S sparse
S
G reflection for L2/L4
S
V
V
S
G reflection for L7/L9
S
S sparse
With respect to the power decoupling and buried capacitance, I think this
is better done by adding two GND layers if the design can possibly afford it :
S
S
G
S
V
G
G
V
S
G
S
S
I am also a disciple of using plane cuts only with the greatest
consideration. It is fundamental that where the digital logic interfaces
to the RF that none of the digital signals cross a plane cut.
I also agree with that consideration must be paid to which if either
voltage plane is powering the RF, and whether it also powers logic. Once
that is known, then a reasonable stack-up and placement rules can be
generated. Without it, I think we are all firing arrows in the dark.
Regards,
Steve.
At 04:35 PM 8/11/1999 -0500, you wrote:
>Depends on what you are looking for, but the most likely effect is the
>possibility of noise coupling directly between the two power planes. With
>the stackup as shown here, 5V couples tightly to L6 and more loosely to L2,
>giving enhanced plane-to-plane capacitance. If 2.5V needs to be the less
>noisy, then switch L9 and L5 layers.
>
>Ron
>
>
>
>
>Shayle Hirschman <[email protected]> on 08/11/99 07:19:24 AM
>
>Please respond to [email protected]
>
>To: [email protected]
>cc: (bcc: Ron F Parson)
>
>Subject: Re: [SI-LIST] : RF & Digital
>
>
>
>
>An excellent suggestion, Mitch.
>
>Any benefit to switching L6 with L9?
>
>Shayle
>
>
>
>
>At 07:59 AM 8/11/99 -0700, you wrote:
>>Hi Lum,
>>
>>As Shayle states this is a rather odd stackup, and I would certainly not
>recommend it unless I was under duress to comply. This will not get you the
>impedance control you're after unless you take some severe steps to control
>it
>>layer by layer (i.e. differential pairings). I'd suggest the following
>stackup design:
>>
>>L1 : signal
>>L2 : GND
>>L3: signal
>>L4: signal
>>L5: +5V
>>L6: GND
>>L7: signal
>>L8: signal
>>L9: +2.5V
>>L10 : signal
>>
>>Good luck,
>>
>>Mitch Morey
>>Sr PCB Designer
>>San Diego, CA, USA
>>
>>Shayle Hirschman wrote:
>>
>>> Why a stack-up of 4 signal layers in a row (L4 to L7)?
>>>
>>> This seems a bit unusual.
>>>
>>> Shayle
>>>
>>> At 08:09 AM 8/11/99 +0800, you wrote:
>>> >If I have a design that have digital circuit and a small portion of RF.
>>> >There will be some signals going from digital into the RF and out from
>>> >the RF to the digital portion. If the digital portion has to be
>>> >impedance control at 50ohms, how should I go about doing such design to
>>> >ensure that both RF and Digital requirements are taken care of, without
>>> >causing any interference between these two circuits? What about the
>>> >ground? This design will be a 10-layer with the following stack-up :
>>> >L1 : signal
>>> >L2 : GND
>>> >L3 : +5V
>>> >L4 : signal
>>> >L5 : signal
>>> >L6 : signal
>>> >L7 : signal
>>> >L8 : +2.5V
>>> >L9 : GND
>>> >L10 : signal
>>> >
>>> >I would appreciate any advise from you experts out there.
>>> >Thanks and regards.
>>> >
>>> >
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>>> >
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>>
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