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AD7794 occasional spikes

Question asked by PeterT on Jun 13, 2013
Latest reply on Jun 14, 2013 by J.Gealon



I am using an AD7794 in an application where I measure resistances. When acquiring many consecutive samples in continuous  mode I see occasional spikes ( every couple of 10000 samples) in the signal which I attribute to the ADC. Please see the attached plot. The discretization in the plot comes from formating the output to 3 decimal places.


The setup is as follows:


*  for circuit see attachment

*  DIN is tied high between write operation

*  SCLK  is high in the idle state

*  Sample rate 470 Hz

*  continuous  mode

*  external (ratiometric) reference


Any advice on what might cause this effect ?


Thank you and best regards






I seem that the spike were due to a very noisy TTL RS232 converter IC .... after switching it off during ADC the spikes disappeared ...