Go Back   Home > Forums > >
Home Forums Rules Articles diyAudio Store Blogs Gallery Wiki Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

Digital Source Digital Players and Recorders: CD , SACD , Tape, Memory Card, etc.

R2R ladder ADC ... any links/sources?
R2R ladder ADC ... any links/sources?
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 7th May 2014, 03:32 AM   #1
gentlevoice is offline gentlevoice  Denmark
diyAudio Member
 
Join Date: Oct 2007
Location: Denmark
R2R ladder ADC ... any links/sources?
Default R2R ladder ADC ... any links/sources?

Hi All,

Hmmm ... I'm curious as to whether R2R ladder ADCs exist and also if there are some links/resources as to how they are designed in practice ...

Might one/some of you know of this?

Thanks for any input you may have

Jesper
__________________
"... It is always possible to be friendly ..." HH the Dalai Lama.
  Reply With Quote
Old 7th May 2014, 04:07 AM   #2
abraxalito is offline abraxalito  United Kingdom
diyAudio Member
 
abraxalito's Avatar
 
Join Date: Sep 2007
Location: Hangzhou - Marco Polo's 'most beautiful city'. 700yrs is a long time though...
Hi Jesper - you could start with this brief from Maxim. They're called 'SAR' ADCs btw.

Understanding SAR ADCs: Their Architecture and Comparison with Other ADCs - Tutorial - Maxim
__________________
I know you think you understand what you thought I said but I'm not sure you realize that what you heard is not what I meant - Alan Greenspan
  Reply With Quote
Old 7th May 2014, 04:09 AM   #3
Jaimo is offline Jaimo  Canada
diyAudio Member
 
Join Date: Oct 2005
I've also wondered about this. I spent a great deal of time studying DAC theory when I was in college but never got the chance to test this concept.

Here's a refresher on R2R theory.

Here's a thread you may want to join...
  Reply With Quote
Old 7th May 2014, 04:51 AM   #4
jcx is offline jcx  United States
diyAudio Member
 
Join Date: Feb 2003
Location: ..
there are also C array based "charge balancing/charge redistribution" SAR ADC
Attached Images
File Type: png cADC.PNG (34.0 KB, 309 views)

Last edited by jcx; 7th May 2014 at 04:56 AM.
  Reply With Quote
Old 7th May 2014, 01:22 PM   #5
rfbrw is offline rfbrw
diyAudio Member
 
Join Date: Oct 2001
Location: .
I think this is what you are looking for.
  Reply With Quote
Old 7th May 2014, 04:37 PM   #6
gentlevoice is offline gentlevoice  Denmark
diyAudio Member
 
Join Date: Oct 2007
Location: Denmark
R2R ladder ADC ... any links/sources?
Hi All,

Thanks for your feedback ;-) - I'll look into it ...

@abraxalito:
Quote:
Hi Jesper - you could start with this brief from Maxim. They're called 'SAR' ADCs btw
... I was actually wondering if this was what it was called when an ADC instead of a DAC.

Just thinking ... might one of you know of a practical schematic so that I could take a glance at how such an ADC is actually implemented?

Thanks again :-)

Jesper
__________________
"... It is always possible to be friendly ..." HH the Dalai Lama.
  Reply With Quote
Old 7th May 2014, 11:54 PM   #7
abraxalito is offline abraxalito  United Kingdom
diyAudio Member
 
abraxalito's Avatar
 
Join Date: Sep 2007
Location: Hangzhou - Marco Polo's 'most beautiful city'. 700yrs is a long time though...
Fig1 in the link I posted shows a block diagram. Do you mean you want a transistor level schematic of that? If so I don't hink its going to happen...
__________________
I know you think you understand what you thought I said but I'm not sure you realize that what you heard is not what I meant - Alan Greenspan
  Reply With Quote
Old 8th May 2014, 01:07 AM   #8
georgehifi is offline georgehifi  Australia
diyAudio Member
 
georgehifi's Avatar
 
Join Date: Sep 2003
Location: Manly Australia (Jewel of the Pacific)
Send a message via MSN to georgehifi
I believe Pacific Microsonics HDCD Model One and Model Two were ad /da and used 2r2 dacs to do it, and they do HDCD as well. I know they still get a small fortune for these on the used market.

Cheers George
__________________
Avatar : Production Lightspeed Attenuator
www.lightspeedattenuator.com
  Reply With Quote
Old 8th May 2014, 05:08 AM   #9
gootee is offline gootee  United States
diyAudio Member
 
Join Date: Nov 2006
Location: Indiana
Quote:
Originally Posted by gentlevoice View Post
Hi All,

Thanks for your feedback ;-) - I'll look into it ...

