HD3SS3220_15 Datasheet, PDF (35/43 Pages) Texas Instruments – HD3SS3220 USB Type-C DRP Port Controller with SuperSpeed 2:1 MUX

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HD3SS3220
SLLSES1 – DECEMBER 2015
To minimize the discontinuities associated with the placement of these components on the differential signal
traces, TI recommends partially voiding the SMD mounting pads of the reference plane by approximately 60%
because this value strikes a balance between the capacitive effects of a 0% reference void and the inductive
effects of a 100% reference void. This void should be at least two PCB layers deep. For an example of a
reference plane voiding of surface mount devices, see Figure 20.
SIGNAL TRACE
SMD
SMD
VOID
PAD
PAD
SIGNAL TRACE
Figure 20. Reference Plane Voiding of Surface-Mount Devices
10.1.8 ESD/EMI Considerations
When choosing ESD/EMI components, TI recommends selecting devices that permit flow-through routing of the
USB differential signal pair because they provide the cleanest routing. For example, the TI TPD4EUSB30 can be
combined with the TI TPD2EUSB30 to provide flow-through ESD protection for both USB2 and USB3 differential
signals without the need for bends in the signal pairs. For an example of flow-through routing, see Figure 21.
USB 3.0
Host Controller
Figure 21. Flow-Through Routing
8 mm
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