Hello,

I'm planning to use the Si3404 for a 12v/7W output (ISO-FB), and due to max height constraints I'm ending with a (really) short-list of transformers...

Actually only Wurth's 7491192912 with 7,4mm Height seems to physically fit, although I'm not sure for electrical parameters, hence my question:

Will this guy do the job ? : L:210uH / Lleak:2.5uH / RDCpri:630mOhm / RDCsec:100mOhm

P.S:Aux voltage is only 10V so I assume I won't be able to use it for V15 ? ...

Thanks for your time,

Laurent

Hello,

I would  like to use the SI3404 to achieve 5V/1A in output

I can't find the same transformer as the transformer on the SI3404 démoboard (Mentech)

I see on an other post that you you advise the FA2924-AL whereas in the datasheet it said, the output delivers 3.3V:

FA2924-AL_	40.0	36.0	0.100	0.025	0.666	1 : 0.3	2.0	3.3 V, 4.5 A
FA2805-CL_	40.0	36.0	0.108	0.040	0.621	1 : 0.4	2.0	5.0 V, 3.0 A

Is the FA2805-CL a good transformer for 5V ? 
IS the 2924-AL can be used too for 5V ?  (and Why ? )

Any help would be great.
Thank you

Hi, 

I consider using the Si34061 in a new PoE+ PD design with output voltage in the 10-12V range. 

When I look up the Si34061 on oemstrade and other sites, it looks like it is very poorly stocked. Before I can design it in I must know about long-term availability. 

Please update me on availability and lead time for the Si34061.

 

Best regards, 

Børge

I've developed a design around the si3404 outputting 24V at PoE class 3. Everything works well, power is stable and supplys the full 15W when required. The problem I'm encountering though is that the si3404 chip gets really really hot when supplying the full power load (15W), the temperature measured at the top of the chip is about 120-130C not enough to trigger thermal shutdown, but still enough to be worrying. Is this normal for this family of PoE controllers or are there things I can do to my design to improve the thermal performance?

Attached is the schematic for my design, any help would be much appreciated.

Is there any reference material for designing a Si3404 isolated flyback converter that outputs 24V as a class 3 PD? If not, can you point me in the direction of how I might calculate the requirements for one?

Can the Coilcraft FA2924-AL be used as the transformer in a 5V 15W (Class 3) Si3404 isolated flyback converter design?

The only difference I can see between the Coilcraft transformer and the recommended TOEP13-0155S1 is that the primary side inductance is 70uH in the TOEP13-0155S1 and 40uH in the FA2924-AL. Does this mean the switching frequency of the Si3404 will need to be increased to compensate for the lower inductance? Or will it suffice just as a drop in replacement? (obviously without the auxiliary coil connection).

Any help would be great.

Hello,

we would like to use the Si3402-B as a 48V to 12V isolated converter via 48V power supply only. That means we don't need PoE on the input side.

Is it possible to put the pins CT1, CT2, SP1 and SP2 simply to ground or leave them unconnected in this situation?

Backround: We already use the Si3402-B for an isolated PoE splitter in one of our projects. In new project we want to design a "PLC (Power line communication) splitter" with more or less the same dimensional and electrical requirements. Therefore we would like to reuse design from PoE splitter project regarding the isolated 48V to 12V conversion.  

Best regards

Janis Sarikas

Hi everyone,

the datasheet says that the Si3454 can work in autonomous operation without using any processor.  So let us say AUTO-Pin is set to 1.54V. End span with 15.4W.
The PD which can be connected could be a Type 1 class 0 or class 3.

1. What happens when a type 2 PD will be connected?

2. What happens when a type 1 class 1/2 PD will be connected?

For both cases, will the controller went shutdown?
For case 2: Will the controller provide the power?
Is there any signal which can be used as a trigger to reset the system?

Kind regards

Hello

I'm wanting to change the 5v EVK output voltage of the si34061(UG333 : Class 4 Isolated Evaluation Board) to 12V.

