Hi there,
I am intending to design a PCB for the Blackfin 531/2/3 dsp. I have not
any experience
in PCB design when it comes to such a high performance processor before,
and I
would like some help and advice on it.
It will need to interface with an omnivision camera module.
My concerns are to do with the chip's packaging, and the physical PCB
itself. I would
like to use a double-sided pcb for this, is it ok if there are no
ground/power planes on
the inner layers of the pcb? What package should i use in this case? I
have absolutely
no experience in ball gate arrays and it looks to me LQFP is the only
option; and only
the BF531 comes in this package.
regards,
Rick
Blackfin DSP PCB Design
Started by ●March 28, 2005
Reply by ●March 28, 20052005-03-28
I would not recommend laying out a high speed board without a ground and
power plane. I'm not sure of the Blackfin packaging but if it is BGA it
would be very difficult to get all the traces out on a two layer board.
At 10:18 PM 3/27/2005, Rick W. Chen wrote:
>Hi there,
>
>I am intending to design a PCB for the Blackfin 531/2/3 dsp. I have not
>any experience
>in PCB design when it comes to such a high performance processor before,
>and I
>would like some help and advice on it.
>
>It will need to interface with an omnivision camera module.
>
>My concerns are to do with the chip's packaging, and the physical PCB
>itself. I would
>like to use a double-sided pcb for this, is it ok if there are no
>ground/power planes on
>the inner layers of the pcb? What package should i use in this case? I
>have absolutely
>no experience in ball gate arrays and it looks to me LQFP is the only
>option; and only
>the BF531 comes in this package.
>
>regards,
>Rick
Steve Holle
Link Communications, Inc.
1035 Cerise Rd.
Billings, MT 59101
sholle@shol...
power plane. I'm not sure of the Blackfin packaging but if it is BGA it
would be very difficult to get all the traces out on a two layer board.
At 10:18 PM 3/27/2005, Rick W. Chen wrote:
>Hi there,
>
>I am intending to design a PCB for the Blackfin 531/2/3 dsp. I have not
>any experience
>in PCB design when it comes to such a high performance processor before,
>and I
>would like some help and advice on it.
>
>It will need to interface with an omnivision camera module.
>
>My concerns are to do with the chip's packaging, and the physical PCB
>itself. I would
>like to use a double-sided pcb for this, is it ok if there are no
>ground/power planes on
>the inner layers of the pcb? What package should i use in this case? I
>have absolutely
>no experience in ball gate arrays and it looks to me LQFP is the only
>option; and only
>the BF531 comes in this package.
>
>regards,
>Rick
Steve Holle
Link Communications, Inc.
1035 Cerise Rd.
Billings, MT 59101
sholle@shol...
Reply by ●March 28, 20052005-03-28
At 11:18 PM 3/27/2005, you wrote:
>Hi there,
>
>I am intending to design a PCB for the Blackfin 531/2/3 dsp. I have not
>any experience
>in PCB design when it comes to such a high performance processor before,
>and I
>would like some help and advice on it.
>
>It will need to interface with an omnivision camera module.
>
>My concerns are to do with the chip's packaging, and the physical PCB
>itself. I would
>like to use a double-sided pcb for this, is it ok if there are no
>ground/power planes on
>the inner layers of the pcb?
NO! Use a serial flash and you can probably get by with 4 layers. I usually
pour the core supply on a layer under the IC as well.
If you use a BGA (needed for the fastest parts) you might need six layers
and 5 mil traces. The QFP is much easier to work with. >What package should i use in this case? I
>have absolutely
>no experience in ball gate arrays and it looks to me LQFP is the only
>option; and only
>the BF531 comes in this package.
BGAs have different layout issues and certainly assembly issues. You can
hand solder QFP boards, you need a contract mfr (CM) for BGAs.
The manufacturers don't package their parts in BGA just to appease the guys
who need small size. They are not trying to make your life miserable
either. As parts become faster, lead inductance of QFPs is an issue. This
goes back to your 2 layer question. You need low impedance power and ground
and don't skimp on the decoupling capacitors.
We deal with these same issues routinely with the SHARC. In this case,
power dissipation also comes into play.
If you do go with BGAs, you want to check with the CM on whether you should
use lead free or leaded BGAs. This is generally not a big deal with other
parts, but since the solder is the ball, it matters a great deal with with
BGAs. It takes a much higher temperature to reflow the lead free BGAs. In
all cases, tell your CM what type of BGA you are using. Al Clark
Danville Signal Processing, Inc.
