TPS23753 circuit discussion

Hi Darwin,

I also find another source POE13F-12L.(please see attachment).

Which part is suitable for our design (12V/1A)? (POE13P-12L or (POE13F-12L)

Thank you!poe_trans.pdf

Hi Shichin,

Please see PMP8803 . This is a 12V/1A flyback solution that uses the POE13P-12L transformer. It's schematic and test report can be found in its product page below.
http://www.ti.com/tool/pmp8803

Regards,
Darwin

Hi Darwin,

Okay.

Thanks for your reply.

Regards,

Shichin

Hi Darwin,

Attachment are our schematic and board file of TPS23753.

Could you help us to review it and feed back your comment?

You can use Allegro viewer to open BRD file.

Thank you for your help!

Regards,

Shichin

TPS23753_review.zip

Hi Shichin,

Please see attached some comments regarding the schematic. Is there any particular reason to operate at 70kHz? The reference design I recommend is a complete working solution using the transformer at 250kHz (typical for PoE converter designs). I recommend sticking to this solution and same component values as the TI design to save time on debugging.

I will have some comments on the layout soon. Thanks!

TPS23753_PoE_schematic_review.pdf

Hi Darwin,

Okay. I have modified schematic as your comment.

By the way,Did you finisdh layout review?

Thanks!

Shichin

Hi Darwin,

Do you finish the layout review?

By the way,if we would like to separate giga Lan transformer with PoE from RJ45 connector,

could you please suggest Giga Lan transformer with PoE component on TPS23753?

Another component is RJ45 connector without transformer, does it ralative to PoE? or just use common component?

Thank you for your help!

 

Shichin

Hi Darwin,

Do you finish the layout review?

By the way,if we would like to separate giga Lan transformer with PoE from RJ45 LAN connector,

could you please suggest Giga Lan transformer with PoE component on TPS23753?

Another component is RJ45 connector without transformer, does it ralative to PoE? or just use common component?

Thank you for your help!

Regards,

Shichin

Hi Shichin,

Here is a list of comments regarding the layout:

• There should be no PoE_VSS plane underneath the EMI filter (FB10)
• C275 should be close to the IC
• You can add more primary ground plane underneath the transformer to help with shielding (just be sure to keep isolation spacing from the secondary
• Secondary loop could be shorter. Ground of 288 should be close to ground of D13.
• R216 and R219 should be as close to U25 as possible as pin 4 is a high impedance pin.
• There is some overlap or secondary ground with GLH ground at the RJ45 connector. There should be some spacing here.

For the most part, the layout looks good!

If looking for a separate data transformer that is 1G capable, please see below link to Wurth transformer we use on some of our TI designs. Thanks!

Hi Darwin,

Okay, Thank you for your help!

 

Sincerely,

Shichin

Hi Darwin,

Sorry, I modified the size of PCB and need your help to review layout file again.(Please see attachment)

Thank you for your help!

Sincerely,

ShichinTPS23753_review_1126.zip

Hi Schichin,

From the new layout, it looks like there were only a few minor changes that were made from what we recommended last time. For the most part, the layout looks okay.

Hi Darwin,

Thanks for your replied.

Is it okay that we add PoE_RTN poly in relative area of all PCB layers?

 

Thanks!

Shichin

Hi Shichin,

Yes, as long as PoE_RTN poly stays on the converter side components (not past the EMI filter or secondary components in all layers), it is okay to put on all PCB layers.

Hi Darwin,
Okay thanks for your review!
By the way, I would like to know how to set PD class in our system.
In TPS23753 datasheet (Table 2. Class Resistor Selection), it seems that class0 power range (0.44 watt~12.95 watt) include class3 (6.49 watt~12.95 watt), so set class0 is okay to support class3? If it is, why need separate to class3?
Thanks for your support!

Sincerely,
Shichin

Hi Shichin,

Class 0 or Class 3 can be used for 13W solutions. Class 1-3 was designed for more granularity in max power consumption for the PSE. A PSE will default to Class 0 if the PD does not support classification.

Classifying a PD to its power consumption helps the PSE system in optimizing and managing its power distribution.

Regards,
Darwin

Hi Darwin,

Thanks for your answer!

We have a PoE product which design TPS23753 inside and customer feedback that  PD cannot power on from PSE of PoE+.

But it can power on normally from PSE of PoE. I would like to know if any different design of TPS23753 when it get power from PSE of 

PoE and PoE+?  or power class setting will impact it's power on ?

Thank you for your help!

Sincerely,

Shichin

Hi Schichin,

A Type 2 PSE (PoE+) should turn on a Type 1 PD. Do you have waveforms of the VDD-VSS? and Input current? Also a schematic of their design will be helpful.

Thanks!

Hi Darwin,

Thanks for your support!

Attachment is the schematic.

Thanks for your help!

Sincerely,

Shichin

TPS23753_Pre-project.pdf

Hi Darwin,

I would like to know the placement of a diode on output.

Please see attachment, there are two kinds of placement of diode on output side.

First picture is D10 and second picture is D4.

What is the purpose of the diode? Why use two kinds of placement (thru T2 and without thru T2)?

Thanks!

Sincerely,

JeferDiode placement.docx

Hi Shichin,

Since Darwin has a buesniss trip this week, I would replace him to answer your question.

The function of this diode is to block the energy deliver to secondary side when primary MOSFET is on.(energy store in primary magnetizing inductance)

Base on the dot on the transformer, so we have the different placement of the diode. 

-Ben

  Please click the Verify Answer button on this post if it answers your question. Thanks!

Hi Ben,

Thanks for your support!

Please see attachment, so based on the same transformer, the placement option 1 and option 2 are the same?

Thanks!

JeferPlacement option.docx