USB 3.0 Hub Design Guide
© 2015 Genesys Logic, Inc. - All rights reserved.
Page 15
GLI Confidential
2.4.3
Crystal Circuit
1.
50ppm precision class is recommended for the X’tal.
2.
Keep the distance between crystal and the IC less than 1cm to avoid triggering high frequency oscillation on
PCB. If over 1cm is unavoidable in the design, place the capacitors and the resistor as close as possible to
the IC. Recommend less than 1cm if possible. And the resistor need be between the IC and the capacitor. See
Fig. 2.12
Figure 2.12
3.
Do not route X1 and X2 underneath the IC. In this case, it may cause noise on PCB and will trigger high
frequency oscillation.
4.
The crystal traces shall be symmetrical and parallel in order to get better oscillation wave form and better
EMI protection (as shown in
Fig. 2.13
).
Figure 2.13
2.4.4
Reset Circuit
Keep the Reset circuit placement as close to the IC as possible.