--------------------------------
Purveyors of Fine DSP Hardware and other Cool Stuff
Available at http://www.danvillesignal.com
Al Clark
Danville Signal Processing, Inc.
--------------------------------
Purveyors of Fine DSP Hardware and other Cool Stuff
Available at http://www.danvillesignal.com
>Hi there,
>
>I am intending to design a PCB for the Blackfin 531/2/3 dsp. I have not
>any experience
>in PCB design when it comes to such a high performance processor before,
>and I
>would like some help and advice on it.
>
>It will need to interface with an omnivision camera module.
>
>My concerns are to do with the chip's packaging, and the physical PCB
>itself. I would
>like to use a double-sided pcb for this, is it ok if there are no
>ground/power planes on
>the inner layers of the pcb?
NO! Use a serial flash and you can probably get by with 4 layers. I usually
pour the core supply on a layer under the IC as well.
If you use a BGA (needed for the fastest parts) you might need six layers
and 5 mil traces. The QFP is much easier to work with. >What package should i use in this case? I
>have absolutely
>no experience in ball gate arrays and it looks to me LQFP is the only
>option; and only
>the BF531 comes in this package.
BGAs have different layout issues and certainly assembly issues. You can
hand solder QFP boards, you need a contract mfr (CM) for BGAs.
The manufacturers don't package their parts in BGA just to appease the guys
who need small size. They are not trying to make your life miserable
either. As parts become faster, lead inductance of QFPs is an issue. This
goes back to your 2 layer question. You need low impedance power and ground
and don't skimp on the decoupling capacitors.
We deal with these same issues routinely with the SHARC. In this case,
power dissipation also comes into play.
If you do go with BGAs, you want to check with the CM on whether you should
use lead free or leaded BGAs. This is generally not a big deal with other
parts, but since the solder is the ball, it matters a great deal with with
BGAs. It takes a much higher temperature to reflow the lead free BGAs. In
all cases, tell your CM what type of BGA you are using. Al Clark
Danville Signal Processing, Inc.
--------------------------------
Purveyors of Fine DSP Hardware and other Cool Stuff
Available at http://www.danvillesignal.com
Al Clark
Danville Signal Processing, Inc.
--------------------------------
Purveyors of Fine DSP Hardware and other Cool Stuff
Available at http://www.danvillesignal.com
Reply by ●March 28, 20052005-03-28
----- Original Message -----
From: "Rick W. Chen" <stuffcorpse@stuf...>
To: <ADSP@ADSP...>
Sent: Monday, March 28, 2005 6:18 AM
Subject: [adsp] Blackfin DSP PCB Design > Hi there,
>
> I am intending to design a PCB for the Blackfin 531/2/3 dsp. I have not
> any experience
> in PCB design when it comes to such a high performance processor before,
> and I
> would like some help and advice on it.
>
> It will need to interface with an omnivision camera module.
>
> My concerns are to do with the chip's packaging, and the physical PCB
> itself. I would
> like to use a double-sided pcb for this, is it ok if there are no
> ground/power planes on
> the inner layers of the pcb? What package should i use in this case? I
> have absolutely
> no experience in ball gate arrays and it looks to me LQFP is the only
> option; and only
> the BF531 comes in this package.
I wouldn't use any less than four layers with ground and power planes, if
the outputs are lightly loaded. Six layers would be better, as the chip has
two supplies. You will probably need to go to eight layers for a BGA
package, to get the tracks to the balls.
Leon
From: "Rick W. Chen" <stuffcorpse@stuf...>
To: <ADSP@ADSP...>
Sent: Monday, March 28, 2005 6:18 AM
Subject: [adsp] Blackfin DSP PCB Design > Hi there,
>
> I am intending to design a PCB for the Blackfin 531/2/3 dsp. I have not
> any experience
> in PCB design when it comes to such a high performance processor before,
> and I
> would like some help and advice on it.
>
> It will need to interface with an omnivision camera module.
>
> My concerns are to do with the chip's packaging, and the physical PCB
> itself. I would
> like to use a double-sided pcb for this, is it ok if there are no
> ground/power planes on
> the inner layers of the pcb? What package should i use in this case? I
> have absolutely
> no experience in ball gate arrays and it looks to me LQFP is the only
> option; and only
> the BF531 comes in this package.
