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How would you power 4x separate isolated RS485 transceivers?

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jneudorf:
I am considering using 4x Recom RFMM-0505S DC-DC modules ($1.31 each at Mouser) for power, and Analog's ADUM1201ARZ-RL7 ($0.65 at LCSC) to get the signal across.

I'd rather just make some isolated converter like in http://www.ti.com/lit/ug/tidu590/tidu590.pdf but the Wurth 760390014 only has a single output and costs $1.25 on its own.

Should I consider using Coiltronics Versa-Pac or Coil-Craft Hex-Path HPH1 series, or are there other options that might work? I can't find Asian sources that seem similar to these.

The context is bi-directional DMX/RDM at 250kbps.

David Hess:
I would use a pair of trifillar wound transformers in an inverter circuit.  This only requires one simple driver.

T3sl4co1l:
Hex-Path is a good option, mind the isolation is only a hundred volts or whatever -- fine for signal purposes, but beware of ESD damaging it.  (You could bridge grounds with a little MOV or TVS to control this.)

If I needed more, or lower cost, I might consider planar transformers -- do it all in the PCB itself.  This is a more advanced option though, as you're doing the transformer design yourself, and you don't have many protos to iterate on.



--- Quote from: David Hess on December 19, 2019, 01:10:56 am ---I would use a pair of trifillar wound transformers in an inverter circuit.  This only requires one simple driver.

--- End quote ---

An interesting option would be to abuse some CMCs (data or data/power type), driven with a few logic gates or a gate driver, to make a simple chopper; FWB the secondaries and there you go.  Put a bunch of primaries in parallel -- one for each channel -- not really a need for multifilar, the dual-line kind (which are usually bifilar) should be good enough.  Downside is the lack of current limiting, which may have workarounds (e.g., use a motor-driver H-bridge chip, and use its internal current limiting, or supply it with a current limiter), and of course the cross-regulation is limited by leakage inductance.

Tim

rvalente:
This topic is very similar to yours,
 https://www.eevblog.com/forum/projects/isolated-5v-5-10ma-supply/msg2816550/#msg2816550

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