Optimum Decoupling of Digital ICs - diyAudio
Go Back   Home > Forums > Source & Line > Digital Source

Digital Source Digital Players and Recorders: CD , SACD , Tape, Memory Card, 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 1st March 2004, 01:36 AM   #1
Oli is offline Oli  United Kingdom
diyAudio Member
 
Join Date: May 2003
Location: London
Question Optimum Decoupling of Digital ICs

Application: AD1865N-K non-os dac, Kwak Asynchronous Reclocker

I have been reading a number of data sheets recently, but I keep encountering conflicting advice about decoupling ICs. I have a few questions someone might be able to help me with...

Q. Can I bypass VHC logic with a 220u OS-CON in parallel with a 0.1u ceramic? (Are these values appropriate?)

Q. Should I use resistors or inductors in the power supply lines of my VHC logic to further isolate each noise loop? (Which values?)

How does the situation differ with my OP627 Opamps?
__________________
Oli
  Reply With Quote
Old 1st March 2004, 09:35 AM   #2
diyAudio Member
 
Join Date: Dec 2001
Location: Eindhoven
Default Re: Optimum Decoupling of Digital ICs

Quote:
Originally posted by Oli

Q. Can I bypass VHC logic with a 220u OS-CON in parallel with a 0.1u ceramic? (Are these values appropriate?)

Q. Should I use resistors or inductors in the power supply lines of my VHC logic to further isolate each noise loop? (Which values?)

How does the situation differ with my OP627 Opamps?
Hi

These values will work in most cases.

Yes, you should use inductors, or preferably ferrite beads in series with the lines. In addition watch the Q of the whole decoupling network, otherwise it may resonate.

Opamps: I'd suggest seperate supplies, and 10 to 47 ohm in each supply line, and some decent audio grade lytics.

Take care of correct position of decoupling caps. Some more info can be found in an article I wrote while ago

http://httpd.chello.nl/~m.heijligers...decoupling.pdf

enjoy
__________________
Guido Tent
www.Tentlabs.com
  Reply With Quote
Old 1st March 2004, 10:01 AM   #3
Banned
 
Join Date: Dec 2001
Location: Zamboanga, City of Flowers, Mindanao
Send a message via Yahoo to Elso Kwak
Lightbulb Re: Optimum Decoupling of Digital ICs

Quote:
Originally posted by Oli
Application: AD1865N-K non-os dac, Kwak Asynchronous Reclocker

I have been reading a number of data sheets recently, but I keep encountering conflicting advice about decoupling ICs. I have a few questions someone might be able to help me with...

Q. Can I bypass VHC logic with a 220u OS-CON in parallel with a 0.1u ceramic? (Are these values appropriate?)

Q. Should I use resistors or inductors in the power supply lines of my VHC logic to further isolate each noise loop? (Which values?)

How does the situation differ with my OP627 Opamps?
Hi Oli,
You might find all answers here (80 pages!):
http://www.analog.com/UploadedFiles/...520527817b.pdf


  Reply With Quote
Old 1st March 2004, 11:08 AM   #4
Banned
 
Join Date: Dec 2001
Location: Zamboanga, City of Flowers, Mindanao
Send a message via Yahoo to Elso Kwak
Lightbulb Decoupling

Hi Oli, I now realise that part of your questions may be my fault as I forgot to draw in the schematic the decoupling caps on the flip-flop IC's . Each one has 0.1F ceramic cap directly at the powersupply pin (#14).
For me this goes without saying. Also there is a ferrite bead in the powersupply line between the oscillator and the logic IC's.
  Reply With Quote
Old 1st March 2004, 01:35 PM   #5
diyAudio Member
 
Join Date: May 2001
Location: London UK
Default Re: Re: Optimum Decoupling of Digital ICs

Opamps: I'd suggest seperate supplies, and 10 to 47 ohm in each supply line, and some decent audio grade lytics.

------------------------------------------------------------------------------
Guido

I have often wonder why some manufacturers favour this, whereas others seem to favour lowest PS impedance.

Anyone done sonic evaluation of adding RC filters to opamp PS?
  Reply With Quote
Old 1st March 2004, 02:43 PM   #6
diyAudio Member
 
Join Date: May 2002
Location: Plano , TX
Send a message via AIM to jewilson
Oli,

The OSCON types caps are very good also somtime you might need to use a .01uf instead of .1.

Elso Kwak,

That's a great application note, it's very uptodate.
__________________
Jim W.
  Reply With Quote
Old 1st March 2004, 07:02 PM   #7
diyAudio Member
 
Join Date: Dec 2001
Location: Eindhoven
Default Re: Re: Re: Optimum Decoupling of Digital ICs

Quote:
Originally posted by fmak
Opamps: I'd suggest seperate supplies, and 10 to 47 ohm in each supply line, and some decent audio grade lytics.

------------------------------------------------------------------------------
Guido

I have often wonder why some manufacturers favour this, whereas others seem to favour lowest PS impedance.


Hi

I add resistors to dampen the decoupling. This may also be achieved by using lytics with high ESR

It is quite easy to simulate if your decoupling resonates or not

Ciao
__________________
Guido Tent
www.Tentlabs.com
  Reply With Quote
Old 1st March 2004, 07:16 PM   #8
diyAudio Member
 
Join Date: May 2001
Location: London UK
Default Re: Re: Re: Re: Optimum Decoupling of Digital ICs

I add resistors to dampen the decoupling. This may also be achieved by using lytics with high ESR

----------------------------------------------------------------
What does this do to the sound?
  Reply With Quote
Old 1st March 2004, 07:17 PM   #9
Oli is offline Oli  United Kingdom
diyAudio Member
 
Join Date: May 2003
Location: London
Default Thanks... Anyone tried 'Cho-Drops'

Thanks folks!

Indeed a very good technical article Elso. I need to spend some time to digest at 80 pages.

I am currently using the following devices with your asynchronous reclocker:

Cho-Drop

The data sheet claims they are better than ferrites.

Has anyone else had any experience of these?
__________________
Oli
  Reply With Quote
Old 1st March 2004, 07:26 PM   #10
diyAudio Member
 
Join Date: May 2002
Location: Plano , TX
Send a message via AIM to jewilson
Yes ferrites work well but you have to get the one for the correct frequency. So you have to select the right material. There are lots of possiblities with ferrites.
__________________
Jim W.
  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
DAC digital supply decoupling ? Bernhard Digital Source 1 10th December 2007 12:59 PM
Caps for digital decoupling?? imperfectcircle Digital Source 5 28th July 2006 06:39 PM


New To Site? Need Help?

All times are GMT. The time now is 10:33 PM.


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