Silicon Laboratories UG332 User Manual

UG332: Class 3 Non-Isolated Evaluation
Board for the Si3406

The Si3406 non-isolated Flyback topology based evaluation board
is a reference design for a power supply in a Power over Ethernet
(PoE) Powered Device (PD) application.

This Si3406-non-ISO-FB EVB maximum output level is Class 3 power (

The Si3406-non-ISO-FB EVB board is shown below. The Si3406 IC integrates an IEEE

802.03at compatible PoE interface as well as a current control based dc/dc converter.
The Si3406 PD integrates two diode bridges, which can be used up to 200 mA input cur­rent, detection circuit, classification circuit, dc/dc switch, hot-swap switch, TVS overvolt­age protection, dynamic soft-start circuit, cycle-by-cycle current limit, syncrhonous gate
driver, maintain power signature (MPS), thermal shutdown and inrush current protection.

The switching frequency of the converter is tunable by an external resistor.

x 15.4 W).

η

KEY FEATURES

• IEEE 802.03at Compatible

• High Efficiency

•

High Integration

• Optional MPS Function

• Synchronous Gate Driver

• Low BOM Cost

• Transient Overvoltage Protection

• Thermal Shutdown Protection

• 5x5 mm 20-pin QFN

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UG332: Class 3 Non-Isolated Evaluation Board for the Si3406

Kit Description

1. Kit Description

The Si3406-non-isolated Flyback topology based evaluation board is a reference design for power supplies in Power over Ethernet
(PoE) Powered Device (PD) applications. The Si3406 device is described more completely in the data sheet and application notes. This
document describes the evaluation board.

The Si3406-non-ISO-FB-C3 EVB board is shown on the cover page. The schematic is shown in Figure 2.3 Si3406-Non-Isolated Fly-

back EVB Schematic: 5 V, Class 3 PD on page 4, and the layout is in 17. Board Layout. The dc output is at connectors J11(+) and

J12(–).

Boards are shipped configured to produce 5 V output voltage but can be configured for different output voltages, such as 3.3 or 12 V,
by changing resistor R14 and a few other components. Refer to “AN1130: Using the Si3406/Si34061/Si34062 PoE+ and Si3404 PoE
PD Controller in Isolated and Non-Isolated Designs” for more information. The preconfigured Class 3 signature can also be modified,
which is described as well in AN1130.

The Si3406 includes integrated diode bridge for both CT and SP connection. The integrated diode bridge can be used up to 200 mA
input current. Above 200 mA input current the external diode bridge is required.

The external diode bridge can be Schottky or silicon type.

The Si3406 device can operate with CT/SP pins open, in this configuration the external bridge should be Schottky type diode bridge.

To compensate the reverse leakage of the Schottky type diode bridges at high temperature, the recommended detection resistor should
be adjusted to the values listed in the following table:

Table 1.1. Recommended Detection Resistor Values

External Diode Bridge R

Silicon Type 24.3 kΩ

Schottky Type 24.9 kΩ

DET

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UG332: Class 3 Non-Isolated Evaluation Board for the Si3406

Getting Started: Powering Up the Si3406-non-ISO-FB EVB

2. Getting Started: Powering Up the Si3406-non-ISO-FB EVB

Ethernet data and power are applied to the board through the RJ45 connector (J1). The board itself has no Ethernet data transmission
functionality, but, as a convenience, the Ethernet transformer secondary-side data is brought out to test points.

The design can be used in Gigabit (10/100/1000) systems as well by using PoE RJ45 Magjack, such as type L8BE-1G1T-BFH from Bel
Fuse.

Power may be applied in the following ways:

• Using an IEEE 802.3-2015-compliant, PoE-capable PSE, such as Trendnet TPE-1020WS

• Using a laboratory power supply unit (PSU):

• Connecting a dc source between blue/white-blue and brown/white-brown of the Ethernet cable (either polarity), (End-span) as
shown below:

• Connecting a
as shown below:

Figure 2.1. Endspan Connection using Laboratory Power Supply

dc source between green/white-green and orange/white-orange of the Ethernet cable (either polarity), (Mid-span)

