Optically isolated channels for SPI

[Omar]

Hi 😊
I'm currently working on graduation project that  includes battery management system and it will be 48 v....
So 13 lithium Ion cells will be connected in series...
And i have to monitor every individual cell voltage and temperature 😭😭...
I would go with mcp3008 ADC to do that task ....
But the problem is that every ic will monitor 4 cells and it will be at higher voltage above the main processor...
I mean that zero volt and 5 v of digital signals will be higher than the main processor by 20 and 36 v ....
I have an idea of creating 4 optically isolated channels for SPI communication protocol.........
The question is ...
Is that possible???
Did you see something like that before???
Is there a better solution???

[David Hess]

SPI is one of the easier interfaces to optically isolate because all of the signals are one way with clock output, data output, data input, and select if needed.  And since logic level signals are used, the same circuits used to isolate logic level signals can be used with SPI.

Vishay suggests using logic level optocouplers but any transistor optocoupler can be used as well.

[MasterT]

Not necessarily "optical" - galvanic isolator , or digital isolator. There are many,
https://www.mouser.ca/c/semiconductors/interface-ics/digital-isolators/
Or you can use Isolated ADC
https://www.mouser.ca/c/semiconductors/data-converter-ics/data-acquisition-adcs-dacs-specialized/?product=Isolated%20Analog%20to%20Digital%20Converters

[Benta]

Look at the TI series of ISO7xxx digital isolator IC's. Cheaper and easier.
This one's made for SPI:
https://www.ti.com/product/ISO7041

[ajb]

Thirding the digital isolator suggestions, they're a much better solution than actual optos for applications like this.  They're available in varying channel count/direction combinations, so it's pretty easy to get a single part that will isolate all of the channels you need in the correct directions for most common applications.