THVD8000: coupled inductors

Uriel Tallon

Part Number: THVD8000
Other Parts Discussed in Thread: THS6222

Hi folks,

I would have liked to know if it was possible to use coupled inductors for AC coupling with the THVD8000 in order to reduce the number of components on the board (in the case of a Power Over Data Line application with RS-485)? If yes, is there some special considerations to take into account?

Thank you in advance!

over 3 years ago

0 Clemens Ladisch over 3 years ago

Guru 316760 points

These questions talk about using a pulse transformer:

Using THVD8000 with transformer coupling instead of capacitor coupling
Question about connection of THVD8000
Questions for THVD8000 application

Look at Power-over-Ethernet applications.

+1 Parker Dodson over 3 years ago

TI__Guru 52172 points

Hi Uriel,

So the short answer is the standard implementation of the THVD8000 PowerBus requires capacitive coupling for data signal coupling. Using coupled inductors to couple the modulated data to the power line isn't supported.

The long answer is that - you can drive a transformer with the THVD8000 + Line Driver (we have tested with the THS6222).This application note, linked here: https://www.ti.com.cn/cn/lit/an/slla590/slla590.pdf?ts=1663253839566&ref_url=https%253A%252F%252Fwww.google.com%252F, explains an application of interfacing the THVD8000 with High Voltage and/or low impedance applications. The protection circuit may not need to be as robust as suggested in the application note if the application is working at <= 30V; but the overall architecture would be similar. The issue is - I don't know if this will actually reduce BOM components - while it does remove the need for inductors to couple power onto the shared bus - it adds another IC + its passives and potentially additional protection elements. So I don't know if it will be beneficial to move this way if BOM reduction is what you are trying to do - however if you are looking for isolation this application note can help.

I agree with Clemens looking into possible power over Ethernet applications may be a beneficial direction for you to take if the RS-485 options are not meeting your needs.

Please let me know if you have any questions and I will see what I can do!

Best,

Parker Dodson

0 Uriel Tallon over 3 years ago in reply to Parker Dodson

Prodigy 10 points

Hi Parker,

Thank you very much for your clarification. Indeed, the transformer-based solution may not be the best way to reduce the BOM.

We have already dabbled into PoE and right now we wanted to make a proof of concept about Power over Data Line with RS-485. I think we will still going for it, starting with a prototype that we will optimize on the fly.

Cheers,

Uriel

0 Parker Dodson over 3 years ago in reply to Uriel Tallon

TI__Guru 52172 points

Hi Uriel,

Alright sounds good. If you have any more questions please don't hesitate to reach out!

Best,

Parker Dodson

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THVD8000: coupled inductors