[SOLVED] How to check maximum operating frequency of Optocoupler ???

[jay1691]

Hiii All,

how can we find maximum operating frequency for any Optocoupler ??
Lets take FOD3180S as an example for it. Now, from its datasheet how can i find maximum frequency applied to it as a input PWM signal.

Datasheet link for FOD3180S is given below.
https://www.fairchildsemi.com/datasheets/FO/FOD3180.pdf

 

[Venkadesh_M]

Look out for the delays

one period = rise time + ON time + fall time + OFF time

the selection is based on accuracy of your duty cycle

 

[jay1691]

hiii Venkadesh_M,

Thanks for replaying. Now is it possible to apply 5KHz PWM signal with 50 % duty cycle as a input ??
Is there any simple calculation method for calculating max applied frequency for given data of "rise time , ON time , fall time , OFF time " ???

 

[Venkadesh_M]

yeah there is a formula

for example if you want select a optocoupler your

minimum duty cycle * period >= rise time + fall time
here minimum duty cycle is not zero. it is the next possible dutycycle after 0.

in your case, you are going to use it on 50% on 5khz

200 uS > 55 + 95 ns
so not a problem

also you have to consider the rise time and fall time for power loss, if you are going to control a power switch by the optocoupler because more rise time and fall time can cause lot of power wastage. in your case its not a problem though.