TPS23754: PoE PD controller

Sijo Augustine

Prodigy 50 points

Part Number: TPS23754
Other Parts Discussed in Thread: PMP9563,

Tool/software:

While I am testing with a fresh TPS23754EVM-383 evaluation board, its working with 48V active PoE adapter(PSE).

But its not functioning with 24V passive PoE adapter(PSE).

Same 5W load in both cases.

The measured voltage between TP4&TP10 is 23.6V.

All jumpers are in default positions.

Please convey your valuable suggestions, so that I can seamlessly work with both adapters.

10 months ago

0 Diang Xing 10 months ago

TI__Mastermind 37121 points

Hi Sijo,

Thanks for reaching out!

You need to make PPD-VSS > 1.55V to enable the 24V passive PoE injector.

You need to short D2, change R4 to ~8k, configure J6 & J8 & J7 as below picture

Best regards,

Diang

0 Sijo Augustine 10 months ago in reply to Diang Xing

Prodigy 50 points

Hi Diang,

I have made the said changes and tested.

For 48V active injector its working fine.

For 24V passive injector only 9.6V is coming at the output connector J2. LEDs D12 was ON but D21 was OFF.

Initially at R4~8K, the Vppd to Vss(voltage between TP1&TP10) was 1.5V only. So I changed R4 value to 9K, then Vppd to Vss become 1.8V. But no changes on the output and indicator LEDs.

0 Diang Xing 10 months ago in reply to Sijo Augustine

TI__Mastermind 37121 points

Hi Sijo,

It may reach the max duty cycle limit ~70 - 80%. You need to change T1 if it turns ratio is PRI:SEC:AUX = 1.8:1:1. Change to 1.2:1:1

Best regards,

Diang

0 Sijo Augustine 10 months ago in reply to Diang Xing

Prodigy 50 points

Hi Diang,

Yes, my TPS23754EVM-383 board is equipped with forward transformer of Wurth-750311320, and its turns ratio is 1.8 : 1 : 1

Other compatible&available transformer given in the EVK Bom is Pulse-PA2649NL which has a turns ratio of 1.77 : 0.92 : 1

Can you suggest some forward transformer having turns ration of 1.2 : 1 : 1

0 Diang Xing 9 months ago in reply to Sijo Augustine

TI__Mastermind 37121 points

Hi Sijo,

I could not find a suitable transformer with 1.2:1:1. You could try FCT1-120D3SL which has 1:1:1 or request some costumed transformers. 1:1:1 needs ~50% duty cycle at 24V input voltage. Thanks!

Best regards,

Diang

0 Sijo Augustine 9 months ago in reply to Diang Xing

Prodigy 50 points

Hi Diang,

Thank you for the information.

I feel this coilcraft transformer availability is a challenging factor.

Can you share any PoE application circuit having 12V output from 22V to 50V inputs(passive&active)?

@ PoE/PoE+(12W/25W) power rating.

0 Diang Xing 9 months ago in reply to Sijo Augustine

TI__Mastermind 37121 points

Hi Sijo,

Sorry I did not find a qualified design. It is more common to use flyback at this power range and with a wide input voltage.

PMP9563 and TPS23754EVM-383 are both 12V output using AC forward. But they all need 36 - 57V input voltage.

Let me know if flyback is also good to you.

Best regards,

Diang

0 Sijo Augustine 9 months ago in reply to Diang Xing

Prodigy 50 points

Yes today I tested the Gate-1 period and found that its ON period is around 75% with 24V PSE and nearly 50% with 48V PSE.

But it is smoothly driving the load with this 9V.

Hope a better result with Pulse-PA2649NL, which has a turns ratio of 1.77 : 0.92 : 1

0 Sijo Augustine 9 months ago in reply to Diang Xing

Prodigy 50 points

Hi Diang,

Flyback can also use, if there is a design having 12V output.

0 Diang Xing 9 months ago in reply to Sijo Augustine

TI__Mastermind 37121 points

Hi Sijo,

Please expect delay in response when back from Thanksgiving holiday. Thanks!

Best regards,

Diang

0 Diang Xing 9 months ago in reply to Diang Xing

TI__Mastermind 37121 points

Hi Sijo,

You can check below flyback transformer can support 9 - 57V input voltage

https://www.we-online.com/components/products/datasheet/750344488.pdf

Best regards,

Diang

0 Sijo Augustine 9 months ago in reply to Diang Xing

Prodigy 50 points

Hi Diang,

Thank you for sharing the details of '750344488', a wide input voltage flyback transformer from Wurth.

Can I use this transformer with TPS23754 PoE controller chip for making a 12V output PoE PD?

I mean, by modifying the schematic of TPS23754EVM-420EVM.

If so, please share the required changes.

0 Diang Xing 9 months ago in reply to Sijo Augustine

TI__Mastermind 37121 points

Hi Sijo,

Our PoE team is currently out of office and will be back in Dec.17. Sorry for the delay.,

BR,

Diang

0 Sijo Augustine 9 months ago in reply to Diang Xing

Prodigy 50 points

Hi Diang,

I replaced the 'Wurth-750311320' transformer with 'Pulse-PA2649NL' on the TPS23754EVM-383 EVK.

But now the output voltage is switching between 1.8V and 11.8V at a frequency of 16.6 Hz(for both 24V & 48V PoE PSE).

In this EVK, the PPD pin is set above 1.55V.

0 Diang Xing 9 months ago in reply to Sijo Augustine

TI__Mastermind 37121 points

Hi Sijo,

This transformer is for flyback only. May I know if you also changed the circuit from forward converter to flyback converter? If so, could you share you updated schematic.

Sijo Augustine said:
Flyback can also use, if there is a design having 12V output.

Best regards,

Diang

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TPS23754: PoE PD controller