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Digital Gain in AD9106 does not seem to have an effect. 

Question asked by gtsasha on Jun 7, 2017
Latest reply on Jun 9, 2017 by larrywelchusa

Hello!

 

I am  trying to generate constant output from AD9106 DAC2 and it looks like setting digital gain and DC offset does not have an effect.  

 

I have the following configuration:

 

WAV2_1CONFIG (0x27) is set to 0x0101 to select prestored wavefor constant value

DAC2_CST (0x30) is 0x4000

 

No matter what I set DAC2_DGAIN (0x34) and DAC2DOF (0x24) to there is no effect on the output.  Changing DAC2_CONST (0x30) does change output.

 

What could be the issue?

 

I saw this errata:  AD9106 Errata  but it did not help.  

 

Also, how does AD9106 handle overflow?  What if I DAC2_CONST is set to 3000 (0xbb8) and DAC2_DGAIN to 2.0?  6000 is not representable in 12 bits so what will happen?  Will the signal saturate to 0x0fff (4095) or roll to 0x770 (1904)?  The spec sheet is not clear.  Same for adding DC offset.  

 

Thank you very much!

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