Consulting AN1130 I found section 5.10.3 that referes to the equation VOUT = 1.24V*(1 + R1/ R2).

So all I need to do is change R1 and R2?

Thanks

Hi,

though the Si3404 is on the market for a while now, documentation is still scarce. 

We are looking for a PoE solution using 802.1at Type 1 very close at maximum power, so high efficiency is a must. Therefore I have 2 questions:

• at 12 V output voltage, what efficiency gain can be expected from replacing Si3402-C with Si3404?
• What changes to Si3404-ISO-FB EVB are necessary to get 12 V output voltage?

Thanks a lot!

The transformer part numbers to change Si3402BISO eval board output voltage don't match the values given on coilcraft's homepage (refs: https://www.silabs.com/documents/public/user-guides/Si3402BISO-EVB.pdf and https://www.coilcraft.com/fa2805.cfm, https://www.coilcraft.com/fa2671.cfm)

They differ as follows:

	user guide 10W	coilcraft 10W	user guide 15W	coilcraft 15W
3.3V	EP10 FA2671	FA2671-AL_	EP13FA2924AL	FA2924-AL_
5V	EP10 FA2671	FA2672-AL_	EP13FA2924CL	FA2805-CL_
12V	EP10 FA2672	FA2732-AL_	EP13FA2805CL	FA2925-AL_

 

I assume that the values mentioned by coilcraft are correct and the table in the user guide are somehow mixed up. But I would appreciate, if someone from SiLabs support team can confirm!

Thanks!

 

Hello,

I just received my eval board for the SI34061. However, UG333 references board version 1.0, and I have received board version 1.2.
The BOMs and schematic don't match, so any modifications are extremely hard to make.
Where could I get a hold of the new UG333 with updated schematic and BOM?

Thank you very much!
ML

In my sch: 

1.   C1, C3, C4 is 1uF, 100V, X7R, but footprint is 1206, is that OK? Because 1210 is too large to place it.

2.   C2 is 10uF,  100V,  6.3mm*11mm, is that OK? Because 12uF is not common.

3.   C6 is 22uF, but footprint is 0603.

4.   C7 is 1nF, 100V, X7R, 0603 as same as C10~C17.

5.   C19, C20 is deleted.

6.   R2 is deleted,   R3,R4,R7 is 0603,    R5,R6 is 0402

7.   This is SI-52003-F
 

 

But what I used is just a common connector, so how I design? 

 

Is that OK?

or this?

My PCB just 2 layers, and space is Limited.

Hi we're developing a small product powered by PoE. Of the first three prototypes built the first worked right out of the box, the second worked for a second and then died with a puff of smoke. Thinking this was an exemplaric failure (hand build) I connected the third and that died after a second or so as well :(

The first one worked for a day, but has since then died, also releasing the "magic smoke" from the SI3402 (same symptom as the other two). I measured the 5 Volt power draw from the rest of the circuit and it is around 100mA, typically never above 200mA. When the first device worked I also noticed that the SI3402 (and the inductor, could not exactly tell) ran quite warm (I guess around 40-45°C) given the total power draw (but nothing excessively hot so it seemed).

As it is a low power device (1-2Watt) I'm solely using the internal rectifiers of the Si3402. The supply I'm testing with is a Ubiquity 48Volt/0.5Amp power injector.

It the SI3402 protected in any way? I.e. when an overcurrent is drawn will it shut down, of will it just blow (the internal rectifiers)?

 

Thanks for any help!

 

Schematics of the PoE supply (SP and CT terminals are connected directly to the RL45 jack/center taps):

 

Board layout attached (GND/Vneg plane not filled for clarity).

 

 

 

 

1. Can we use Isolated buck converter IC to regulate the DC output instead of simple buck, isolated or non isolated fly back converter topology suggested in the data sheet.

2. If yes could you help in selecting the appropriate ISO-Buck converter IC.

3. From where i can get the schematic and layout files of Si3404-ISO-FB EVB?