DAC80508: Understanding and Calculating the total noise for a DAC output

Spencer Curbelo

Part Number: DAC80508

Hello,

I am a bit confused about calculating the total noise from the DAC Outputs. Specifically I don't understand this table

(Can be found on page 8 of the datasheet)

I think it is first telling the noise over the bandwidth of 0.1Hz to 10 Hz at 14uV. Then it specifies over larger bandwidths but how can the 10kHz noise bandwidth be lower than the 1kHz bandwidth? Are they meant to be taken together to get a total noise i.e. when the gain is 1 55 nV/sqrt(Hz) should be used from 1 kHz to 10kHz and then 50 from that point on. Also isn't 55 far lower than the graph shown on page 18 of the data sheet.

Any help would be greatly appreciated

over 1 year ago

+1 Katlynne Jones over 1 year ago

TI__Mastermind 42273 points

Hi Spencer,

The noise looks to be ~55nV/sqrt(Hz) in the plot to me at 1k, and 50 at 10k for the gain = 1:

The noise spectral density curve represents the noise contribution from all frequencies of random noise. There is less noise contribution from higher frequency sources on this device which is why the noise value at higher frequencies is lower.

To translate this to an RMS noise or peak to peak noise, you would need to take the integral under the curve based on the bandwidth of the circuit. If you had a filter, the noise contributions from the frequencies filtered out by your filter would not be included in the total noise.

These two noise videos on the op amp precision labs should help explain the concept:

https://www.ti.com/video/series/precision-labs/ti-precision-labs-op-amps.html#transcript-tab

Best,

Katlynne Jones

0 Spencer Curbelo over 1 year ago in reply to Katlynne Jones

Prodigy 20 points

Thanks!

Data converters

Data converters forum

DAC80508: Understanding and Calculating the total noise for a DAC output