Figure 2.2. Midspan Connection using Laboratory Power Supply

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L5

330 Ohm

C6
100uF

R20
47K

J11

D19S1B

TP4 NI

D12S1B

T1

FA2924

2

9

178

10

J12

R14 9.1K

TP9

vss
NI

R21

0

R5

6.8

R15 3.24K

TP5 NI

C16 1nF

NI

R10 48.7

C32
1nF

J1

RJ-45

MX0+

1

MX0-

3

MX1+

4

PWR28PWR39PWR4

10

CT

2

LED_K2K2LED_A2A2LED_K1K1LED_A1

A1

PWR1

7

CT/MX1-

5

MX1-

6

PWR5

11

C10 1uF

Q1
FDMA8051L

TP6 NI

C17 1nF

NI

R13

0.62

C20
1nF

C9 100uF

NI

C12 1nF

NI

C4

0.01uF

+

C2
12uF

C13 1nF

NI

TP7 NI

C18 1nF

NI

R8 88.7K

C1

2.2uF

C14 1nF

NI

TP3 NI

C8

0.1uF

TP10
swo
NI

D18S1B

L4

330 Ohm

C5
1nF

+

C7 220uF

D15S1B

TP1

vpos
NI

TP8 NI

TP2
syncl

NI

U1

Si3406

FBH

1

EROUT

2

FBL

3

VDD

4

NSLEEP

5

RDET

6

HSO

7

RCL

8

RFREQ

9

SP2

10

SP111VPOS12CT213CT1

14

NT2P

15

SYNCL

16

V11

17

SWO

18

VSS

19

ISNS

20

VNEG

21

L1

330 Ohm

R2
330

R11 24.3k

C19 1nF

NI

D5

1N4148W

NI

C15 1nF

NI

D17S1B

C31

NI

C3

2.2uF

C22

0.1uF

D14S1B

L2

330 Ohm

R1
330

C11 100uF

NI

R4
27k

L3
1uH

TP12

vneg
NI

D4
RS1B

D16S1B

C21

0.22uF

D13S1B

swo

vpos vss

v11

fbl

nt2p

nt2p

vdd
Vss

vout

vss

vpos

vneg

vout

gnds

vdd

vss

vpos

erout

isns

vneg

vpos

vpos

ct2

ct1

sp2

sp1

vss

vss gnds

UG332: Class 3 Non-Isolated Evaluation Board for the Si3406

Getting Started: Powering Up the Si3406-non-ISO-FB EVB

Figure 2.3. Si3406-Non-Isolated Flyback EVB Schematic: 5 V, Class 3 PD

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UG332: Class 3 Non-Isolated Evaluation Board for the Si3406

Overall EVB Efficiency

3. Overall EVB Efficiency

The overall efficiency measurement data of the Si3406-non-ISO-FB EVB board is shown below. The input voltage is 50 V, output volt­age is 5 V.

Figure 3.1. Si3406-Non-Isolated Flyback Class 3 EVB Overall Efficiency: 50 V Input, 5 V Output, Class 3 PD

Note: The chart shows overall EVB efficiency. The voltage drop on the standard silicon diode bridge is included.

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UG332: Class 3 Non-Isolated Evaluation Board for the Si3406

SIFOS PoE Compatibility Test Results

4. SIFOS PoE Compatibility Test Results

The Si3406-non-ISO-FB EVB board has been successfully tested with PDA-300 Powered Device Analyzer from SIFOS Technologies.
The PDA-300 Powered Device Analyzer is a single-box comprehensive solution for testing IEEE 802.3at PoE Powered Devices (PDs).

Figure 4.1. Si3406-Non-Isolated Flyback C3 PD SIFOS PoE Compatibility Test Results

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-180

-90

0

90

180

-80

-60

-40

-20

0

20

40

60

80

100 1 000 10 000 100 000

UG332: Class 3 Non-Isolated Evaluation Board for the Si3406

Feedback Loop Phase and Gain Measurement Results (Bode Plots)

5. Feedback Loop Phase and Gain Measurement Results (Bode Plots)

The Si3406 device integrates a current mode controlled switching mode power supply controller circuit. Therefore, the application is a
closed-loop system. To guarantee a stable output voltage of a power supply and to reduce the influence of input supply voltage varia­tions and load changes on the output voltage, the feedback loop should be stable.

To verify the stability of the loop, the loop gain and loop phase shift has been measured.

Figure 5.1. Si3406-Non-ISOFB-EVB-C3 Measured Loop-Gain and Phase Shift

Table 5.1. Measured Loop Gain and Phase Shift

Frequency Gain Phase

Cursor 1 (Phase Margin) 19.1 kHz 0 dB 78°

Cursor 2 (Gain Margin) 47.1 kHz –7 dB 0 °

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UG332: Class 3 Non-Isolated Evaluation Board for the Si3406

Step Load Transient Measurement Results

6. Step Load Transient Measurement Results

The Si3406-non-ISO-FB EVB board's output has been tested with a step load function to verify the converters output dynamic re­sponse.

Figure 6.1. Si3406-Non-Isolated Flyback EVB PD Output Step Load Transient Test

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