TPS23753A: Passiv POE

Sergey Avdjushin

Part Number: TPS23753A
Other Parts Discussed in Thread: TPS23758, TPS23750, TPS23750EVM-108

Hello!
In our products, we use POE chips from another manufacturer.
When customers connect our products to the Passive POE adapter, it often burns out.
We plan to remake the design on your chip.
Please advise the microcircuit that enabled the Passiv POE adapter. Output voltage 5 V, 10 W.TPS23753A or any other.
Sincerely, Serg.

over 4 years ago

0 Michael Pahl over 4 years ago

TI__Mastermind 21320 points

Hello Serg,

Thank you for your interest in TI PoE solutions. I would recommend our TPS23758 for your application.

We have an EVM you can test with your system to evaluate our part: http://www.ti.com/tool/TPS23758EVM-080

It is 5V /13W, synchronous rectified flyback.

Please let me know if you have any questions.

Regards,

Michael Pahl

0 Sergey Avdjushin over 4 years ago in reply to Michael Pahl

Intellectual 285 points

Thank you so much!
Did I understand correctly that this chip can work not only with a standard POE device, but also with a non-standard, cheap Passive POE adapter, which is without a POE protocol? It always carries voltage between the Ethernet wires.

I do not supply power to the Adapter connector, as shown in the diagram in the documentation, but connect the 48 Volt adapter to the Ethernet wires. Is this permissible?
Sincerely, Serg.

0 Michael Pahl over 4 years ago in reply to Sergey Avdjushin

TI__Mastermind 21320 points

Hello Serg,

The design is able to be powered if 48V was applied across VDD-VSS, even from a DC power supplies. So yes, the EVM should power up with the PoE adapter described. However, I am hesitant to say that the EVM will work with all "cheap Passive POE adapters" always. That is why I highly encourage you to order an EVM, and test it with your adapter. Then you can base your design off of the EVM or copy it completely, knowing beforehand if the passive adapter will work as a system.

Regards,

Michael Pahl

0 Sergey Avdjushin over 4 years ago in reply to Michael Pahl

Intellectual 285 points

Hello Michael!

Thank you very much for the answer.

For this chip, LDT1018-50R transformer is recommended. It has a height of 14.5 mm. It is too much for our project. Could be recommend a lower profile transformer?

Sincerely, Sergey.

0 Michael Pahl over 4 years ago in reply to Sergey Avdjushin

TI__Mastermind 21320 points

Hello Sergey,

The TPS23758 EVM uses primary side regulation (PSR). This feature eliminates the need for a optocoupler + feedback network, but requires an additional winding on the transformer for the regulation. We have tested the Linkcomm transformer and a Wurth transformer, but both are 14.5mm.

I looked at other reference designs with your voltage and power requirements, and I found a few that use Coilcraft transformers at a height of 12.7mm. They are the PMP8896.1 , PMP9175.1 , and PMP7355.1 . They all use the TPS23753A. These designs are all flybacks, but do not use PSR. This enables you to choose a flyback transformer that can meet your height requirements.

Regards,

Michael Pahl

0 Sergey Avdjushin over 4 years ago in reply to Michael Pahl

Intellectual 285 points

Hello Michael!

I looked the Design of TPS23750 Evaluation Module Flyback TPS23750EVM-108 .

It has a low profile transformer Coilcraft C1174-AL. Transformer this size is good for our project.

I'v got two ideas.

1) Can this transformer be used with the TPS23758 chip you recommended? The transformer has an additional 1-2 winding, which, perhaps, can be used in PSR mode. How do you think, is it possible? The chip that you have recommended has a low price and it's great.

2) We can use the TPS23750 chip. It has a higher price. Can you recommend this chip?

Could you advise me a cheaper transistor for this design?

Q2 - SUD15N15-95 or iRF24N15D or iRF13N15D. I see only the first transistor on sale, and it costs almost a Dollar.

Q1 - Si4840DY is Obsolete. What transistor it can be replaced? Is it possible to replace Q1 with a Schottky diode with some drop in efficiency? To reduce the price.

Sincerely, Sergey.

0 Michael Pahl over 4 years ago in reply to Sergey Avdjushin

TI__Mastermind 21320 points

Hello,

1. No the transformer cannot be used for PSR.

2. Yes I can recommend this chip.

TThe Si4840 is available on Mouser at this time: https://www.mouser.com/Semiconductors/Discrete-Semiconductors/Transistors/MOSFET/_/N-awhng?keyword=SI4840

Regards,

Michael Pahl

0 Sergey Avdjushin over 4 years ago in reply to Michael Pahl

Intellectual 285 points

Hello Michael!

I understood the solution to the problem.
We have other products with the same problems. This is a simple product and I can easily convert it to the chip that you recommended. With this design, I will check the operation of a different transformer and try to make a transformer myself.
Thank you very much for your help!

Happy New Year and wish you all the best!
With best wishes, Serg.

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TPS23753A: Passiv POE