regards,
Larry Smith
Sun Microsystems
> From: Vigliarolo Roberto <Vigliarolo@asamrt.interbusiness.it>
> To: "'Larry Smith'" <ldsmith@lisboa.eng.sun.com>
> Cc: si-list@silab.eng.sun.com
> Subject: Re: [SI-LIST] : Surface Mount Cap Lead Inductance
> Date: Wed, 12 Aug 1998 10:47:41 +0200
> X-Priority: 3
> MIME-Version: 1.0
> Content-Transfer-Encoding: quoted-printable
>=20
> =09Sorry fom my message being late but I live in Europe and as you
> now there is
> =09at least 6h time difference between here and the USA....
> =09I agree with you all but it seems to me that the original
> question from Mike Mayer=20
> =09was related to SMD tantalum caps (7343, 6032, etc.) and my
> understanding is that
> =09their ESL is higher than the ESL of ceramic cap (1 to 3 nH: see
> for an example=20
> =09page 25 of Kemet catalog F-3102B 2/97) and so it is of the same
> order of the=20
> =09layout inductance.
> =09Of course you have to consider that the resonance you obtain is
> damped by the=20
> =09relatively high ESR of tantalum caps and so it is difficult to
> have probelms with=20
> =09resonances associated with tantalum caps.
>=20
> > ----------
> > Da:=09Larry Smith[SMTP:ldsmith@lisboa.Eng.Sun.COM]
> > Risposta a: =09Larry Smith
> > Inviato:=09marted=EC 11 agosto 1998 19.07
> > A:=09Vigliarolo@asamrt.interbusiness.it; raymonda@radium.Eng.Sun.COM
> > Cc: =09si-list@silab.Eng.Sun.COM
> > Oggetto:=09Re: [SI-LIST] : Surface Mount Cap Lead Inductance
> >=20
> > Tanmoy Roy, John Prymack and myself will be presenting a paper
> > in October at the EPEP conference that goes into a little more
> > depth on the mounted inductance of decoupling capacitors. We
> > find that there are 3 major contributers capacitor inductance:
> >=20
> > =09pad and via design=09=091.00 to 4.00 nH
> > =09plane spreading inductance=090.01 to 0.50 nH
> > =09capacitor height=09=090.20 to 0.40 nH
> > =09
> > The three components sum together. Inductance is essentially a
> > measurement of the flux or B field in the environment caused by
> > current going around a loop. The bigger the loop, the more the
> > flux and the more the inducance. =20
> >=20
> > As Ray stated below, the pad and via design are the most important
> > contributers to capacitor inductance. The design of the power planes
> > (PCB stackup) is second in importance. Third in importance is the
> > capacitor height. If the capacitor manufacturer has compensated out
> > the first two contributors to inductance (given you the self
> > inductance of the capacitor) the third (and least important) part is
> > all you get. Inductance numbers quoted for surface mount devices
> > are often mis-interpreted or mis-understood.
> >=20
> > Come to the EPEP in West Point NY on October 26-28 and get the
> > rest of the story!
> >=20
> > regards,
> > Larry Smith
> > Sun Microsystems
> >=20
> >=20
> > > Date: Tue, 11 Aug 1998 09:17:13 -0700 (PDT)
> > > From: Ray Anderson <raymonda@radium.eng.sun.com>
> > > Subject: Re: [SI-LIST] : Surface Mount Cap Lead Inductance
> > > To: Vigliarolo@asamrt.interbusiness.it
> > > Cc: si-list@silab.eng.sun.com
> > > Mime-Version: 1.0
> > >=20
> > >=20
> > > =09You will probably find that the ESL of the capacitor
> > > is only a small part of the "mounted inductance" of the part
> > > when it is placed on a PCB. A larger percentage of the total
> > > loop inductance that your circuit sees associated with a mounted
> > > capacitor comes from the following factors:
> > >=20
> > > =091=09Pad Geometry
> > > =09=09=09connector traces
> > > =09=09=09via location
> > > =09=09=09Number of vias
> > > =09=09=09
> > > =092=09Stackup
> > > =09=09=09distance from mounting pads to power planes
> > > =09=09=09
> > > =09All those factors that influence the loop area seen by the
> > current
> > > flowing through the capacitor influence the mounted inductance. The
> > amount=20
> > > contributed by the capacitor is a small part and is usually
> > overwhelmed by=20
> > > the other constituents unless you do a VERY good job in minimizing
> > the other=20
> > > contributions (which can be done). The ESL of the capacitor by
> > itself is a=20
> > > very strong function of the height dimension of the part.
> > >=20
> > > =09It is the mounted inductance of a bypass capacitor that mostly=20
> > determines
> > > the effectivness of the bypassing that the part provides.
> > >=20
> > >=20
> > > Ray Anderson
> > >=20
> > > Sun Microsystems Inc.=09=09
> > >=20
> > >=20
> > >=20
> > > > From: Vigliarolo Roberto <Vigliarolo@asamrt.interbusiness.it>
> > > > To: si-list@silab.eng.sun.com
> > > > Subject: Re: [SI-LIST] : Surface Mount Cap Lead Inductance
> > > > Date: Tue, 11 Aug 1998 17:55:15 +0200
> > > > X-Priority: 3
> > > > MIME-Version: 1.0
> > > > Content-Transfer-Encoding: quoted-printable
> > > >=20
> > > > You can easily calculate the ESL of your capacitor by looking at
> > the
> > > > frequency of the dip in the impedance vs frequency chart usually
> > > > provided by capacitors manufacturer.
> > Fresonance=3D1/(2*pi*sqrt(ESL*C))
> > > >=20
> > > >=20
> > > >=20
> > > > > ----------
> > > > > Da:=09Mike Mayer[SMTP:Mike.Mayer@heurikon.com]
> > > > > Inviato:=09luned=EC 20 luglio 1998 22.40
> > > > > A:=09si-list@silab.Eng.Sun.COM
> > > > > Oggetto:=09[SI-LIST] : Surface Mount Cap Lead Inductance
> > > > >=20
> > > > > I was looking at a note from howard Johnson about decoupling
> > ("Bypass
> > > > > Multi-Valued Arrays"):
> > > > >=20
> > > > > http://www.sigcon.com/news/1_17.htm
> > > > >=20
> > > > > I started looking into it but can't seem to find any information
> > on
> > > > > lead inductance for surface mount packages, especially the types
> > used
> > > > > by tantalum caps (7343, 6032, etc.). Has anyone seen a source
> > for this
> > > > > information?
> > > > >=20
> > > > > --=20
> > > > >
> > =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D
> > > > > =3D=3D=3D=3D=3D=3D=3D
> > > > > Mike Mayer Artesyn Communication
> > > > > Products, Inc
> > > > > Madison, WI
> > > > >
> > http://www.artesyn.com/cp
> > > > >
> > =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D
> > > > > =3D=3D=3D=3D=3D=3D=3D
> > > > >=20
> >=20