the “Documentation”
link. Silicon Labs strongly recommends using these EVB schematics and layout files as a starting point to ensure
robust performance and to help avoid common mistakes in the schematic capture and PCB layout processes.
Following are recommended design checklists that can assist in trouble-free development of robust PD designs:
Refer also to the Si3402B data sheet and AN956 when using the checklists below.
1. Design Planning Checklist:
a. Silicon Labs strongly recommends using the EVB schematics and layout files as a starting point as you
begin integrating the Si3402B into your system design process.
b. Determine your load’s power requirements (i.e., VOUT and IOUT consumed by the PD, including the
typical expected transient surge conditions). In general, to achieve the highest overall efficiency
performance of the Si3402, choose the highest voltage used in your PD and then post regulate to the
lower supply rails, if necessary.
c. If your PD design consumes >7 W, make sure you bypass the Si3402’s on-chip diode bridges with
external Schottky diode bridges or discrete Schottky diodes. Bypassing the Si3402’s on-chip diode
bridges with external bridges or discrete diodes is required to help spread the heat generated in designs
dissipating >7 W.
d. Based on your required PD power level, select the appropriate class resistor value by referring to Table 3
of AN956. This sets the Rclass resistor (R3 in Figure 1 on page 2).
e. The feedback loop stability has been checked over the entire load range for the specific component
choices in Table 1. Low ESR filter capacitors will give better load transient response and lower output
ripple so they are generally preferred. For the standard ESR capacitor, the ESR increase at very low
temperatures may cause a loop stability issue. A typical evaluation board has been shown to exhibit
instability under very heavy loads at –20 °C. Due to self-heating, this condition is not a great concern.
However, using a low ESR filter capacitor solves this problem (but requires some recompensation of the
feedback loop). Silicon Laboratories recommends against component substitution in the filtering and
feedback path as this may result in unstable operation. Also, use care in situations that have additional
capacitive loading as this will also affect loop stability.
2. General Design Checklist Items:
a. ESD caps (C10–C17 in Figure 1) are strongly recommended for designs where system-level ESD
(IEC6100-4-2) must provide >15 kV tolerance.
b. If your design uses an AUX supply, make sure to include a 3  surge limiting resistor in series with the
AUX supply for hot insertion. Refer to AN956 when AUX supply is 48 V.
c. Silicon Labs strongly recommends the inclusion of a minimum load (250 mW) to avoid switcher pulsing
when no load is present, and to avoid false disconnection when less than 10 mA is drawn from the PSE.
If your load is not at least 250 mW, add a resistor load to dissipate at least 250 mW.
d. If using PLOSS function, make sure it’s properly terminated for connection in your PD subsystem. If
PLOSS is not needed, leave this pin floating.
Rev. 1.2
11
Si3402BISO-EVB
3. Layout Guidelines:
a. Make sure the VNEG pin of the Si3402B is connected to the backside of the QFN package with an
adequate thermal plane, as noted in the data sheet and AN956.
b. Keep the trace length from connecting to SWO and retuning to Vss1 and Vss2 as short as possible.
Make all of the power (high current) traces as short, direct, and thick as possible. It is a good practice on
a standard PCB board to make the traces an absolute minimum of 15 mils (0.381 mm) per Ampere.
c. Usually one standard via handles 200 mA of current. If the trace will need to conduct a significant
amount of current from one plane to the other use multiple vias.
d. Keep the circular area of the loop from the Switcher FET output to the inductor or transformer and
returning from the input filter capacitors (C1–C4) to Vss2 as small a diameter as possible. Also, minimize
the circular area of the loop from the output of the inductor or transformer to the Schottky diode and
returning through the fist stage output filter capacitor back to the inductor or transformer as small as
possible. If possible, keep the direction of current flow in these two loops the same.
e. Connect the sense points to the output terminals directly to avoid load regulation issues related to IR
drops in the PCB traces. The sense points are the output side of R5 and Pin 3 of TLV431.
f.
Keep the feedback and loop stability components as far from the transformer/inductor and noisy power
traces as possible.
g. If the outputs have a ground plane or positive output plane, do not connect the high current carrying
components and the filter capacitors through the plane. Connect them together and then connect to the
plane at a single point.
h. As a convenience in layout, please note that the IC is symmetrical with respect to CT1, CT2, SP1 and
SP2. These leads can be interchanged. At least one pair of CT1/CT2 or SP1/SP2 should be connected.
To help ensure first pass success, please submit your schematics and layout files to www.silabs.com/support for
review. Other technical questions may be submitted as well.
12
Rev. 1.2
Si3402BISO-EVB
DOCUMENT CHANGE LIST
Revision 1.1 to Revision 1.2

Initial release of Si3402BISO-EVB User’s Guide,
modified from Si3402-ISO-EVB User’s Guide
Revision 1.1.
Rev. 1.2
13
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