TPS23756 implement discussion

Hi,

Thank you for your replied!

According to our product design specification, output power will set 13volt@2A, Should I use Flyback or Forward topology ?

What components need to be changed on EVM?(see attachment)slvu329a_TPS23756.pdf

Thank you!

Hi Darwin,

Thank you for your answer.

Please see attachment for adapter Rring option3 circuit, is the circuit okay to implement ?

Thanks!TPS23756_PoE_Adapter ORing_option3_PoE priority.docx

TPS23756_TPS23754_discussion.docxHi Darwin,

Thanks for your answer.

I have some issues below,

1.  about Oring option3,please see green mark in the Item1 of attachment.

     What does it mean of "When used with a secondary-side synchronous rectifier, this circuit needs special attention to
     turn the rectifier off when the adapter takes over. This prevents power from flowing backwards and
     powering the primary side of the converter." ?

2. About the U2 Optocoupler (see item2 of attachment), can I replace FOD817AS with TCMT1107?

   I found many versions of TPS23756 EVM using TCMT1107 rather than FOD817AS.

    If I using TCMT1107, should I change R21,R22 (see item2 of attachment)?

    How to calculate R21 and R22?

Thanks!

Hi Jefer,
Since you have the diodes ORing in your previous schematic, you do not have to worry about back biasing the primary. What the app note is referring to is if you try to drive the output with power while the converter has no power at the input, it is possible the controller might have some voltage and try to switch. This is not IC specific but for particular power supply topologies.

As for the optos, yes you can use TCMT part as they are similar. I don't expect that a change the external biasing components will be needed.

Hi Darwin,

Okay, thank you for your answer.

I have another issue about using TPS23754 and TPS23756.

I would like to know , If the only one difference between TPS23754 and TPS23756 is support  voltage of adapter ?

The minimum support adapter voltage of TPS23754 is 24volt while TPS23756 is 12 volt, does it mean if your adapter is 12volt

and you want implement Oring option1 and option2 then you must use TPS23756 , but if you will implement Oring option3 than

you can use TPS23954 or TPS23756?

Thanks!

Hi Darwin,

Okay, thank you for your reply.

By the way, do you have any suggest part of PoE+ transformer support 10/100/1000 LAN?

Thanks!

Hi Darwin,

About the PoE LAN connector, if I use seprate solution (One RJ45 connector and one PoE+ transformer),

Can I use standard RJ45 8pin connector or need find  RJ45 connector that support PoE+?

Thanks!

Hi Darwin,

Okay.

Thanks!

Hi Darwin,

If I want to design TPS23753 (802.3af,PD,12.95W) with giga LAN, can I use the same source part of RJ45 with transformer which design in TPS23756(802.3at,PD,25W)?

Does diode bridge also use the same source (B1100) in TPS23753 and TPS23756?

Please also see attachment for more detail.

Thanks!Components check.docx

Hi Shichin,

Yes, you can use the same PoE front end design (Magjack and diode bridge) on the TPS23753A design front end as the TPS23756 design front end.

Hi Darwin,

Oaky,thank you for your reply.

By the way, does TI have EVM of TPS23753 which using Giga Lan application?

Hi Shichin,

Please see TPS23753AEVM-235. This uses the 7499511611A magjack than can support 1000baseT.

Regards,

Darwin