how is maximum operating frequency calculated???

[biswaIITH]

i have a question ..

How to calculate the maximum operating frequency at which any optocoupler is operated???

i saw in one post of where the following rule is mentioned...

minimum duty cycle * period >= rise time + fall time

if we take TLP350 for example if i want to operate it at 100Khz ,the above condition satisfies..(rise time and fall time being 15 and 8 ns respectively)

But, in the datasheet of TLP350 the operating frequency is given as 50Khz...

 

[Truedeal]

To find out take a component and wire it in to a circuit board and run your test and come to your own conclusions. If the signal is not distorted at 100 KHz and it does not latch up, over heat, or quit responding you have your answer. Be aware that various batches will respond differently. Most manufacturers have a specification window they aim for. The 50 KHz response is the minimum they will accept.
Solid state relays are the same way.

 

[biswaIITH]

Thanks for your reply...but i am curious whether any mathematical relation exists between different times(i.e. rise time,delay time,fall time) and maximum switching frequency attainable

 

[chuckey]

From my reading of an incomplete Toshiba data sheet for this device, the output current is 1A, I would guess that this reduces at higher frequencies. Likewise the test for the LED drive current is done with 1 microsecond pulses at a rate of 300PPS. So you can have lots of current or high(ish) speed.
Frank

 

[Anna Conda]

The 50kHz rating is related to the power in the output devices on this part - the datasheet says refer to note 3 which specifies the currents, no doubt you can run it faster if you buffer the output or are running into light loads, best to test on the bench with a sig-gen and a range of loads, including capacitance to simulate the devices you are driving...