A
Apparatus
- Jan 1, 1970
- 0
Hello,
** I feel somewhat overwhelmed by my pcb design task, so I appologize
in advance for the length/convoluted-ness of this post. I have
attempted to compact and clarify as best as I can.
I am designing a PCB of an embedded system with mostly SMT parts. The
board includes audio (TI TLV320AIC1106) and ethernet subsections
(Cirrus Logic CS8900A). It also includes an Oki Semiconductor ML67Q5003
ARM microprocessor running at 20MHz (4x PLL) clocked by a 5MHz
oscillator. It draws not more than 0.5A, is only two layers, and has
three regulated voltages (5, 3.3, 2.5)from a 16V 500mA wall-wart
transformer.
Using a trace width calculator at www.33each.com, I find that the 8mil
signal traces on my board are wide enough to route power. Should I make
them thicker (100mil?) anyway? Thicker traces confuse the Altium Situs
auto-router around my SMT components so I would prefer not to unless
needed.
How important are ground/power planes here? Since this is a two layer
board with close to 500 connections on the pcb, even with a 6x8" board,
space is tight around the SMT chips, so I would like to avoid planes if
possible. If I do add a plane, should I include dead/unconnected copper
portions of the plane? Should planes be placed before or after
auto-routing?
What other considerations should I take? What can make routing easier?
I've been playing with Protel DXP for a few days and was finally able
to generate a fully routed board that I think meets manufacturing
specs, but it was a long iterative process getting here.
Does Advanced Circuits (www.33each.com) have standard hole sizes? Is it
safe to exactly meet there minimum requirements for trace/via/pad
separation on much of the board?
Answers or feedback to any of these questions are much appreciated.
Happy Holidays,
Chris
** I feel somewhat overwhelmed by my pcb design task, so I appologize
in advance for the length/convoluted-ness of this post. I have
attempted to compact and clarify as best as I can.
I am designing a PCB of an embedded system with mostly SMT parts. The
board includes audio (TI TLV320AIC1106) and ethernet subsections
(Cirrus Logic CS8900A). It also includes an Oki Semiconductor ML67Q5003
ARM microprocessor running at 20MHz (4x PLL) clocked by a 5MHz
oscillator. It draws not more than 0.5A, is only two layers, and has
three regulated voltages (5, 3.3, 2.5)from a 16V 500mA wall-wart
transformer.
Using a trace width calculator at www.33each.com, I find that the 8mil
signal traces on my board are wide enough to route power. Should I make
them thicker (100mil?) anyway? Thicker traces confuse the Altium Situs
auto-router around my SMT components so I would prefer not to unless
needed.
How important are ground/power planes here? Since this is a two layer
board with close to 500 connections on the pcb, even with a 6x8" board,
space is tight around the SMT chips, so I would like to avoid planes if
possible. If I do add a plane, should I include dead/unconnected copper
portions of the plane? Should planes be placed before or after
auto-routing?
What other considerations should I take? What can make routing easier?
I've been playing with Protel DXP for a few days and was finally able
to generate a fully routed board that I think meets manufacturing
specs, but it was a long iterative process getting here.
Does Advanced Circuits (www.33each.com) have standard hole sizes? Is it
safe to exactly meet there minimum requirements for trace/via/pad
separation on much of the board?
Answers or feedback to any of these questions are much appreciated.
Happy Holidays,
Chris