Electronics > PCB/EDA/CAD

EDA for simulation/design up to GHz?

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lgbeno:
Np, happy to help.

That's troubling results with the pull ups, something must have went wrong with your test.      In the example scope trace that you attached earlier, was that with 10k?  I would expect 2.2k to then be better.  10/2.2 times better in fact.

Back to the SI conversation, to address your problem description in the case of the USB impedance changing when you altered your stack up, there no silver bullet to prevent that, and SI tool is certainly not going to help there.  You would need a pcb tool where you can set constraints.  The only one that I've used is Cadence Constraint Manager and it is very expensive.  I don't know anything about Altium but seems like it is top notch so I assume it has something like this. 

Basically it is a spreadsheet where you input things like the stack up, target impedance, length, length matching. Number of vias, and on and on.  It's not a SI tool it's a contest rainy manager...  Then it generates DRC's when you break your constraints in the layout.

Still all of that said, I2C and even the GSM modem stuff.  Probably not complex enough to necessitate a tool like that.  Altium might be a solid investment for other reasons though.

sdim:
I know, I will test the board pin to pin to find out what is wrong.
It's true that I do not need special software for I2C or slow USB, but later when I start using USB 3 (250MHz) and GSM (900Mhz to 2.1GHz) I will need it.
I prefer to start working with good software now (slow speed) so I will be ready for the next step (high speed projects) .

Altium offers an evaluation version.

I'll try it and I hope it will do the job.

Thanks!

nctnico:

--- Quote from: ElectroIrradiator on September 10, 2013, 08:46:03 am ---Are there actually any free/hobby cost level field solvers out there, to be used for evaluating GHz level PCB layouts?

I haven't been able to find any, and am speculating it may be due to a very low interest level for this kind of thing for kitchen desktop use...

--- End quote ---
I always use Sonnet Lite (which is free) for simulating microstrip and RF boards. It takes some time to get the hang of it (defining the layers and drawing the metal layers) but in the end it works like a charm.


--- Quote from: free_electron on September 10, 2013, 09:11:31 pm ---usb does not require 'hi-speed' design skills. it's not until you start fidgeting with ddr3 , sata , pci-x and other wizardry that this stuff comes into play.

--- End quote ---
USB2.0 has speeds over 400Mbit so it does require impedance matched traces.

DavidDLC:

--- Quote from: nctnico on September 12, 2013, 08:50:08 pm ---
--- Quote from: ElectroIrradiator on September 10, 2013, 08:46:03 am ---Are there actually any free/hobby cost level field solvers out there, to be used for evaluating GHz level PCB layouts?

I haven't been able to find any, and am speculating it may be due to a very low interest level for this kind of thing for kitchen desktop use...

--- End quote ---
I always use Sonnet Lite (which is free) for simulating microstrip and RF boards. It takes some time to get the hang of it (defining the layers and drawing the metal layers) but in the end it works like a charm.


--- Quote from: free_electron on September 10, 2013, 09:11:31 pm ---usb does not require 'hi-speed' design skills. it's not until you start fidgeting with ddr3 , sata , pci-x and other wizardry that this stuff comes into play.

--- End quote ---
USB2.0 has speeds over 400Mbit so it does require impedance matched traces.

--- End quote ---

Yes USB requires impedance control usually 90 Ohms, one method is to have the signals layer sandwiched between two ground layers and you need to have control over the trace witdth and trace separation. Usually a good PCB vendor will give you the values for width and separation.

ElectroIrradiator:

--- Quote from: nctnico on September 12, 2013, 08:50:08 pm ---I always use Sonnet Lite (which is free) for simulating microstrip and RF boards. It takes some time to get the hang of it (defining the layers and drawing the metal layers) but in the end it works like a charm.

--- End quote ---

That program looks quite promising, appreciate the reference. :-+

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