@abraxalito:
... I was actually wondering if this was what it was called when an ADC instead of a DAC.

Just thinking ... might one of you know of a practical schematic so that I could take a glance at how such an ADC is actually implemented?

Thanks again :-)

Jesper
A long time ago, used a 74HCT393 4-bit binary counter's output to make an analog-output staircase waveform generator.

I don't have a good schematic but the description is simple.

First, I placed an opamp near the overall output, to buffer and sum the DAC's outputs, to make the final analog output signal. To form the signal for the (non-inverting) op amp amp's input, I first put a resistor to ground from the op amp's positive input; call it Rin (and configured the op amp's feedback and negative input network etc for the gain I wanted). Then I placed a resistor with value Rdac (given below) between the 8s bit (digital bit 4 of 4) digital output and the top of Rin, and 2 x Rdac from the 4s bit output to the top of Rin, and 4 x Rdac from the 2s bit output to the top of Rin, and 8 x Rdac from the 1s bit output to the top of Rin.

You can see that it forms a weighted voltage-divider summing network, with voltage-divider weightings that are powers of two (or should be).

I believe there is some simple equivalent multistage R-2R resistor network configuration that makes the same thing as my 8R-4R-2R-R (and some Rin) network.

For some reason, I used 50k for Rin and made Rdac 250k. Today, I would probably try to use smaller values.

In my circuit's case, I also put a small resistance (in the 50 to 400 Ohms range, to fine-tune the total resistance value for each bit) between each digital output and its main DAC resistance, and also added a small cap to ground after each small resistance (1000 pF to 2200 pF), to fine-tune the rise-times and edge shapes.

It worked well. It was for a test instrument (stimulating transistor base or gate), not audio, although I ended up running it in the step-rate range from 30 Hz to 22 kHz, and thus the very nice stair-step edges had frequency components much higher than that. (The DAC output op amp amp's output went to a step attenuator, and the attenuator's output went to a selectable inverting amp and then to an Improved Howland Current Pump op amp amplifier, with a small two-transistor push-pull power amplifier (BD-139/140) inside the Howland's feedback loops, which had an overall output that could be configured with a switch (100 Ohms to ground or not) so that it could produce either voltage steps or current steps, with a peak output of +/-15 Volts at +/-1.5 Amps (barely) into 10 Ohms.)
__________________
The electrolytic capacitors ARE the signal path: http://www.fullnet.com/~tomg/zoom3a_33kuF.jpg

Last edited by gootee; 8th May 2014 at 05:29 AM.
  Reply With Quote
Old 8th May 2014, 06:09 AM   #10
gentlevoice is offline gentlevoice  Denmark
diyAudio Member
 
Join Date: Oct 2007
Location: Denmark
R2R ladder ADC ... any links/sources?
@abraxalito:
Quote:
Fig1 in the link I posted shows a block diagram. Do you mean you want a transistor level schematic of that? If so I don't hink its going to happen...
Hi again ... no I don't mean a transistor schematic but maybe if there were a schematic with actual components used, i.e. ICs etc. it could be interesting to see a practical implementation.

@georgehifi: Thanks for the reference ... yet in this case I'm looking to see how it might be done in practice ...

@gootee: Thank you also for outlining your approach. I'll see if I can put it into a schematic for visualizing it one of these days.

Greetings to you ;-)

Jesper
__________________
"... It is always possible to be friendly ..." HH the Dalai Lama.
  Reply With Quote

Reply


R2R ladder ADC ... any links/sources?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

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
how many 16 bit R2R ladder dacs needed to make 24 bit? rhythmsandy Digital Line Level 25 8th August 2014 03:43 PM
Buffers for ADC design with AK5394A and other ADC's ? JensH Equipment & Tools 66 20th December 2013 08:29 AM
Voltage Sources & Current Sources rascal101 Everything Else 3 13th September 2012 01:56 PM
24-bit R2R DAC using miltiple 16/18/20-bit R2R chips Marek Digital Source 21 1st April 2011 10:05 PM
R2R dac JBL Digital Source 0 4th September 2003 01:47 AM


New To Site? Need Help?

All times are GMT. The time now is 09:03 AM.


Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2019 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 14.29%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2019 DragonByte Technologies Ltd.
Copyright ©1999-2019 diyAudio
Wiki