[SI-LIST] Re: AC/DC impedance spec for floppy and 40Pin-IDE cables.

The 40-pin cable Charles talks about is also a prime candidate for=20
problems with emissions for the constructional reasons cited. =20
Depending upon the specific application and use, this cable will not=20
likely pass FCC or CE requirements for even a Class A device.

I know you didn't ask, but that will be an eventual issue to get your=20
product to market.

Warren Birmingham
Epsilon-Mu Consultants
(510) 793-4806
email: warren@xxxxxxxxxxxxxx
website: http://www.epsilon-mu.com

On Saturday, Sep 14, 2002, at 05:12 US/Pacific, Charles Hill wrote:

>
> John,
>
> I've calculated and measured the characteristic impedance matrix for=20=

> the 40
> pin IDE cable.  The 80 pin IDE cable is a ground-signal-ground =
(mostly,
> there are a few extra grounds) configuration so each signal line is=20
> near a
> nominal characteristic impedance.  The 40 pin IDE cable has only 7=20
> grounds
> in it, with all 16 data lines together without any grounds inbetween. =20=

> In
> terms of the RLGC matrices, there is a lot of inductive coupling=20
> amongst the
> data lines, and significant capacitive coupling as well. =20
> Consequently, the
> characteristic impedances of a single data line are quite higher than=20=

> the 80
> pin case, vary with distance from the ground lines, approaching a=20
> maximum
> the furthest away from the ground lines.  Moreover, the coupling makes=20=

> each
> data dependent on the others.  This coupling dramatically increases=20
> ringing
> after an edge due to the large stored energy and low damping factor=20
> (the
> characteristic impedance is high).  That is one reason for the series
> resistors now used in IDE.  Parallel ATA is essentially a series=20
> terminated
> interface.
>
>
> Charles Hill, consultant
>
> -----Original Message-----
> From: si-list-bounce@xxxxxxxxxxxxx
> [mailto:si-list-bounce@xxxxxxxxxxxxx]On Behalf Of John Lin (=AAL=B4=C2=B7=
=D7)
> Sent: Friday, September 13, 2002 11:45 PM
> To: 'SI-List'
> Cc: John Lin (=AAL=B4=C2=B7=D7)
> Subject: [SI-LIST] AC/DC impedance spec for floppy and 40Pin-IDE=20
> cables.
>
>
> Dear all SI gurus,
>
> Are there any AC/DC impedance spec for floppy cable and 40pin-IDE=20
> cable?
> ATAPI-6 spec. doesn't mention ac impedance for 40pin-IDE but 80pin-IDE
> cable. Can somebody tell the reason?
>
>
> Regards,
>
> John Lin
>
> Quanta Computer Inc.,Taiwan, R.O.C.
> Email: John@xxxxxxxxxxxx
> Tel: 886+3+3272345 ext. 5183
>
>
>
>
>
>
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