#1718

Episode 1718 chip of the day
like an optocoupler but using a transformer
Be a Patron: / imsaiguy

[@patwhens]

FYI.... I love "Chip of the Day".

[@curtkeisler7623]

Me too!

[@andymouse]

Me too!

[@CrazyLabs]

Me too!

[@ChrisSmith-tc4df]

One hobbyist use case for these are to safely interface additional digital signals to ESP32-based IoT WiFi AC switches that ride the power line for economic simplicity.

[@rahulkushwaha9500]

"everybody loves chip of the day". teardown the chip and see the actual transformer inside.

[@willthecat3861]

not everybody... but, I can't help watching.

[@danman32]

The diagram says functional diagram so might not have actual transformers

[@policyprogrammer]

I used one of the ADuM chips in an AC power measurement project, where the ADC chip was floating on the AC side and I wanted to communicate via SPI with it with a uC isolated from it. The chip I used actually had an isolated DC / DC converter built in, which was awesome because I didn't have to do anything fancy to power chip on the AC side. It was a lovely solution to a trickiesh problem. EDIT: actually in the final design I used a similar TI part: The ISOW 7841. The ADum 5411 which had similar specs was not available or too pricey at the time.

[@davidjones9730]

Love Chip of the Day, and appreciated the Dylan reference too!

[@leonerduk]

I bought a few of those boards on eBay a while ago. The cost of each board was cheaper than the bulk cost of getting genuine ADuM1201 chips from somewhere reputable like Mouser, so I suspect those boards use clone chips that might not live up to the full specs claimed on the data sheet. At least, if I was going to try to put 2kV across it I'd want to make sure it's the real deal ;)

[@Mr.Leeroy]

The ones I got has almost completely square package, but does not look laser etched. The same PCB otherwise. Looks like there might be some CN analog IC, and ofc you could never be sure about characteristics compared to genuine parts, especially terra-ohms level isolation.

[@TheStuffMade]

It's very useful e.g. if you're designing some kind of acquisition system, maybe measuring 3 phase voltage and current of each phase then you can have all the ADC isolated with DCDC converters plus something like this chip for the serial data. I believe they also have higher bandwidth version designed for USB isolation.

[@TheStuffMade]

@@ralfstocker7742 That's a good solution for low bandwidth, but if you need the full USB2 480Mb/sec then you'll have to get one of the dedicated chips like the ADuM4165.

[@stamasd8500]

Pretty much required in any medical application for data acquisition. To get one of those certified you have to have complete electrical isolation of any part that touches a human being, from any part that may be plugged into the wall power or exposed to any other source of dangerous voltage.

[@pukkimi]

I ordered some of those as samples when they were released, but as usual, they are still sitting in the parts drawer. Not sure what I was going to do with those back in the day, but might be usefull some day. Not going to throw them out :)

[@airmann90]

Story of my electronics life. Lol

[@emir4707]

maybe usable on adc isolation for extreme resolutions like 24bit

[@jercos]

1200 vs. 1201 being more or less "functional" I don't know... if you use them together in a pair, you have a nice isolated SPI interface. ;-)

[@leonerduk]

If you wanted isolated SPI you'd use the 4-channel variant; the 1401 has 3 out, 1 in.

[@frankowalker4662]

Neat. I've never even heard of these. 👍

[@ats89117]

I love things that are the same only different!

[@t1d100]

Maybe do a USB isolator, for comparison? IIRC, you said the voltage amplitude is limited to CMOS. If there was a similar isolator chip that could handle more volts, I wonder if it could be used to DIY an isolated/differential scope probe?

[@bob_mosavo]

Thanks 👍

[@christopherjackson2157]

Neat.

[@Jens.Peter.Nielsen]

Also, ADUM4160 / ADUM3160

[@jimomertz]

Is there really a transformer in there? Or just the electrical equivalent?

[@ChrisSmith-tc4df]

There’s a chip scale micro planar transformer formed by an etched concentric circle “winding” overlayed with SiO2 (glass) layer with another etched concentric circle “winding”. It operates at microwave frequencies.

[@jercos]

What's the electrical equivalent of a transformer, but not a transformer? Capacitive isolation is used in some chips, but I wouldn't call that "equivalent".

[@mc.the_machine]

It seems to me an electronic that would be useful to stop calling the base negative power supply voltage "ground."it seems like the term like "0v negative" would be better, "base negative," or just "base supply" might be helpful. Many modern circuits simply aren't grounded at all, so it's a bit of a misnomer to use the term, and, as this illustrates, there are logical reasons sometimes where when circuit's base negative voltage might not be most sensibly the same as another, even if it's connected. For example, with what you just showed about power differential, there may be reasons why it's simpler to have a regulated supply for one part of a circuit where the negative voltage is floating compared to another one. If the two circuits both have their negative supply marked as ground, it gives a misleading, and potentially dangerous or damaging assumption that the grounds could be linked together and, apart from ground loops, behave the same.

[@michaelsouth2567]

On the other hand, seeing something labeled "ground" is a big red warning that the manufacturer has not made any efforts to isolate the circuit and you should assume it is, in fact, tied to a common earth. Think your SBC (Arduino, Pi) "ground" pin is isolated because you're feeding it from a wall wart, or even a battery? Nope--it's tied to earth through the HDMI cable's ground, via the monitor. Or your nice high-quality, transformer-isolated wall wart has a mains ground pin and ties its output ground to it. You'll notice in the video that the Rigol supply does, in fact, have separate low-side jacks for each output, they're labeled "minus" instead of "ground", and there's another jack labeled "earth". So they're isolated. (Though I wouldn't trust an inexpensive supply without measuring it.)