AN3317

USB routing

Doc ID 18249 Rev 2

17/22

6.1

USB decoupling and reference resistor

Place decoupling capacitors as close as possible to the power balls (preferably directly

under the power balls) using short, wide connecting traces.

Placing decoupling capacitors at a distance degrades performance, which can result in

interoperability problems and specification compliance violations.

Table 3.

USB power, ground, and reference guidelines

Pin

Guideline

*vss*

Connect all vss pins directly to internal PCB ground plane

*vdd*

Connect all vdd pins to 100 nF capacitor under ball using short wide trace

USB_TXRTUNE

43.2

Ω resistor to ground