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04-15-2017 05:51 AM
Most of the Manufacturers use Low pass RC filters in the data lines of USB pins & also in GPIO pins. some of the manufacturers connect resistor to micro-controller pin first & then capacitor & some manufacturers connect Capacitor first then resistor (Please go through the attachments). so what is the standard one to follow in the designing.
Solved! Go to Solution.
04-17-2017 03:09 AM - edited 04-17-2017 03:09 AM
There is no standard one to follow, as there are subtle differences in the µCs and application PCBs. Most modern USB µCs do not need the external transistor that the NXP LPC µCs require for USB soft connect.
But USB 2.0 full speed is rather forgiving at 12 MBit/sec, so just look at the schematic of an STK or DK for the USB port and you are good to go.
04-17-2017 10:23 PM
I agree with @Turbo_J.
I think basically maybe external component was added for the purpose to ESD protection and impedance matching.
We have an application note AN203 to address the consideration need to take for ESD protection purpose, I am not sure if it helps.
For the GPIO output mode, as the picture indicated, it should be avoided to add a big value capacitor to avoid too high current flow when the GPIO toggle.
My views are my own and do not necessarily represent the views of Silicon Labs