[SI-LIST] Re: Single crystal driving two different inputs of a chip

Bad idea.

What you should do is use one oscillator to generate a reference that you 
then distribute.

Steve.
At 03:10 PM 6/28/2005 -0700, Rohan Hubli wrote:
>Sorry for the confusion what i meant is  connecting a single crystal =
>resonator to two
>oscillators within a chip
>
>Hope that clarifies my question=20
>
>-----Original Message-----
>From: Joseph Wang [mailto:JYWANG@xxxxxxxxxx]
>Sent: Tuesday, June 28, 2005 3:02 PM
>To: Rohan Hubli; ray.anderson@xxxxxxxxxx
>Cc: si-list@xxxxxxxxxxxxx
>Subject: RE: [SI-LIST] Re: Single crystal driving two different inputs
>of a chip=20
>
>
>Should not be a problem.  In my previous board design, we connect four
>clock inputs together to a signal oscillator, running 33MHz.
>
>Well, you have to know what you are doing.  In rare case, the oscillator
>has very weaker drive strength.  The clock inputs pins on the chip
>should be close enough, not to rise up SI issue, etc.
>
>Anyway, the concern about the jitter is too pessimistic to me.  Any
>reason why and failing case?
>
>Regards,
>Joseph Wang
>
>
>-----Original Message-----
>From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx]
>On Behalf Of Rohan Hubli
>Sent: Tuesday, June 28, 2005 2:46 PM
>To: ray.anderson@xxxxxxxxxx
>Cc: si-list@xxxxxxxxxxxxx
>Subject: [SI-LIST] Re: Single crystal driving two different inputs of a
>chip=20
>
>I am talking about onnecting a single quartz
>oscillator to two clock inputs
>
>-----Original Message-----
>From: Ray Anderson [mailto:ray.anderson@xxxxxxxxxx]
>Sent: Tuesday, June 28, 2005 2:42 PM
>To: si-list@xxxxxxxxxxxxx
>Cc: Ray Anderson
>Subject: [SI-LIST] Re: Single crystal driving two different inputs of a
>chip=3D20
>
>
>Are you asking about connecting a single crystal resonator to two
>oscillators within a chip (I hope not...) or connecting a single quartz
>oscillator to two clock inputs?
>
>-Ray
>
>
>-----Original Message-----
>From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx]
>On Behalf Of Rohan Hubli
>Sent: Tuesday, June 28, 2005 2:38 PM
>To: si-list@xxxxxxxxxxxxx
>Subject: [SI-LIST] Single crystal driving two different inputs of a chip
>
>
>Folks,=3D3D3D20
>
>Can a single crystal be driving two different inputs of a chip that feed
>=3D3D3D
>into=3D3D3D20
>two sensitive analog blocks within a chip. Has anyone had any experience
>=3D3D3D
>
>doing this kind of a thing on the board ?=3D3D3D20
>
>We are facing an issue where a 27Mhz crystal clock needs to be hooked up
>=3D3D3D
>to drive=3D3D3D20
>two sensitive analog cores.=3D3D3D20
>
>If we make the connection internal to the chip then the jitter due to =
>=3D
>=3D3D
>=3D3D3D
>(trace delay + buffer delay + process variations)=3D3D3D20
>has significant impact on the audio quality.
>
>Not to mention the fact that any issues that surface and subsequent =3D
>=3D3D3D
>fixes with this approach will have significant=3D3D3D20
>respin costs for the chip.=3D3D3D20
>
>Your inputs would be greatly appreciated.=3D3D3D20
>
>Thanks
>Rohan=3D3D3D20
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