Choosing the right cap - Page 2 - diyAudio
Go Back   Home > Forums > Source & Line > Digital Line Level

Digital Line Level DACs, Digital Crossovers, Equalizers, etc.

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 29th February 2012, 06:22 PM   #11
diyAudio Member
 
Join Date: Feb 2012
SoNic_real_one, thank you, a lot!
This is REALLY helpful for my project. I have so much concern about routing, spending hours copying the schematic is frustuating.
  Reply With Quote
Old 29th February 2012, 08:56 PM   #12
diyAudio Member
 
Join Date: Jan 2008
Location: Virginia
You're welcome. I don't see too many polite people on forums anymore
  Reply With Quote
Old 1st March 2012, 02:02 PM   #13
diyAudio Member
 
Join Date: Feb 2012
Hey again,

Maybe I should start another thread, but since it is about the same datasheet I go on here.
I'm now wondering about powering and grounds. Maybe you've seen it coming .

http://www.ti.com/lit/ds/slas194/slas194.pdf
Page 25 and 26, opamps are powered by 5v, and wired to ground. I believe this is a "mistake". Opamps process analog signals, so they have to be wired to AGND. And their positive inputs are biaised to AVdd/2, so they must be powered by AVdd, which is 3.3v, not 5v. Am I right?
This is what TI did page 26 of this application note:
http://www.ti.com.cn/cn/lit/ug/slau057/slau057.pdf

Isolating analog and digital sections now:
I use an arduino mega, so power supply is regulated.The arduino provides me with 5v and 3.3v power supplies. 5v is my digital supply, and 3.3v the analog one.
I think I will only use one ferrite bead, placed between the two grounds. DGND will be directly wired to power supply ground, and will physically be close to it (to prevent high frequencies currents from returning into the analog part). AGND will be isolated by the ferrite bead.
What do you think?

Knowing that what I'm designing is an audio effect. So this is NOT hifi. And it will be my first pcb design with more than 10 components. So I'm not looking for perfection.

Sorry for english mistakes, everyone noticed I'm not a native ;+).

Last edited by nirv4nh4ck; 1st March 2012 at 02:29 PM. Reason: wrong smiley
  Reply With Quote
Old 3rd March 2012, 05:21 PM   #14
diyAudio Member
 
Join Date: Jan 2008
Location: Virginia
AGND is the same as GND. Bias is provided by VCOM (DAC output) or 2.5V (in the ADC input schematic), and is power by 5V. Is not a perfect, but is a easy arrangement.

Last edited by SoNic_real_one; 3rd March 2012 at 05:26 PM.
  Reply With Quote
Old 3rd March 2012, 07:40 PM   #15
diyAudio Member
 
Join Date: Jan 2010
Quote:
Originally Posted by nirv4nh4ck View Post
And their positive inputs are biaised to AVdd/2, so they must be powered by AVdd, which is 3.3v, not 5v. Am I right?
The text says the maximum differential signal is 4V, so the op amps cannot be powered from 3V3. 5V is correct for AVdd, with 2.5V common mode.
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
cap for adding offset before adc - but which cap in signal path?? thesoundlab Parts 3 31st March 2011 03:50 AM
Choosing replacement coupling cap values studeb Analogue Source 3 15th February 2011 11:37 PM
Polar electro with bypass cap to replace nonpolar as coupling cap? at77 Parts 0 12th January 2010 02:05 AM
choosing cap values for aikido jayme Tubes / Valves 2 25th October 2006 02:09 AM
Low-ESR cap -vs- Normal cap with sunbberized. nina Chip Amps 11 11th September 2005 07:20 PM


New To Site? Need Help?

All times are GMT. The time now is 05:40 AM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2