EMI and noise issues

AN4356

4/14

DocID025260 Rev 1

Figure 4 shows the differential signals D+ and D- on a USB2.0 link where 150 ps of skew

occur at 480 Mbps.

Figure 4. Noise brought by skew on a USB2.0 link in time domain: D+ and D- with

150 ps skew

Figure 5 shows the common mode signal [D+] + [D-]. We can observe that its level is not

negligible.

Figure 5. Noise brought by skew on a USB2.0 link in time domain: Common mode

signal [D+] + [D-] noise introduced by skew

VPP = 400 mV

VPP ≈ 70 mV