Resolving to 16 Bits Using a Precision DAC

I’m using a 16-bit DAC in an industrial control application and I’m having a hard time resolving the LSB.  I know I need to reduce the noise floor – what areas of the application should I address that will have the most impact on the DAC output?".

  • Certainly, you will need to look at all the noise sources/components within the Nyquist bandwidth as it’s the rms sum of these which will contribute to your SNR and hence the noise floor.

    First and foremost, you will need to ensure that the noise of your reference, reference buffer, (if not integrated on the DAC) DAC, Output Amplifier and peripheral components (e.g. gain setting resistors) are a fraction of your LSB. You will need to consider both the low frequency 1/f and wideband noise contributions separately. For  1/f, your design target should be one tenth of an LSB - Modern Amplifier, References and Converters ICs specify this component on the datasheet so this should be easy to sum together. High-Frequency noise can be reduced easily with R-C Filters and in-band noise needs to be computed from the individual noise sources of the signal chain components (don’t forget the discrete devices!) – this is usually specified as noise spectral density (nV/rt-Hz) and you should convert this to a peak-to-peak number by multiplying the rms number by 6.6.

    Let me know if you need further help on this. In the meantime, I am going to refer you to some great reading material on this topic by my ADI colleagues.

    http://www.analog.com/library/analogdialogue/archives/44-04/ad5791.html

    http://www.youtube.com/watch?v=ywChrIRIXWQ&feature=related

    http://www.youtube.com/watch?v=-KcODSYXiZA

    -Liam

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