Other Parts Discussed in Thread: PROFIBUS,
I had implemented the ISO1430 in our bus equipment expecting to meet the ProfiBus requirements regarding the very low connection capacitance of about 10pF to 25pF to the bus. But by bus driver circuit has failed the ProfiBus Test Scenario where the difference of over- and undershot within a test pulse periode has to be less than 10% of the pulse amplitude. In my case the spikes cover more than 40% of the pulse amplitude which indicates a much higher capacitive load. My measurement with an LCR Meter showed about 90pF. In the regarding area of my layout there should be no such high parasitic capacitance: The traces from connector to the ISO1430 are about 1 inch long, the biassing and terminating network was placed close to the ISO1430.
I did not find the capacitances for A / B pins in the datasheet. Maybe the ISO1430 contributes a relevant part of the 90pF?
