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

Joseph

Could you tell me how long is the signal trace? In our PCB, there is also a 
simular case that a crystal is driving three load.

Best Regards

Zhangkun
2005.6.29
----- Original Message ----- 
From: "Joseph Wang" <JYWANG@xxxxxxxxxx>
To: <Rohan.Hubli@xxxxxxxxxxxxxxxx>; <ray.anderson@xxxxxxxxxx>
Cc: <si-list@xxxxxxxxxxxxx>
Sent: Wednesday, June 29, 2005 6:02 AM
Subject: [SI-LIST] Re: Single crystal driving two different inputs of a chip


> 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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