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Difference in AuxDAC1 and AuxDAC2 vout for all Vref

Question asked by bhatnagar.vaibhav81 on Feb 13, 2015
Latest reply on Feb 24, 2015 by bhatnagar.vaibhav81

Hello,

 

I am using KC705 with AD9364 carte de evaluation and Vivado 2013.4 on 64bit windows based PC with current version of noOS driver.

I want to test the vout of auxDAC1 and auxDAC2 for different Vref(0 to 3) as given in the Figure 51. of UG673 (ref. manual aD9364).

Because, I have to generate some precise voltages for Power Amplifier further.

 

when I set to produce different voltages from init parameters in main.c, it produces the nearby values but the problem is both auxdac1 and auxdac2 produces different voltages.

for example if I want to produce 300 mv

auxDAC1 produces 309.3      and auxDAC2 produces 296.9

Which is always the case. I performed a litte test with several ranges which is attached herewith.

 

I check the values using a multimeter on the given test points near the RXA RF port.

I found that the calculation to write the correct value is done in ad9361.c ad9361_auxdac_set, that is inspired from page 5 of UG 672.

Why there is not option to select the reference voltage and only vref 0 and 3 used?

The if condition is not clear to me.

 

the equation is :


                    (  )=0.97×        +(0.000738+9×10−6×(        ×1.6−2))×                    [9:0]×                    − 0.3572×                    +0.05


however I see that because of step factor that is set to 0 on Reg 0x01A(D4) and Reg 0x01B(D4) the other part of equation is zero.

May be this is the one reason that the output voltage is not precised.  But why there is a difference as we are writing the same value on both of the Registers 0x01A to 0x01B auxdac1 and 2 word (9:0);


Please let me knoo if we make the step_factor 1 how this equation should look like in the ad9361.c?

Did you observe the same problem.


Thanks in advance.


Best regards,


Vaibhav






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