Gecko G320 tech question

[bharbour]

Can anybody tell me what the input capacitance value seen looking into the encoder inputs on a G320 drive will be?

I am working on implementing the optical isolation I mentioned in my previous post on the G320 system and need an estimate of the input capacitance.

The optocouplers I got have open collector inputs and I want to get an idea of the rise-times I will get with the resistor pullup I am using.

Is the simple circuit shown in the version 7 of the manual a good enough approximation or is there an RC input filter on these pins that will kill me? What chip/circuit is it actually driving?

Thanks,
Bob

[Mariss Freimanis]

The input is as drawn; a 1K pull-up to 5VDC going directly into a CD4093 input. Call it 20pF when taking parasitics into account.

Mariss

[bharbour]

The input is as drawn; a 1K pull-up to 5VDC going directly into a CD4093 input. Call it 20pF when taking parasitics into account.

Mariss

Thanks, that was just what I was hoping for!

BobH