I wouldn't use any less than four layers with ground and power planes, if
the outputs are lightly loaded. Six layers would be better, as the chip has
two supplies. You will probably need to go to eight layers for a BGA
package, to get the tracks to the balls.
Leon
Reply by ●March 29, 20052005-03-29
Hi and thanks for the responses.
Cost is probably the most important aspect for me. The physical dimensions of the pcb is not too much of an issue. Also I expect that I will not need to drive the dsp as fast as it can. Before, I mentioned it needs to process some images from a camera. Well now it seems that it will need to do that for 2 separate video streams from 2 cameras. The images will just be qvga and B&W is sufficient. Perhaps something less than a blackfin is more suitable for this? My application is similar to the one that can be found in http://www.analog.com/library/analogDialogue/archives/38-03/auto_safety.html except it needs to do 2 of it at the same time.
So the way i see it, a QFP package and 4 layers is probably the way to go. I'm waiting for my CM to tell me what they can do with this. cheers
Rick Al Clark wrote:
Cost is probably the most important aspect for me. The physical dimensions of the pcb is not too much of an issue. Also I expect that I will not need to drive the dsp as fast as it can. Before, I mentioned it needs to process some images from a camera. Well now it seems that it will need to do that for 2 separate video streams from 2 cameras. The images will just be qvga and B&W is sufficient. Perhaps something less than a blackfin is more suitable for this? My application is similar to the one that can be found in http://www.analog.com/library/analogDialogue/archives/38-03/auto_safety.html except it needs to do 2 of it at the same time.
So the way i see it, a QFP package and 4 layers is probably the way to go. I'm waiting for my CM to tell me what they can do with this. cheers
Rick Al Clark wrote:
At 11:18 PM 3/27/2005, you wrote:Hi there, I am intending to design a PCB for the Blackfin 531/2/3 dsp. I have not any experience in PCB design when it comes to such a high performance processor before, and I would like some help and advice on it. It will need to interface with an omnivision camera module. My concerns are to do with the chip's packaging, and the physical PCB itself. I would like to use a double-sided pcb for this, is it ok if there are no ground/power planes on the inner layers of the pcb?NO! Use a serial flash and you can probably get by with 4 layers. I usually pour the core supply on a layer under the IC as well. If you use a BGA (needed for the fastest parts) you might need six layers and 5 mil traces. The QFP is much easier to work with.What package should i use in this case? I have absolutely no experience in ball gate arrays and it looks to me LQFP is the only option; and only the BF531 comes in this package.BGAs have different layout issues and certainly assembly issues. You can hand solder QFP boards, you need a contract mfr (CM) for BGAs. The manufacturers don't package their parts in BGA just to appease the guys who need small size. They are not trying to make your life miserable either. As parts become faster, lead inductance of QFPs is an issue. This goes back to your 2 layer question. You need low impedance power and ground and don't skimp on the decoupling capacitors. We deal with these same issues routinely with the SHARC. In this case, power dissipation also comes into play. If you do go with BGAs, you want to check with the CM on whether you should use lead free or leaded BGAs. This is generally not a big deal with other parts, but since the solder is the ball, it matters a great deal with with BGAs. It takes a much higher temperature to reflow the lead free BGAs. In all cases, tell your CM what type of BGA you are using. Al Clark Danville Signal Processing, Inc. -------------------------------- Purveyors of Fine DSP Hardware and other Cool Stuff Available at http://www.danvillesignal.com Al Clark Danville Signal Processing, Inc. -------------------------------- Purveyors of Fine DSP Hardware and other Cool Stuff Available at http://www.danvillesignal.com <*> To visit your group on the web, go to: http://groups.yahoo.com/group/adsp/ <*> To unsubscribe from this group, send an email to: a...@yahoogroups.com <*> Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms
Reply by ●March 29, 20052005-03-29
At 09:48 PM 3/28/2005, Rick W. Chen wrote:
If board space and speed are not big issues then the BF531 in QFP would seem like a good choice. This is a very good DSP for not a whole lot of money. Use a serial flash for boot and you should be able to do everything in 4 layers.
Al Clark
Danville Signal Processing, Inc.
--------------------------------
Purveyors of Fine DSP Hardware and other Cool Stuff
Available at http://www.danvillesignal.com
If board space and speed are not big issues then the BF531 in QFP would seem like a good choice. This is a very good DSP for not a whole lot of money. Use a serial flash for boot and you should be able to do everything in 4 layers.
