Microcontrollers communication via opto-coupler

[eem2am]

If two mirocontrollers either side of a 3.5KV isolation boundary wish to communicate by CNY17-3 optocoupler
-what max frequency can they communicate at?

CNY17-3 datasheet:
https://www.fairchildsemi.com/ds/CN/CNY173M.pdf

 

[hakeen]

Hi

CNY17 is a phototransisotr output optocoupler. Theyoretically they can do up to few tens of kHz. But practically they will be around 5-10kHz range (depending forward current, pull-up resistor and load capacitance).

If you are concerned speed depends on insulation (not isolation) voltage, then you should not. You ought to think insulation parameter is directly related to internal clearance of package. However this distance is very small compared to speed of light. Thus it does not cause any signifcant delay. If I am not worng CNY17s have 0.4mm internal distance.

As a last point I would like to say if you are working on an industrial project, I would recommend using a real digital optocoupler. Maybe somehting like ACPL-M50L. It has very low pwoer consumption (LED can be driven as low as 3mA and Icc2 max 100uA. It is less exprensive than equivalent class, however compartively more expensive than CNY17.

Avago's ACPL-M50L (single channel) are low power, low-input current, high speed digital optocouplers in SO-5 footprint.

Hope helps

Cheers