I'm trying to do some crosstalk calculations between signals and I'm trying to find the minimum rise times for the STM32F768IIT6 – all I see are the maximum rise/fall times for the specified test conditions. I've looked in the datasheet and reference manual but all I can find are maximum rise/fall times. How do I find the minimum rise/fall time? Why are these not included?
For example I have SPI traces around 35mm long going to TLC5922 LED driver. How can I calculate what my fastest rise time will be ?
Thanks in advance!
Best Answer
The minimum rise-time depends on as much on the output resistance of the STM32 as it depends on the capacitance on the wire. 35mm is not long. Just put the traces over a ground plane and you are good. If you think there could be some issues, put 10R resistors into the path (make sure that you still get a fast enough rise-time for the frequency you have chosen), but I doubt that this will be necessary.