Al Clark
Danville Signal Processing, Inc.
--------------------------------
Purveyors of Fine DSP Hardware and other Cool Stuff
Available at http://www.danvillesignal.com
Hi and thanks for the responses.
Cost is probably the most important aspect for me. The physical dimensions of the pcb is not too much of an issue. Also I expect that I will not need to drive the dsp as fast as it can. Before, I mentioned it needs to process some images from a camera. Well now it seems that it will need to do that for 2 separate video streams from 2 cameras. The images will just be qvga and B&W is sufficient. Perhaps something less than a blackfin is more suitable for this? My application is similar to the one that can be found in http://www.analog.com/library/analogDialogue/archives/38-03/auto_safety.html except it needs to do 2 of it at the same time.
So the way i see it, a QFP package and 4 layers is probably the way to go. I'm waiting for my CM to tell me what they can do with this. cheers
Rick Al Clark wrote:
At 11:18 PM 3/27/2005, you wrote:
Hi there, I am intending to design a PCB for the Blackfin 531/2/3 dsp. I have not any experience in PCB design when it comes to such a high performance processor before, and I would like some help and advice on it. It will need to interface with an omnivision camera module. My concerns are to do with the chip's packaging, and the physical PCB itself. I would like to use a double-sided pcb for this, is it ok if there are no ground/power planes on the inner layers of the pcb?
NO! Use a serial flash and you can probably get by with 4 layers. I usually pour the core supply on a layer under the IC as well. If you use a BGA (needed for the fastest parts) you might need six layers and 5 mil traces. The QFP is much easier to work with.
What package should i use in this case? I have absolutely no experience in ball gate arrays and it looks to me LQFP is the only option; and only the BF531 comes in this package.
BGAs have different layout issues and certainly assembly issues. You can hand solder QFP boards, you need a contract mfr (CM) for BGAs. The manufacturers don't package their parts in BGA just to appease the guys who need small size. They are not trying to make your life miserable either. As parts become faster, lead inductance of QFPs is an issue. This goes back to your 2 layer question. You need low impedance power and ground and don't skimp on the decoupling capacitors. We deal with these same issues routinely with the SHARC. In this case, power dissipation also comes into play. If you do go with BGAs, you want to check with the CM on whether you should use lead free or leaded BGAs. This is generally not a big deal with other parts, but since the solder is the ball, it matters a great deal with with BGAs. It takes a much higher temperature to reflow the lead free BGAs. In all cases, tell your CM what type of BGA you are using.
Reply by ●March 29, 20052005-03-29
Hello,
--- Al Clark <aclark@acla...> wrote:
> At 09:48 PM 3/28/2005, Rick W. Chen wrote:
>
> If board space and speed are not big issues then the
> BF531 in QFP would
> seem like a good choice. This is a very good DSP for
> not a whole lot of
> money. Use a serial flash for boot and you should be
> able to do everything
> in 4 layers.
Al, I'd like to have you opinion on this: say the user
wants/needs to add external SDRAM, with it's multiple
parallel lines. Could a 4 layered PCB still be enough?
> Al Clark
> Danville Signal Processing, Inc.
>
---------------->
Purveyors of Fine DSP Hardware and other Cool Stuff
> Available at http://www.danvillesignal.com
Jaime Andr Aranguren Cardona
jaime.aranguren@jaim...
jaime.aranguren@jaim... __________________________________________________
--- Al Clark <aclark@acla...> wrote:
> At 09:48 PM 3/28/2005, Rick W. Chen wrote:
>
> If board space and speed are not big issues then the
> BF531 in QFP would
> seem like a good choice. This is a very good DSP for
> not a whole lot of
> money. Use a serial flash for boot and you should be
> able to do everything
> in 4 layers.
Al, I'd like to have you opinion on this: say the user
wants/needs to add external SDRAM, with it's multiple
parallel lines. Could a 4 layered PCB still be enough?
> Al Clark
> Danville Signal Processing, Inc.
