Epson S2R72A21 Application Note page 30

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Chip varistor
Use on the DP/DM signal line can be effective in protecting the S2R72A21's DP/DM pins from static electricity
and surges. Typical components used for USB High-speed are listed below. Note that components should
preferably be installed with shortest possible branches from the signal line to ensure signal quality. The chip
varistor mounting position is generally considered more effective in the vicinity of the connectors, but this should
be determined after consulting with the respective manufacturers.
•
TDK
•
Panasonic
•
Connector
The DP/DM signal quality may deteriorate if a non-USB certified connector is used. It is recommended that
USB-certified connectors be used. The same applies to the cables used.
•
Connection example of additional components
Receptacle
Figure 7.2.2.3
Remarks：
In case when you add some capacity components such as Chip varistor and etc. on the DP/DM signal line, the
rising / falling (Tr/Tf) characteristic of the USB HS transmit waveform would be rather gentle. If the capacity
component is large, there would be a possibility that the USB compliance test (Tr/Tf characteristics, eye pattern
test and etc.) would fail. So please take care of selecting the components.
28
Common mode choke coil
Figure 7.2.2.1 Typical common mode choke coil wiring
AVR series
EZJZ series
Valistor
Figure 7.2.2.2
Common mode
choke coil
DP
DM
Valistor
Connection example of additional components
Seiko Epson Corporation
DP line
DM line
DP line
DM line
Typical varistor wiring
INT_DP/EXT_DP
INT_DM/EXT_DM
S2R72A21
S2R72A21 Application Note
(Rev.1.00)