ADAU196XAZ test, i can't get a digital input 24bit signal by the sigmastudio or the ARWB

HI

i bought the board EVAL-ADAU196XAZ, and want to get a pure analog output using this board.

the inportant thing is to generate a 24bit digital input signal, i see other DAC use the sigmastudio to program the board easily to get a input signal.

but in this board EVAL-ADAU196XAZ, when i use the sigmastudio, there is no schematic workspace, so can't add the input.

the ARWB can only control the register of the chip ADAU1966A, this software can't generate a 24bit digital input signal.

my question is how can we get a digital input to the EVAL-ADAU196XAZ, can ypu help provide some software to help generate the digital input?

thanks

Shangzheng

Parents
  • +1
    •  Analog Employees 
    on Feb 27, 2020 3:06 PM

    Hello Shangzheng,

    The SigmaStudio interface is only for controlling and setting the registers. Once all the settings are correct for your application it is easy to copy all the register settings so your system controller can properly program the part. This is the use of SigmaStudio with this part to give you real time control of the part.

    Audio has nothing to do with SigmaStudio. There is no way to get audio in or out. This is true even with a DSP.

    This evaluation board does not have an analog input. All the inputs are digital. The easiest way is to use an S/PDIF signal and send that to the board. There are provisions on the board to route this audio to all the outputs or only to selected outputs.

    The board can also be setup to receive an I2S or a TDM signal from some other digital source. This is often a DSP evaluation board. Do you have any of our DSP evaluation boards?

    I have also attached an updated user guide that is still a preliminary guide. It covers the old revision in the first half of the document and the new revision in the second half of the document.

    Dave T

    PDF

  • Hi Dave

    I am afraid i don't say clearly in the last reply,

    i am not trying to send ab audio signal, i am trying to use sigmastudio to create the code for high resolution sinewave that can be output from the ADAU1966A, the adau1966a is actually supposed to CREATE the audio frequency sinusoid(it is not an audio signal).

    1. i have the impression that i can use either sigmastudio(easiest) or the ARWB program (harder) to creat the digital code of a high quality 16/20/24 bit sinusoid@192/94/48Ksps and directly load this to the DAC via the little daughter card(connected to jumper J4 or whatever that interface to the PC)

    2. i don't want to have to load the digital signal through the external data ports.

    3. after configure well, i still unable to see the ADAU1966 DLL in sigmastudio, means there is no schematic workspace in this one, you can see last reply, so that i can't add the I/O, where are things break down, 

    4. finally, if this method isn't possible, if there is an available source of document to connect the matlab - as an alternative way of creating the digital representation of the sinusoid if it is not possible to do this using sigmastudio, or if this is easier than using the ARWB software.

    at last, if there is a newer version of the sigmastudio user's guide or document tation or an application note that might have an example that's fairly close to what i am trying to accomplish.

    thaks advancd

    Shangzheng

  • 0
    •  Analog Employees 
    on Mar 6, 2020 2:11 PM in reply to 杨尚争

    Hello Shangzheng,

    The output of the DAC is actually riding up on the common mode voltage. The common mode voltage is around 1.5V. You can see this on your scope if you probe the SMT test points that are to the left of the output coupling caps. I circled them in this picture. On these test points you can get the raw output of the DACs that is riding up on the 1.5V common mode DC offset. Keep in mind that this is the raw unfiltered output so there is a lot of out-of-band energy in the signal at this point. 

    The schematic is in the user guide that I attached at the top of this post. 

    Having the common mode at 0.9V will mean that the signal will clip unsymmetrically. Which means it will clip on the bottom of the waveform sooner than the top. This will limit your max level before distortion. So I am not sure why you want it centered around 0.9V unless you are interfacing to a device that is using a 1.8V AVDD. 

    So you may need to do some level translation to match the common mode signal of 0.9V of the target device. 

    I will go into the shop and take a quick measurement of the ADAU1701 output for you. 

    Dave T

  • 0
    •  Analog Employees 
    on Mar 6, 2020 8:49 PM in reply to DaveThib

    Hello Shangzheng,

    I went into the lab and made some measurements. 

    See if this will meet your needs.

    Both of these were done with an internal oscillator set to -1dBFS

    This first one is the EVAL-ADAU1701MINI eval board.

    This one is the EVAL-ADAU1452RevBZ

    They both are pretty good. The ADAU1452 is using one of our popular codecs that was designed after the ADAU1701 was designed. The eval board already has all the connections you need. 

    By the way, going up in sample rate did not improve the distortion components you see. So unless you need to run that high there is no point in it for just producing a sine wave. Perhaps once you get up to 20kHz it would make a difference but at 1kHz it does not. 

    To modify the EVAL-ADAU1452RevBX to operate at higher sample rates will need some decent soldering skills and equipment. The instructions are in the user guide. The EVAL-ADAU1701 would require no modifications to run at higher rates. Just some settings in SigmaStudio.

    Dave T

  • Hi Dave

    Thanks a lot for your advice and help, all of them help a lot.

    i am going to consider about the board eval-adau1701 and eval-adau1452revbx. 

    sincerely

    Shangzheng

  • Hi Dave

    I see from the picture, the SFDR of the EVAL-ADAU1701MINI is 75dB and the EVAL-ADAU1452RevBZ is 85dB, we want to get a better signal like the SFDR higher than 90dB.

