USB 3.0 Hub Design Guide
© 2015 Genesys Logic, Inc. - All rights reserved.
Page 17
GLI Confidential
2.6
Power Trace of Charging Downstream Port
USB3.0 Hub allows BC1.2 portable device draw 1.5A from each charging downstream ports (CDP) by
compliant with USB Battery Charging Specification rev1.1, so
the width of charging downstream port VBUS
trace is better to > 60mils
to support enough current to avoid voltage drop
.
And the total adapter or system
power source should also consider how many CDPs support to provide enough current for fast charging. For
example, if the design supports four charging downstream ports, the 5V power supply must be capable of
delivering total 6Amps.
2.7
Thermal Reduction
Optimum layout suggestion for thermal sensitive design: The copper under chip GND area is through via
holes and inner 2 (GND layer) to reach heat sink effect.
Figure 2.15
To prevent temperature surge on silicon surface under worst environment, it is strong recommended to use
following layout option to increase the efficiency of silicon heat spreading. The copper under chip GND area
must be appeared on bottom layer and drill more through holes (0.5mm) to reduce chip thermal impact.
Top View Bottom View
Chip ground VIA
Diameter ─ 0.5mm
VIA to VIA gap ─ 50 mil