[SI-LIST] Re: Integrated vs. discrete magnetics for Ethernet

The main benefit of external is that you get to choose the common mode
choke, and it will have a lot more iron (read attenuation) than the puny
:-) little thing inside the RJ-45. When I worked for a telecom
manufacturer we always used external. However, the small footprint
boards we make here require the integrated jacks, and we have made them
work. As noted below, you need to be extra careful keeping your signal
clean into the transformer ....

                                                Curt

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-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx]
On Behalf Of Chris Padilla (cpad)
Sent: Tuesday, February 28, 2006 12:11 PM
To: si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Re: Integrated vs. discrete magnetics for Ethernet


Prakash,

Most of my experience is with Broadcom and Marvell Phys.  They both are
wonderfully robust parts but a side effect of that robustness (which
comes from their DSP), is higher harmonic noise:  Namely the 125 MHz
harmonics all the way to 1 GHz can be troublesome.

I have mostly dealt with 2x6 (6 over 6) and 2x8 (8 over 8) IntMags to
the tune of 48 ports as we are always trying to maximize port density.
That is a lot of DSPs pumping away through the fairly (electrically)
large cavities within the shielded jacks.  Trying to pass Class A can be
difficult!  How many ports did you have, Charles? :o)

There is no way I can compress 6 years of experience on these parts into
a simple reply here.  As has been repeated ad naseum on this list, it
depends on so many factors: stack-up, board routing, part selection,
chassis design, etc.

In my experience, I don't think it matters much if you go discrete or
integrated.  Board real estate is often a very precious commodity
HOWEVER:

With discrete, you have a great deal of "access" to play with and tune
parts.

With integrated, you must rely on the manufacturer of the part (Pulse,
Bel, etc.) to tune things for you.

Make no bones about it, going discrete or integrated, without a good
deal of forethought and experienced leadership, it could be difficult in
the chamber passing a great number of ports.

All that said, integrated magnetic RJ45s are a relatively mature product
for the big boys like Pulse and Bel and so they have a good deal of
experience to help you with the design of the board: use them!  Find out
how much support you can expect from them.  Personally, I would lean
towards Bel but Pulse is good as well.

Good Luck!

Chris Padilla
Cisco Systems
San Jose, CA=3D20

-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx]
On Behalf Of Grasso, Charles
Sent: Tuesday, February 28, 2006 7:58 AM
To: jswarrier@xxxxxxxxx; si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Re: Integrated vs. discrete magnetics for Ethernet

Well I suppose this is another case where "it depends".
We have a system with an Ethernet integrated magnetics that passed with
>10dB of margin to ClassB with the ENet running at full bore.

Now - we only use one connector...anyone from Cisco and involved in EMC
on this list care to comment??

Best Regards
Charles Grasso
Senior Compliance Engineer
Echostar Communications Corp.
Tel: 303-706-5467
Fax: 303-799-6222
Cell: 303-204-2974
Pager/Short Message: 3032042974@xxxxxxxx
Email: charles.grasso@xxxxxxxxxxxx;
Email Alternate: chasgrasso@xxxxxxxx

-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx]
On Behalf Of Jai Shanker
Sent: Monday, February 27, 2006 10:34 PM
To: si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Re: Integrated vs. discrete magnetics for Ethernet


Its probably LXT PHYs from Level One that Intel has used in its previous
chips and not Marvell.

I think the jacks come in different versions with
1:1.25 or 1:1 ratios as required for different PHYs.
We used the integrated jack in a prototype but didnt go for any EMC
compliance tests so I have no further info on this.

regards,
Jai

--- "Chauhan, Prakash" <pchauhan@xxxxxxxxxxx> wrote:

> This is an Intel PCI Express based Gigabit Ethernet  Controller. =20
>The=3D20 Phy  is integrated.  I think Intel had integrated  Marvell's =
Phy

>on=3D20 some chips  in the past, but I don't know whether this device =
is=20
>=3D20 different. =3D3D3D20 =3D3D20  Thanks,  Prakash.=3D3D3D20 =3D3D20  =

>-----Original =3D

>Message-----
> From: Chris Padilla (cpad)
> [mailto:cpad@xxxxxxxxx]=3D3D3D20
> Sent: Monday, February 27, 2006 1:20 PM
> To: Chauhan, Prakash; si-list@xxxxxxxxxxxxx
> Subject: RE: [SI-LIST] Integrated vs. discrete  magnetics for Ethernet

>=3D3D20  Tell us what Phy vendor you are planning to use:  Marvell or=20
>Broadcom or  ???
>=3D3D20
> Chris Padilla
> Cisco Systems
> San Jose, CA=3D3D3D20
>=3D3D20
> -----Original Message-----
> From: si-list-bounce@xxxxxxxxxxxxx
> [mailto:si-list-bounce@xxxxxxxxxxxxx]
> On Behalf Of Chauhan, Prakash
> Sent: Monday, February 27, 2006 10:00 AM
> To: si-list@xxxxxxxxxxxxx
> Subject: [SI-LIST] Integrated vs. discrete magnetics  for Ethernet =3D
=3D3D20

>Hi All,
>       I was wondering if anyone has comments regarding  the use of =3D20

>integrated magnetics (In the RJ-45) versus a  discrete implementation=20
>=3D20 (for 10/100/1000 Base-T).  I have been advised that  =
integrated=3D20=20
>magnetics  have poorer shielding (between diff pairs) and can  be=3D20=20
>problematic from  an EMC compliance standpoint.  I would much prefer=20
>=3D20 to use integrated  Magnetics for space conservation and to have=20
>less =3D20 component count and  simplify layout.  If anyone has had=20
>problems with

>the Integrated  Magnetics I would love to hear about it. (I am =3D20=20
>planning on using Belfuse  Magjack family part:  0826-1X1T-23-F). =20
>Any=3D20 appnotes  that can help  implement this from a compliance=20
>standpoint=3D20 would be  greatly  appreciated. =3D3D20
> Thanks,
> Prakash.
>
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