I am using 6N137 opto-isolator for my circuit.
I have attached schematic for the same. I am giving Input and Enable from SMPS as shown and ground is same. VCC and EN is 3.3V from SMPS.
But while checking output voltage when Input and EN is High ( VCC is also High ie 3.3V ), I am getting Logic High at output (3.3V).
Ground for both is same.
Link for datasheet : http://www.vishay.com/docs/84732/6n137.pdf
Can anyone help me for above issue.
Thanks in advance.
You should hew to the datasheet recommended minimum voltage of 4.5VDC if you want reliable operation, however it does not appear that is the proximate issue.
Your measurement of +5V at 2 and 0V at 3 indicates you have a wiring problem or you've damaged the LED (perhaps by accidentally connecting it without a resistor for even an instant). The LED forward voltage should be around 1.3-1.6V- and that is a good indication that it is actually emitting light. If it is much less or much more, that indicates a short somewhere (perhaps internally) or an open (again, perhaps internally). In your case it appears to be open.
As an aside, your 200 ohm resistor is a bit on the low side- I suggest keeping the nominal current more like 10mA. That is not what damaged the LED (if that's the problem) just better for long-term reliability.
According to datasheet, minimum supply voltage VCC is 4.5V. Change the voltage if you can and test it again.
