low cost isolation amplifier

They had to pay the burglars to snatch some out of the Smithsonian so they could put them back on the shelf

But I really need a low cost isolation amplifier.

Looks like roughly $3 each. SiLabs has a three channel isolated ADC that is interesting, if I can figure out the actual throughput rate. Si8902.

On a sunny day (Wed, 17 Nov 2021 20:19:54 -0800) it happened snipped-for-privacy@highlandsniptechnology.com wrote in snipped-for-privacy@4ax.com:

Nice to have it all in that chip, but the modulation - demodulation is always a bit .. Not Needed? I remember back in the seventies using optocouplers for audio and a bit higher frequencies, there was a chip for that too, no idea what the type number was. May still have one somewhere,

TI used to make the (iirc) TIL311, which had a LED and two photodiodes, all mutually isolated. You used one PD to servo the LED brightness, and used the other one as the output.

Cheers

Phil Hobbs

Am 18.11.21 um 05:19 schrieb snipped-for-privacy@highlandsniptechnology.com:

I had one of these, internally capacitively coupled, underpopulated DIL-28 with just 8 pins or so, 20 years ago. It had to be statically shielded, or a 400V AC line 10 cm above it would drive it nuts. ISO-12? could fit.

cheers, Gerhard

I haven't used SiLabs isolated ADCs but I have used their isolated gate drivers, they're great value parts! You can push several MHz across the isolation barrier into a load not a problem. Only downside is a bit less stand-off voltage than the equivalent ADI parts, and when they say "moisture sensitive" they really mean it, they'll go bad quick if you don't mount them after being exposed to non humidity-controlled environment.

The ADI parts say similar on the pack but in practice it never happened to me while prototyping.

Or rather, they'll go bad when you try to mount them after too long in that environment.

They come in a tube of 9, and they have 8 on stock. So probably at some time someone ordered one, they ordered a tube of 9 from TI and put the remaining 8 on stock. :-)

TIL300, it was.

But it was TIL311 I remembered as something I had seen :-). Early 80-s I guess.

Depending on the throughput you need could you perhaps do some cheap ADC -> opto -> DAC scheme... I am not very familiar with the cheap side of MCU-s but I think there are very cheap ones with an ADC, not so sure about the DAC (those I use are precision, cost >$10, but may be there are cheaper). I suppose something like 10uS per word should be achievable but well, I am just musing.

or HCNR200, afair it pretty require calibration because the photodiodes are like +/-10% gain

Me too. ;) The TIL331 is a seven-segment LED display.

Cheers

Phil Hobbs

I'd consider using a dual isolator, with the LEDs in series, except that the usual pinouts don't physically separate the hot-side output from the cold one. It'd be OK for low-voltage floating, though.

TIL300 matching (transfer gain) is tested, the -A version had max 10% mismatch, with 25% on the run-of-the-mill parts. That probably is a production nuisance.

Well, the part is long gone anyway.

Cheers

Phil Hobbs

There are I2C isolators with 2.5kV standoff voltages, at 400kHz signaling rate I think you should be able to get close to 60kHz 16 bit data across that with some basic lossless compression like modems use

It would be interesting project to see how good you could do with the 10 bit internal ADC and some data compression on say a ATTiny85 on one side and another doing decompress and fast PWM DAC on the other with both

AD have several isolated delta-sigma ADCs that would just need a clock and a lowpass filter on the "DAC" side

Is they available for love and/or money?