Post Go back to editing

AD9959 channel output signal amplitude and phase

Category: Software
Product Number: AD9959

Greetings !

3 moths ago, I started developing a driver in #C in order to control manually the AD9959 with a microcontroller, so far, I can output different frequency, phase and amplitude from each channel the problem is that the channel don't have the same amplitude and are not in phase. Also, there amplitude seems to change with the frequency I choose. I am convince this is not normal and can't find the maximum amplitude for each channel in the datasheet. Channel 2 and 3 have the same amplitude and  phase but its not the same the output signal from channel 0 and 1. In my first use I set the first 10 bits of the ACR register to 0x3FF which should corresponds to an amplitude scale factor of 1 for each channel but it turns out the amplitude is not the same for all channel. As for the phase, I write 0 as a phase offset word in the CPOW0 register and the signals are not in phase.

I'm resetting the board with the MASTER_RESET pin  before doing all those operations so I have a hard time finding the problem. Do I need to enable the amplitude multiplier enable bit ACR[12]  or should it must be set to 0 if  I want to control the amplitude, for now I set it to 1 every time. I also would like to know the max output amplitude for each channel because for now it seems to change in function of the frequency .

Thank you for your time.

Parents
  • Hi  ,

    Let me take a look at this and see what I can do. I have to consult my colleagues if they have other ways to have these channels in phase. 

    All the best,

    Jules

  • Hi  ,

    Ok waiting for your answer.

    Updates!

    Right now i'm playing with the evaluation software and I see that the signals tends to be more in phases with increased frequency in the order of the 100 KHz, while at 25 KHz i had the same results with the driver I implemented, I am more than confused I was expecting to see all the channel outputs in phase no matter the frequency in the evaluation software. I'm keeping it with my investigation. For more information, here is a screenshots of the output signals both with the evaluation software and with my drivers. I also included the setup I used with the evaluation software, with a clock of 25Mhz since I used an external crystal clock to control the chip manually.

    The Channels output Amplitude and phase difference between channels with the Evaluation Software

         

    The Channels output Amplitude and phase difference between channels with my C driver

        

    As you can see the results are quite similar but I was expecting to have all the channel output in phase in both cases.

    Thanks again

Reply
  • Hi  ,

    Ok waiting for your answer.

    Updates!

    Right now i'm playing with the evaluation software and I see that the signals tends to be more in phases with increased frequency in the order of the 100 KHz, while at 25 KHz i had the same results with the driver I implemented, I am more than confused I was expecting to see all the channel outputs in phase no matter the frequency in the evaluation software. I'm keeping it with my investigation. For more information, here is a screenshots of the output signals both with the evaluation software and with my drivers. I also included the setup I used with the evaluation software, with a clock of 25Mhz since I used an external crystal clock to control the chip manually.

    The Channels output Amplitude and phase difference between channels with the Evaluation Software

         

    The Channels output Amplitude and phase difference between channels with my C driver

        

    As you can see the results are quite similar but I was expecting to have all the channel output in phase in both cases.

    Thanks again

Children
No Data