Jump to content

aout_ng problem


Recommended Posts

Finally got around to using an aout_ng, and after some power and wiring issues (read:  I'm a bonehead), it's almost working.  Problem is that the outputs are about half the expected values for each of the configuration settings/steps.

 

Based on the previously mentioned issues, it's mostly likely the DAC, isn't it?  This is the first time I've done anything board level with surface mount, so I'm a bit hesitant...

 

Link to comment
Share on other sites

Thanks for the replies.  Just swapped the out the op-amps and the behavior is the same.

 

What should the DAC output at max?  I really didn't look close, but I think it maxed out at 2/2.5.  Figured the gain should be around 2 and that the amps are working before and after the swap.

 

Not really looking to do bipolar, but the parts are there.  I'll take a look later.

Link to comment
Share on other sites

Just now, cannotthinkofone said:

What should the DAC output at max?  I really didn't look close, but I think it maxed out at 2/2.5.  Figured the gain should be around 2 and that the amps are working before and after the swap.

4.6V at 5V supply (Typical Vdd-0.4)

Best

zam

Link to comment
Share on other sites

Sorry, real life got in the way...

 

So, did some more probing, and found a data sheet.  Data sheet says max output should be AVdd -0.4V.  I don't have my head wrapped around the DAC, but also mentions the Vref out should be around 1V or 2V depending on the mode.  Mines sitting at 1.08.  Running through each channel at max level, I'm getting between 0V and 2.04V. 

 

Looks like I killed the DAC.  Now to figure out how to get it out of there and put a replacement in it's place.

 

Link to comment
Share on other sites

On 15/3/2016 at 8:24 PM, latigid on said:

2.048 is correct.

After the op amps you should get to 10.67V max. Check also your power supply to these. Maybe post a photo of your setup/soldering too.

Hi

No, I check with my DDM finally... i have 4V+ at the DAC output (not Vdd-0.4 as I use a map with high value limit) , the output is 2Vref x (code/0x100)

12 hours ago, cannotthinkofone said:

Sorry, real life got in the way...

 

So, did some more probing, and found a data sheet.  Data sheet says max output should be AVdd -0.4V.  I don't have my head wrapped around the DAC, but also mentions the Vref out should be around 1V or 2V depending on the mode.  Mines sitting at 1.08.  Running through each channel at max level, I'm getting between 0V and 2.04V. 

 

Looks like I killed the DAC.  Now to figure out how to get it out of there and put a replacement in it's place.

 

Yes definitely a problem, you should have the high Vref mode, maybe it's just a start up problem, when some bite define the Vref mode.

Check your serial connection, HW chip line selection, also maybe NG configuration to be sure about soft side chip line selection and correct DAC choices

Best

Zam

 

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

Loading...
×
×
  • Create New...