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Which DAC to choose for my design?

Jake Housley
Intellectual 260 points
Other Parts Discussed in Thread: DAC8812, DAC8162T, DAC8562T

Hello,

I am designing an audiometer and I am using a tone interrupter to create beeps in the tone. In order to do that I am using the THAT2181. It requires a DAC to control the attenuation/gain of the audio signal. The following are the requirements I need the DAC to have:

  • output voltage from 0 to 5V, the higher the resolution the better (at least 12-bit, 16 or more if possible).
  • Very high precision
  • Simple circuit implementation (not too many external components for operation)
  • EMI immunity if possible
  • SPI or I2C interface
  • check the desing reccomendatio below

Thank you

  • 0
    TI__Genius 10615 points

    Hi Jake,

    For this signal attenuation we use a DAC architecture called "Multiplying DACs". A great example would be the DAC8812. This DAC is a 16-bit dual channel MDAC, and it features separate reference inputs so you can attenuate two separate signals of desired. This DAC requires a few external components, you check out this TI Design for help with the design. This particular design does not emphasize the feature of using the reference as a sinusoidal, but the design should still be up to the task, since it is so flexible.

    I have a question in order to be able to provide more insight into the best design type, what is the amplitude and DC bias of the input reference signal? This will determine the number of components needed for this build.

  • 0 in reply to Eugenio Mejia
    Intellectual 260 points

    I'm not using the DAC to attenuate the signal. I'm using the DAC to control the voltage to a chip that will attenuate the signal more precise than any DAC could. Are there any DACs that are preferred for precise voltage control, are immune to EMI, and have less external component complexity? See below for why the DAC is not a good enough to be a signal attenuator for my needs:

  • 0 in reply to Jake Housley
    Intellectual 260 points

    I found the DAC8162T looks like it will work. It has good temperature control and is cost effective and accurate.

  • 0 in reply to Jake Housley
    TI__Genius 10615 points
    Hi Jake,

    I seem to have missed your previous post. The DAC8162T would be a great choice for this application. However I noticed that you wanted a higher resolution. The DAC8162T is a 14-bit DAC, you can take a look at the DAC8562T for a 16-bit option if you are interested. They are both from the same family of devices, it just has increased resolution.
  • 0 in reply to Eugenio Mejia
    Intellectual 260 points
    Hi, thank you for the suggestion. I have one more question: What is the functionality of pin 10 Vrefin/refout? I want my output to be from 0-5V so should I just connect this pin to 5V? Can I leave the pin disconnected? Please let me know any details. Thank you
  • 0 in reply to Jake Housley
    TI__Genius 10615 points
    Hi Jake,

    The DAC8562T has an internal reference of 2.5 V. It is disabled by default. To use it, you must enable it through SPI. The device also has a gain register, and it is set to a gain of 2 when the internal reference is enabled. This means that you can get your 0-5 V output by simply enabling the reference. When you enable the reference the pin has a 2.5 V potential. If you are not using or monitoring this voltage you can leave the pin disconnected, but the the best performance it is recommended to add a 22 nF bypass cap.

    Alternatively you can leave the reference disabled and provide an external 5 V reference voltage. Keep in mind that this reference voltage must be very precise to obtain the resolution that you need from the device.

    You can get more information on page 34 of the DAC8562T datasheet.