Layout precautions

Hardware questions and issues with the FV-1

Moderator: frank

Post Reply
FUCHSAUDIO
Posts: 11
Joined: Tue Dec 09, 2008 8:50 am
Location: New Jersey
Contact:

Layout precautions

Post by FUCHSAUDIO »

Are there any parts in-particular that needs to absolutely be closely positioned at chip itself ?

I'm considering a daughterboard arrangement for just the FV-1, for possible inclusion in multiple projects which may not be SMD.
Improving guitar tone, one player at a time....
elmood
Posts: 16
Joined: Sun Jun 01, 2008 3:19 pm
Location: Toronto Canada
Contact:

Post by elmood »

You should put the crystal as close as possible to the chip. Also, it is very important that power bypass caps be directly next to power pins to ensure that the chip is stable during operation.

A daughter board sounds like a good idea. If I were you I'd place the bypass caps, input and output filters and DC blocking caps, etc. on the daughter board. And if you're using it in circuits where it's the only 3.3V circuit, maybe put a 3.3V regulator and even the EEPROM there too. Then it would really just be: power and control in, audio in/out. I'm sure with all surface mount devices you could make this board extremely small.

Good luck with your project!
Kilpatrick Audio - www.kilpatrickaudio.com
Sweetalk
Posts: 141
Joined: Thu Oct 15, 2009 5:13 am

Post by Sweetalk »

I'm desinging a double side board for the FV-1 and have a question about the ground plane. Should be on the FV-1 layer or in the other layer?.

This it's going to be in a pedal enclosure, it is better to put the FV-1 in the "components layer" (as in a single sided board) or in the copper traces layer?.
frank
Posts: 1244
Joined: Wed Oct 19, 2005 12:26 pm
Contact:

Post by frank »

It doesn't really matter, you can put the FV-1 on the component layer if that is easier for production. As long as the crystal and caps are right next to the pins it should be OK. A nice ground plane is a good idea, keep any noisy traces away from the audio traces, etc.
Frank Thomson
Experimental Noize
Sweetalk
Posts: 141
Joined: Thu Oct 15, 2009 5:13 am

Post by Sweetalk »

frank wrote:It doesn't really matter, you can put the FV-1 on the component layer if that is easier for production. As long as the crystal and caps are right next to the pins it should be OK. A nice ground plane is a good idea, keep any noisy traces away from the audio traces, etc.
Thanks a lot Frank, you always answer so quickly. I have another question, the Right and Left outputs are internally buffered?, can I short them together?
frank
Posts: 1244
Joined: Wed Oct 19, 2005 12:26 pm
Contact:

Post by frank »

Uh, best on outputs to use a summing amp configuration rather than shorting together. Left and right inputs can be tied together and driven with the same signal but outputs as a general rule shouldn't be tied directly together.
Frank Thomson
Experimental Noize
ZioGuido
Posts: 5
Joined: Mon Dec 17, 2012 4:24 am

Post by ZioGuido »

I re-up this old thread for a few more questions about precautions to take for a commercial project based on the FV-1:
1) are there any recomendations regarding ESD and other interference matters?
2) are the inputs and outputs already buffered for line level signals or do they need external buffers or filters?
frank
Posts: 1244
Joined: Wed Oct 19, 2005 12:26 pm
Contact:

Post by frank »

There are no special requirements on the interface, you just need to make sure the levels are OK and that they can drive the inputs properly.

Normally the in and out can handle line levels OK but I always prefer a buffer as you never really know what someone else did to their in and out drivers.
Frank Thomson
Experimental Noize
ZioGuido
Posts: 5
Joined: Mon Dec 17, 2012 4:24 am

Post by ZioGuido »

Thanks for your reply, Frank.

Do you have any suggestion for a good buffer design? Also, do I need a buffer for a guitar input as well?
frank
Posts: 1244
Joined: Wed Oct 19, 2005 12:26 pm
Contact:

Post by frank »

For the line level buffer they can be as simple as non-inverting op-amp type, nothing special.

For guitar you really do need a buffer because a guitar's signal is so weak. See the schematics for the SKRM boards on the OCT site, the R01 or G01 versions. Not a fancy buffer but will work for guitar.
Frank Thomson
Experimental Noize
peterv
Posts: 17
Joined: Fri Nov 20, 2009 3:43 am
Location: Netherlands
Contact:

Post by peterv »

Could check the way I completed a Guitar effect unit that's capable for the DIYr. www.echotapper.nl look for eTap2hw
gfisys
Posts: 28
Joined: Wed Dec 14, 2011 7:39 pm
Location: Indonesia
Contact:

Post by gfisys »

Frank, let's say I have a microcontroller sharing power lines and ground with FV-1, would you recommend some sort of power line isolation (e.g using ferrite beads) to keep the power fed to FV-1 immune to high frequency noise that might be present in the power line (due to microcontroller)? Or bypass caps next to FV-1 power pins are sufficient?
frank
Posts: 1244
Joined: Wed Oct 19, 2005 12:26 pm
Contact:

Post by frank »

If you can lay it out so you use a star power and ground pattern that can solve lots of problems. Bypass caps are a must, if the micro has a PLL then keep it as far from the FV-1 as possible since it also has a PLL.

I've not had to use ferrite beads in any FV-1 design so far.
Frank Thomson
Experimental Noize
gfisys
Posts: 28
Joined: Wed Dec 14, 2011 7:39 pm
Location: Indonesia
Contact:

Post by gfisys »

I'll try your suggestion, thanks :D
Post Reply