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Author Topic: PCB design questions  (Read 1660 times)

PaddleStroke

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PCB design questions
« on: April 23, 2017, 12:29:49 PM »
Hi guys,

I am planning to develop a PCB that will use a H3 SoC and as it is the first time I am trying such a thing I would like to ask few questions in order to get things right.

First thank you very much for the design files, it's a real insight for me as it is the first time I am looking at a SoC PCB. So there is really a lot that I did learn just looking at the files.

For my design, in order to get all the connectors at the right place, I have to make a PCB of 80x140mm. Which is quite big. My questions are on industrialization. Because the PCB is big I fear that the cost will be very high.

- What is an approximate cost of a 6 layers PCB per cm² when producing high quantity (about 1000-5000 pcs)?

- Considering the big size of my PCB, do you think it is possible to make a H3 design on only 4 layers? Do the GND and PWR layers are important for heat sink?

Another possibility would be to make 2 PCB instead of one, one 6-layers 80x70 with the SoC and one 2-layers 80x70 with some of the connectors.

What do you think would be the most cost-effective in industrialization?

Also I read in your blog post that H3 project was cancelled because of heat problem. However I read that with nano version you managed to have less problems with heat. You said that the improvements could be implemented into the normal size.
On the github there is only the normal size files. Not the nano-size files. Are those available normal-size files have been updated with the heat improvement? If no what would be your advices to reduce the heating of the SoC?

Thank you very much for your work! Really really awesome to make designs available. I would have struggle for the even most simple things without those files.


PS: I am not sure it is the right forum to post this topic, sorry about that.

Edit: another question: Why do you make some traces zigzag in the brd?
« Last Edit: April 23, 2017, 12:54:01 PM by PaddleStroke »

PaddleStroke

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Re: PCB design questions
« Reply #1 on: May 05, 2017, 08:35:08 PM »
Hey guys,

For people that would benefit cost estimate for 6 layer PCB (for about 3k pcs) :
80x140 about 2.6$
80x90 about 1.6$
80x60 about 1.1$

I have a design question on the powersupply circuits. On the H3 schematic there is several buck converters, I guess that there is several because they don't have the same voltage and enable.
But I don't understand why they are all different models? Why not using only one model so it will be less different parts?

For example in the H3-Olinuxino schematic there is :
SY8009A -> 1.5V DRAM
LC1463 -> 3.3VA
LC1463 -> 3.3V / VCC-RTC
SY8089A -> 1.2V Sys
SY8113A -> 1.3V CPU

On the orange-pi-zero schematic they use :
SY8008B -> 1.5V DRAM
SY8008B -> 3.3VA / RTC
SY8008B -> 3.3V
SY8089A -> 1.2V Sys
SY8113B -> 1.3V CPU

On the orange-pi-one schematic they don't use the same :
SY8008B -> 1.5V DRAM
RT9050-33GB -> 3.3VA
AMS1117T33 -> 3.3V
SY8089A -> 1.2V Sys
SY8106A -> 1.3V CPU
uP0107BMA5-00 -> VCC-RTC

What I don't understand is that looking at the datasheets they all look much the same. Therefor why not using only one model of SY8009 for example?
Is it because of efficiency of different models better match with required current need?

For SY8113 for CPU, the CPU adjust the output voltage by changing the VDD-CPUFB voltage right?

Thank you!

PaddleStroke

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Re: PCB design questions
« Reply #2 on: September 07, 2017, 08:01:07 PM »
Hey guys,
Another question,
I saw that most H2/H3 boards use SY8113 for the CPU power and I was wondering if there was a specific reason for that. I would like to find a replacement for this buck as SY8113 minimum input voltage is 4.5V and I would like to use a 3.7V lithium bat as power source
Can I just use SY8089A that is usually used for the 1.2V System? I'm guessing there's a reason why they don't use the same part for both system and CPU...

Thanks !
Pierre