Likely value of Cpole for optocoupler?

[grigson]

hello

do you know what are likely values of the Cpole parameter for this optocoupler?

CNY17-2

http://www.vishay.com/docs/83606/cny17.pdf

I am talking about when there is round 3mA flowing in the opto diode.
I need the full tolerance range....i.e min and max of Cpole.

This optocoupler will be used with the opto transistor in common emitter connection in an SMPS feedback loop.

We must absolutely know this Cpole value and its tolerance range because our SMPS output LC filter (EMC filter) has a resonant frequency of 8KHz, and we must arrange our smps loop crossover frequency to be at least three times less than this or else we will get output filter interaction and instability.

As you know, Cpole is a parameter which determines the crossover frequency.

The manufacturer wont tell us the data.

 

[MacGyverS2000]

Have you tried measuring it?

Dan - Owner

http://www.Hi-TecDesigns.com

 

[grigson]

We understand how to measure it, its just that part to part variance is said to be extremely wide, and if we measure it on one part, we've still no idea what is the min and max of any particular batch.

We are in Vancouver and the semiconductor/component reps dont get up to us much too.

 

[MacGyverS2000]

Then you understand the problem, so asking us to provide you with a value will be an exercise in futility. The manufacturer won't give you a specific value (or even a tight range) because they know one doesn't exist unless you enjoy binning. We won't have any better luck than you would, but at least you're getting paid to do the work.

Figure out what range of values you can handle... Monte Carlo may be a way to go here if multiple components affect the overall value. If that range of values is smaller than what the component offers, then you may need to bin or rearrange your circuit to compensate.

Dan - Owner

http://www.Hi-TecDesigns.com

 

[VEBill]

This app note seems to have some useful tidbits.

http://www.ti.com/lit/an/snva005a/snva005a.pdf