cannotthinkofone Posted March 15, 2016 Report Share Posted March 15, 2016 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... Quote Link to comment Share on other sites More sharing options...
Zam Posted March 15, 2016 Report Share Posted March 15, 2016 Hi Half voltage at the DAC output or at the buffer output ? Best Zam Quote Link to comment Share on other sites More sharing options...
latigid on Posted March 15, 2016 Report Share Posted March 15, 2016 Are you using the bipolar mode? There's a known issue with equal divider resistors. Quote Link to comment Share on other sites More sharing options...
cannotthinkofone Posted March 15, 2016 Author Report Share Posted March 15, 2016 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. Quote Link to comment Share on other sites More sharing options...
Zam Posted March 15, 2016 Report Share Posted March 15, 2016 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 Quote Link to comment Share on other sites More sharing options...
cannotthinkofone Posted March 15, 2016 Author Report Share Posted March 15, 2016 Yeah, looks like I killed the DAC. I'll double check, but I don't thinks there's more than 2.5V out. That actually helps. thanks. Quote Link to comment Share on other sites More sharing options...
Zam Posted March 15, 2016 Report Share Posted March 15, 2016 I have a doubt, maybe it's 2.048V typical... Quote Link to comment Share on other sites More sharing options...
cannotthinkofone Posted March 15, 2016 Author Report Share Posted March 15, 2016 Then what should gain on the amps be? Quote Link to comment Share on other sites More sharing options...
Zam Posted March 15, 2016 Report Share Posted March 15, 2016 1+(R1/R2) Quote Link to comment Share on other sites More sharing options...
latigid on Posted March 15, 2016 Report Share Posted March 15, 2016 (edited) Just now, Zam said: I have a doubt, maybe it's 2.048V typical... 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. Edited March 15, 2016 by latigid on Quote Link to comment Share on other sites More sharing options...
cannotthinkofone Posted March 18, 2016 Author Report Share Posted March 18, 2016 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. Quote Link to comment Share on other sites More sharing options...
Zam Posted March 18, 2016 Report Share Posted March 18, 2016 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 Quote Link to comment Share on other sites More sharing options...
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