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AD7190 doesn't always sample in single conversion mode

Question asked by Ralpok on Jul 24, 2012
Latest reply on Jul 27, 2012 by MaryMc

I have setup my AD7190 to read a signal on Ain 3 - Ain4 in single conversion mode at 4.8khz using the following config:

 

ModeReg:  0x080801

ConfigReg:  0x218

 

After I am done setting up the ADC I am able to read both the Mode and Config registers and have been able to ensure that what I am reading is the same as what I wrote so I have very high confidence that the chip is getting configured as I expect it to be.  Once I get into the mainline of my source I attempt to do a single conversion read of the ADC by doing the following:

 

Drop CS Low

Check /Rdy pin to see if ADC is ready (wait up to 60 us)

     If it is ready then send the read command for the reg I want to read and then clock in data

     If it is not ready I return

 


I am sampling the ADC at 500 hz which is much slower than the max rate it was configured for (4800/4 = 1200 hz).  If I understand how the single conversion mode correctly I would never expect the ADC to tell me it isn't ready when I am sampling at this rate but it often times does.  From the scope traces I have taken it is ~ every 1/5 - 1/10 samples that it never returns as available.  Why is the ADC telling me it isn't ready in single conversion mode?

 

 

Thanks,

Chris

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