TPS23734: TPS23734 PoE PD

Sijo Augustine

Prodigy 50 points

Part Number: TPS23734
Other Parts Discussed in Thread: TPS23730, TPS23754, TPS23756, LM5071, TPS23754EVM-383

Tool/software:

Can I connect TPS23734 PoE PD to a 24V/48V passive PoE PSE?

Hope adapter ORing feature can be used in this case?

10 months ago

+1 Diang Xing 10 months ago

TI__Mastermind 37121 points

Hi Sijo,

Thanks for reaching out!

TPS23734 can work well with 48V passive PoE PSE, and in this case, the adapter priority using APD pin is also good. But for 24V passive PoE PSE the PD's internal hotswap cannot be turned on since 24V is below the 35.8 - 39.5 V UVLO at VDD-VSS.

TPS23730 can work for both 24V/48V passive PoE PSE, since it has a PPD pin can be used to turn on the PD internal hotswap at a lower VDD-VSS voltage. And adapter priority using APD pin is also good with TPS23730.

Attachment is a 2TPS23730 based design can be used with 24V passive PSE. And you can refer TPS23730EVM (https://www.ti.com/tool/TPS23730EVM-093) for the adapter oring circuit using APD pin.

PMP22628C(001)_Sch.PDF

Best regards,

Diang

0 Sijo Augustine 10 months ago in reply to Diang Xing

Prodigy 50 points

Hi,

Thank you for the valuable information. Now I am able to choose TPS23730 in my design.

0 Sijo Augustine 10 months ago in reply to Diang Xing

Prodigy 50 points

Can you give some part numbers of some other PoE PD ICs that supports IEEE803.at standard and also 48V/24V passive PoE PSEs.

0 Diang Xing 10 months ago in reply to Sijo Augustine

TI__Mastermind 37121 points

Hi Sijo,

In AT 25.5W PDs, TPS23754 and TPS23756 also have the PPD pin can be used for 48V/24V passive PoE PSEs.

TPS23754 is more recommended for passive PoE with 18 - 57 V input. TPS23756 is more recommended for passive PoE with 15 - 57 V input. TPS23754 is more recommended for 24/48V since it has 15V higher VCC voltage for easier start up time control.

Best regards,

Diang

0 Sijo Augustine 10 months ago in reply to Diang Xing

Prodigy 50 points

Hi Diang,

Thank you for the information.

I am in a phase of cost Vs performance analysis before starting the design.

Can you recommend a PoE PD IEE803.af controller chip also, that can support both 24V and 48V passive PSE.

0 Diang Xing 10 months ago in reply to Sijo Augustine

TI__Mastermind 37121 points

Hi Sijo,

LM5071 can do it which has a programable UVLO and can configure a primary side adapter before PD.

Since at standard cover af standard, you can also use TPS23754 and TPS23756 in af power level applications.

Best regards,

Diang

0 Sijo Augustine 10 months ago in reply to Diang Xing

Prodigy 50 points

Hi Diang,

Thank you for the information.

I understand that in LM5071/TPS23754/TPS23730 based PoE PD design, the PoE circuit will be functional, and its output voltage will be stable even though we changed PSE from 48V_active to 48V_ passive and to 24V_passive?

Adapter ORing feature is found on the datasheet. Hope I need not do any manual jumper selection, while changing the LAN connection from a 48V_active switch/PSE to 24V_passive switch/PSE?

0 Raymond Lin 10 months ago in reply to Sijo Augustine

TI__Mastermind 34676 points

Hi Sijo,

PoE team is currently out of office and will be back in Nov.12. Sorry for the delay.

Thanks and Regards,

Raymond Lin

+1 Diang Xing 10 months ago in reply to Raymond Lin

TI__Mastermind 37121 points

Hi Sijo,

Your DC/DC circuit design decides if the output voltage can be stable or not when you make input voltage changes.

When input voltage changes, a bulk cap (normally > 33uF for Class-4) can help to slow down the transient, and LM5071/TPS23754/TPS23730 can have max duty cycle ~70 - 80% and it is normally not hard for smooth transient when flyback transformer has a suitable turns ratio and inductance. And it is better to have a phase margin 45 - 60 degree and gain margin > 10dB.

I attached PMP22628 is a 16 - 57V input PoE using TPS23730. It can work with 24V in or 48V in without manual configuration changes. Hope it can help.

PMP22628C(001)_TI-BOM.xls 5327.PMP22628C(001)_Sch.PDF

Best regards,

Diang

0 Sijo Augustine 10 months ago in reply to Diang Xing

Prodigy 50 points

Hi Diang,

My design is based on TPS23754. I am testing both passive and active PoE functionality on TPS23754EVM-383 evaluation board. Its feedback shared in a new post. Thank you.

0 Diang Xing 10 months ago in reply to Sijo Augustine

TI__Mastermind 37121 points

Hi Sijo,

I saw your new post. I will close this thread for now. Thanks.

Best regards,

Diang

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TPS23734: TPS23734 PoE PD