Linear Optocouplers (Patreon)

Isolating the 3 OSMU output channels has a ton of advantages. They can be connected in series for higher voltages or in parallel for higher current for example.

But communicating with these isolated channels isn't easy. They need to know what voltage and what current they can put out, and they have to report back the actual values of the two parameters.

That's at least 4 analog values that have to be transmitted over an isolation barrier with a high bandwidth and no delay ideally.

After multiple less-than-ideal attempts, this is my latest idea: IL300 linear optocouplers.

Basically they contain an LED and 2 equal photodiodes. An op amp can used to drive the LED to a desired analog 'brightness' based on feedback from the first photodiode. The second photodiode puts out an equal voltage on the far side of the isolation barrier.

No delayed digital conversion and a bandwidth > 200 kHz. The components are small and reasonably priced, at least in the wider tolerance grades (which will be fine, because the thing has to be calibrated anyway).

I think these are very promising, but the idea is from pre-FPGA times. If I really go down the FPGA route, a few new options are unlocked, like isolated LVDS or multiple high speed SPI busses ...