>
---------------->
Purveyors of Fine DSP Hardware and other Cool Stuff
> Available at http://www.danvillesignal.com
Jaime Andr Aranguren Cardona
jaime.aranguren@jaim...
jaime.aranguren@jaim... __________________________________________________
Reply by ●March 29, 20052005-03-29
At 08:43 AM 3/29/2005, you wrote:
>Hello,
>
>--- Al Clark <aclark@acla...> wrote:
> > At 09:48 PM 3/28/2005, Rick W. Chen wrote:
> >
> > If board space and speed are not big issues then the
> > BF531 in QFP would
> > seem like a good choice. This is a very good DSP for
> > not a whole lot of
> > money. Use a serial flash for boot and you should be
> > able to do everything
> > in 4 layers.
>
>Al, I'd like to have you opinion on this: say the user
>wants/needs to add external SDRAM, with it's multiple
>parallel lines. Could a 4 layered PCB still be enough?
Maybe.
I haven't tried routing a Blackfin with SDRAM. I assume you are talking 16
bit wide TSSOP. With SDRAM you can sometimes swap certain lines to make
routing easier. I forget which ones without looking carefully. I do this
all the time with SRAM since all the Data and Address lines are arbitrary.
The other thing to remember is that your schematic and pcb layout are
designed recursively. I constantly modify my schematic as I am laying out a
board to take advantage of gate swapping, resistor network pinouts, etc.
I often pour the power and ground planes instead of using a negative plane
layer in my CAD program. This allows you more flexibility with routing
since you may need a occasional trace. You have to be careful with this
idea however.
Of course, it also depends on how large the pcb is and what else is on the
board. If the SDRAM is the only thing connected to the parallel bus,
routing will be much easier. I haven't used a parallel flash since the
ADSP-21161. Booting is plenty fast from a SPI Flash Device.
I very rarely use an autorouter. I occasionally run the autorouter after
parts placement just to see where it gets in trouble. I estimate that
many/most of my boards would take 2 more layers with an autorouter. The
other things to consider are trace width and spacing. 7/7mil boards and
bigger are very routine. As you move to 5/5 or 6/6 fabrication costs go up.
In some cases more layers might even be cheaper. Really small stuff require
microvias (drilled by laser) are very expensive. I never use buried or
blind vias either. These will significantly increase the board cost as well. Al Clark
Danville Signal Processing, Inc.
--------------------------------
Purveyors of Fine DSP Hardware and other Cool Stuff
Available at http://www.danvillesignal.com
>Hello,
>
>--- Al Clark <aclark@acla...> wrote:
> > At 09:48 PM 3/28/2005, Rick W. Chen wrote:
> >
> > If board space and speed are not big issues then the
> > BF531 in QFP would
> > seem like a good choice. This is a very good DSP for
> > not a whole lot of
> > money. Use a serial flash for boot and you should be
> > able to do everything
> > in 4 layers.
>
>Al, I'd like to have you opinion on this: say the user
>wants/needs to add external SDRAM, with it's multiple
>parallel lines. Could a 4 layered PCB still be enough?
Maybe.
I haven't tried routing a Blackfin with SDRAM. I assume you are talking 16
bit wide TSSOP. With SDRAM you can sometimes swap certain lines to make
routing easier. I forget which ones without looking carefully. I do this
all the time with SRAM since all the Data and Address lines are arbitrary.
The other thing to remember is that your schematic and pcb layout are
designed recursively. I constantly modify my schematic as I am laying out a
board to take advantage of gate swapping, resistor network pinouts, etc.
I often pour the power and ground planes instead of using a negative plane
layer in my CAD program. This allows you more flexibility with routing
since you may need a occasional trace. You have to be careful with this
idea however.
Of course, it also depends on how large the pcb is and what else is on the
board. If the SDRAM is the only thing connected to the parallel bus,
routing will be much easier. I haven't used a parallel flash since the
ADSP-21161. Booting is plenty fast from a SPI Flash Device.
I very rarely use an autorouter. I occasionally run the autorouter after
parts placement just to see where it gets in trouble. I estimate that
many/most of my boards would take 2 more layers with an autorouter. The
other things to consider are trace width and spacing. 7/7mil boards and
bigger are very routine. As you move to 5/5 or 6/6 fabrication costs go up.
In some cases more layers might even be cheaper. Really small stuff require
microvias (drilled by laser) are very expensive. I never use buried or
blind vias either. These will significantly increase the board cost as well. Al Clark
Danville Signal Processing, Inc.
--------------------------------
Purveyors of Fine DSP Hardware and other Cool Stuff
Available at http://www.danvillesignal.com
