AD4030 Output Code

Question

I performed some measurements on the AD4030 evaluation board. 
 The data acquisition was carried out using custom firmware rather than the ACE environment. 
 The initial measurements I conducted involved zeroing both the IN0+ and IN0- inputs by connecting two 50-ohm SMA termination resistors. 
 The output codes of the ADC were all very close to the 8388607 code, with only a very small deviation at the LSBs. 
 When I applied 1 VDC to one input while the second one was connected to the ground (i.e., grounded), the output codes were approximately 0.5 VDC. 
 When I applied 2 VDC to one input and connected the negative input to the ground, the output code produced approximately 1 VDC. 
 Is there any explanation for this functional behavior? 
 With a zero input, shouldn't the output code also be around 0, i.e., either 0x00000 or 0xffffff?

NathanT · Accepted Answer

Hi elsiesemico ,

You could also use ACE software to check whether you will still get the output of 0.5 V if your input voltage is 1 V. Also, you were right about the 0 V input being able to be able to get an output of 0x000000 or 0xFFFFFF; it can also swing to 0x000001. Since the midscale is near to 1 LSB. On the other hand, noise within the system could also be a factor for the swinging of the output.

Let me know if any of these insights will be a help to you. So that I could further assist you.

Regards,
Jo

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AD4030 Output Code