[SI-LIST] Re: Power supply - Component Placement and Power Distribution.
- From: Prashanth Rajappan <prashanth_rajappan@xxxxxxxxxxx>
- To: "ken@xxxxxxxxxxxxxxxx" <ken@xxxxxxxxxxxxxxxx>
- Date: Fri, 31 May 2013 00:14:49 +0800 (SGT)
Hello Ken,
Thank you for the reply.
As of now we have restriction on the Stackup with number of layers.Thats why i
was more concerned about distributing the
power related components so that we can have more control over the splits in
power plane.
Regarding the Planes Also wouldn't it be be better if the Power planes are
shorter than traveling across the card.
Regards
Prasanth
________________________________
From: Ken Wyatt <ken@xxxxxxxxxxxxxxxx>
To: prashanth_rajappan@xxxxxxxxxxx
Cc: "si-list@xxxxxxxxxxxxx" <si-list@xxxxxxxxxxxxx>
Sent: Thursday, 30 May 2013 8:15 PM
Subject: [SI-LIST] Re: Power supply - Component Placement and Power
Distribution.
Hi Prasanth,
Good question on the power supply planning, but first, let's suggest a
different PC board stack-up.
I would avoid a four layer board as you've indicated. A six-layer would be the
minimum, with 8 or 10 layers even better for this application, it allows much
more flexibility in routing critical nets. Also, you want the power and return
planes to be as close as possible - 3 to 4 mils would be ideal, as this will
provide the best HF bypassing.
There are many schools of thought on the ideal stack-up, but considering the
circuitry you plan to use, I would start with either one or two power plane
"sandwiches" spaced 3-4 mils apart and located towards the middle of the
stack-up. Then arrange your signal layers referencing the appropriate return
planes.
Things to avoid:
1. Don't cross gaps in the return plane with high speed nets.
2. Don't change reference planes without adding adjacent vias (if the reference
planes are the same potential) or stitching caps (if the reference planes are
differing potentials).
3. Don't run high speed nets near the edges of your board or near I/O
connectors.
There are many more aspects of PC board design and I'm sure the group members
will add additional advice.
I'll let someone else address the power supply question.
Cheers, Ken
_______________________
Kenneth Wyatt
Wyatt Technical Services LLC
Woodland Park, CO
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On May 30, 2013, at 8:21 AM, Prashanth Rajappan wrote:
> Hi all ,
> We are currently working on Mixed circuit board which has RF(VUHF) and
> Digital (FPGA and PSoC )circuitary .
> The layer stack up is
>
> TOP
> GND
> Signal1
> Signal2
> Plane
> Bottom
>
> We have 3 different power supply requirement for FPGA and related digital
> circuitry and 3 different power supply for the RF tx/rx side Which is
> generated form one main input power.
>
> My doubt is which is the best way to distribute the power in the board.Should
> all the power modules be in one location and the power to be distributed
> through planes from that location or Should I spread the main power supply
> through the planes and keep the derived power supply locally near to the
> required IC.
>
> Looking forward to comments and suggestions.
>
>
> Thank you ,
>
>
> Regards
>
> Prasanth
>
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