If I have a pair of I2C traces (SDA and SCL) on a 1 oz board, each being 8mil wide and separated by an 8mil gap, how long would the traces have to be before crosstalk would become an issue?
Edit:
Apologies for not making this clear before, but I was asking from a theoretical point of view, and with everything else considered equal.
I was checking the rise times on an I2C bus, and the crosstalk spikes were larger than I would have expected (300-400mV).
After reading some of the replies, I measured the fall time – it's about 15nS, and from my calculation I must have about 80pF of capacitance on the bus.
Best Answer
Crosstalk is usually not a problem, when the I2C bus is contained within a single PCB and pull-up resistors are properly sized. As the size of the bus grows, bus capacitance will become a problem before crosstalk becomes a problem.
If you think that capacitance between SDA and SCl is high, run a grounded trace between them.
(Source)