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A question about 6N137

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mertkan65

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Hello Friends,

When I was searching the topics I found an old topic about "Optocoupler delay" () I have been designing ADC/DAC card with SPI bus, I have 6N137 samples at stock, thus I want to use them for the design. This is my first design experience:) I have designed a circuit for 6N137 but I am not sure about it. I am sending circuit diagram as an attachment, I will be very appriciated if you give me some suggesiton about this circuit.
 

You have a /CS1 signal connected to the Anode and this notation is used to signals which are active LOW ..
Wouldn't be better if you connected the Anode through 680Ω to "left side"+V and the /CS1 signal to the Cathode .. this will disconnect ground on both sides of the optocoupler and will provide expected isolation of both sides ..
On top of that, an active "L" signal on the left side will generate "L" signal on the right side ..

Regards,
IanP
 
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IanP said:
You have a /CS1 signal connected to the Anode and this notation is used to signals which are active LOW ..
Wouldn't be better if you connected the Anode through 680Ω to "left side"+V and the /CS1 signal to the Cathode .. this will disconnect ground on both sides of the optocoupler and will provide expected isolation of both sides ..
On top of that, an active "L" signal on the left side will generate "L" signal on the right side ..

Regards,
IanP
Click to expand...

Thanks for your suggestion IanP :wink: As I said I am not sure about my design. I want to design noninverting circuit (an active "L" signal on the left side will generate "L" signal on the right side) as you said. I think you are right about your suggestion.

Meanwhile, what do you think about R values on the right side and on the left side?
 

From the 6N137 data sheet:
A maximum input signal of 5 mA will provide a minimum output sink current of 13mA (fan out of 8).
Click to expand...

In your case the output resistor at Vcc = 5V will allow ≈7.4mA, what is withing quoted range, and the input - the threshold current is 3mA - so, for 5V supply and typical Vf of 1.8V will cause ≈ 4.7mA of If - also within the range ..

Regards,
IanP
 
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That's it, mate ..

I just hope that the Vccs on both sides aren't of the same source as the whole "optocoupling" isolation wouldn't make sense any more ..
Rather name them Vcc1 and Vcc2, or something like that ..

Regards,
IanP
 

IanP said:
That's it, mate ..

I just hope that the Vccs on both sides aren't of the same source as the whole "optocoupling" isolation wouldn't make sense any more ..
Rather name them Vcc1 and Vcc2, or something like that ..

Regards,
IanP
Click to expand...

They are different source, I am aware of that but I have not decide power source yet. Maybe I can use "Isolated 2W Dual Output" NMH0515D or I can use Vcc of the STEBus.

Thanks.

Edit: Writing mistake.
 

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