[SI-LIST] Re: How to place the AC coupling capacitor of the serdes?

LIU=20Luping,

This=20was=20recently=20discussed=20here=20at=20length,=20here=20is=20a=20=
brief=20summary=20for
PCI=20Express=20application:

PCI=20Express=20Base=20Specification=20section=204.3.1.2=20calls=20out=20"=
The
requirement=20for=20the=20inclusion=20of=20AC=20coupling=20capacitors=20on=
=20the
interconnect=20media=20is=20specified=20at=20the=20Transmitter",=20but=20t=
here=20are=20no
specific=20placement=20rules=20except=20the=20specifications=20for=20separ=
ate=20host=20/
card=20module=20require=20that=20physical=20division.=20Based=20on=20the=20=
recent=20"AC
Coupled=20Signals"=20thread,=20it=20would=20seem=20reasonable=20to=20place=
=20the
capacitors=20at=20the=20receiver=20on=20a=20system=20board,=20allowing=20t=
he=20advantage
that=20the=20mounting=20pads=20could=20be=20used=20for=20probing=20-=20eli=
minating=20the
necessity=20of=20separate=20test=20points=20at=20the=20RX=20end.=20This=20=
is=20agreed=20by
consensus.

-Ivor


-----Original=20Message-----
From:=20si-list-bounce@xxxxxxxxxxxxx=20[mailto:si-list-bounce@xxxxxxxxxxxx=
g]
On=20Behalf=20Of=20liuluping=2041830
Sent:=20Thursday,=20January=2017,=202008=208:11=20PM
To:=20si-list@xxxxxxxxxxxxx
Cc:=20oukanghua@xxxxxxxxxx
Subject:=20[SI-LIST]=20How=20to=20place=20the=20AC=20coupling=20capacitor=20=
of=20the=20serdes?

Dear=20si-listers:
AC=20coupling=20per=20the=20PCI=20Express=20Base=20Specification=20Revisio=
n=201.0a,
section=204.3.1.2=20dictates=20AC=20coupling=20to=20be=20placed=20as
close=20as=20practical=20to=20the=20transmitter=20buffer.=20
We=20consider=20that=20the=20AC=20cap=20is=20used=20to=20ensure=20the=20DC=
=20bias=20levels=20of=20the
transmitted=20signal=20do=20not=20adversely
affect=20the=20receiver,and=20most=20of=20time=20place=20it=20clsoe=20to=20=
the=20receiver
side.Why=20the=20PCIe=20requires=20=20to=20put=20it=20on=20the=20TX=20side=
?
Is=20it=20differ=20from=20different=20serdes=20interface?

=20Thanks=20and=20Regards,

=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20LIU=20Luping



_______________________________________________________________________
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