    I am afraid the amplifier limit the output analog signal of those two board, the amplifier after the DAC provide the drive ability to the output. i am not quiet sure about this. maybe the signal directly from the DSP is very good, and limit by the board DAC and the amplifier?

    and now, i want to buy one board 1701 or 1452, and i only want to use the DSP on the board,( because the dac on the board is worse than adau1966), and then send the digital signal direct to my board EVAL-ADAU196XAZ, which board is more easy to connect and more easy to program, i want a high quality digital signal from the DSP and then directly to EVAL-ADAU196XAZ, so that i can get a high quality analog output sinewave signal. which board is more suitable to buy? and i only want to use the DSP of the board.

    Thanks 

    Shangzheng

  • Hi Dave

    we decide to buy the board EVAL-ADAU1452REVBX, this dsp is pretty powerful, and can meet our requirement.

    and ths last question is how can i change the common mode output in the EVAL-ADAU196XAZ, because i want to change the common mode level.

    you reply me that change the common mode need some level translation to match the common mode signal, so could you give a more detail description about changing the output common mode voltage of the EVAL-ADAU196XAZ?

    Thanks

    Shangzheng

Reply
  • Hi Dave

    we decide to buy the board EVAL-ADAU1452REVBX, this dsp is pretty powerful, and can meet our requirement.

    and ths last question is how can i change the common mode output in the EVAL-ADAU196XAZ, because i want to change the common mode level.

    you reply me that change the common mode need some level translation to match the common mode signal, so could you give a more detail description about changing the output common mode voltage of the EVAL-ADAU196XAZ?

    Thanks

    Shangzheng

Children
  • 0
    •  Analog Employees 
    on Mar 10, 2020 5:22 PM in reply to 杨尚争

    Hello Shangzheng,

    The internal common mode voltage out of the DAC can be changed but it will change some of the specifications out of the DAC. You are worried about the performance of the other codecs I mentioned having some distortion components that are not below -90dB. If you use a common mode voltage of 0.9V and then amplify this I am fairly certain you will not meet the performance goals you seek. 

    To do this you shut off the internal voltage reference. It is located in the PLL_CLK_CTRL1 register and you set the VREF_EN bit to 0. 

    Then you drive the CM pin with an external Op-Amp setup as a voltage follower with the 0.9V reference of your circuit. Read the Power Supply and Voltage Reference section of the datasheet. Page 20. 

    For the best performance I think you should look at the Typical Application Circuits section of the datasheet. You will need to use one of those filters and they are all capacitor coupled so those circuits will keep the common mode voltage untouched. Then after this filter you need to use another Op-Amp stage that will be referenced to your common mode voltage. This is done with standard amplifier designs. I think this approach will give you the best performance. You can use the evaluation board to breadboard this design. The evaluation board has the simple passive filter that can be bypassed and you can take the output of the DAC directly over to an prototype board of your design to test this. Then you can also test the performance if you shut off the internal voltage reference and drive your CM voltage into the DAC. If performance is that important to your design then prototype both approaches. The evaluation board was built for this purpose. 

    Dave T

  • Hi Dave

    Thank you very much, all of this helps a lot.

    best regards

    Shangzheng

  • Hi Dave

    With your help, i can use EVAL-ADAU1966A to get a good analog signal now, I have some questions about the EVAL-ADAU1966A board, also about the DAC chip adau1966.

    let me tell you about my configuration, for the EVAL-ADAU1966A, i set the adau1966 work at 192ksps mode. and generate a analog output, use differential output of veal-adau1966, also remove the cap c2, c3, remove the res R3, R4. you can see in the below, i do this mainly to get the common mode voltage 1.5v, because we know the adau1966 itself can generate a common mode voltage.

    but after do s measurement, i calculate the noise is big, about rms noise 10mv at the bandwidth of 128k.

    so i find if with this c2, c3, r3, r4, the noise is much better, we know the c3 and r4 is a high pass filter, why this bring so much difference.

    another thing is i try to check the output noise spec in the datasheet  of adau1966, but i didn't find the noise spec, so do you have some idea about the noise spec of eval-adau1966?

    in the adau1966 datasheet, this give the analog audio output resistive load is 3100 ohm per pin.

    my main aim is to use the common mode 1.5v in the eval-adau1966, we know the adau1966 itself can generate a dc common mode voltage.

    Thanks 

    Shangzheng

  • 0
    •  Analog Employees 
    on Apr 17, 2020 10:53 AM in reply to 杨尚争

    Hello Shangzheng,

    You must also remove R6 and install R2 (237 ohms) and change R1 to a 237 ohm resistor. This will make the output be differential instead of single ended and adjusts the filter to be differential. 

    You cannot load down this output very much. So it is recommended to use a high impedance differential input stage and to filter the audio to remove the out of band energy. C1 does some of the job but it can be done better with an active filter. 

    These filters are all detailed in the Typical Application Circuits section of the datasheet. It should be on page 13. The active filter shown in figure 12 works well however, it is still not DC coupled. You will have to make adjustments if you need the DAC to go all the way down to DC. 

    If you are using the low propagation delay (low latency) 192kHz mode of the DAC then there will be a lot of out of band noise. It is the tradeoff for making the filter fast.

    There is a Common Mode voltage pin that you should be using to reference your circuits and you will need to buffer this CM voltage to avoid crosstalk. The CM pin is pin 62. You must have the filter caps on this pin but then you can take that voltage and use a voltage follower to drive external circuits. 

    To answer your question about the noise. I think it might be due to the loading of the external circuits after you removed the caps. 

    Dave T

  • Hi Dave

    Thanks for your help. 

    I bought a amplifier in ADI, which is ADA4945-1CP-EBZ, this amplifier can provide a common mode voltage with good quality.

    sincerely

    Shangzheng