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AD5541/2 AD5541A/2A noise specification

Question asked by splin on Nov 9, 2017
Latest reply on Nov 15, 2017 by musach

I'm looking for a very low noise 16 bit DAC and the AD5541A and AD5542A stand out with a 0.1 - 10Hz noise specification of only 0.134uV p-p. After a  few moments of reflection though, this seems hardly credible given the noise spectral density is specified as 11.8nV/sqrt(Hz), which seems a reasonable value.

 

Even if the DAC exhibits no 1/f noise, this would equate to 11.8 x sqrt(10 - 0.1) = 37nV rms or 245nV p-p in the band .1 to 10Hz.

 

CN-0079 shows a measured noise output plot of 5.7uV p-p for an AD5542, but presumably a fair chunk of this is from the ADR421 reference (1.75uV p-p typical spec) and a little more from the buffer amplifier (0.5uV p-p typical spec).

 

Is the real value known?

 

LF noise doesn't seem to be specified for many R-2R DACs. Is this because they don't suffer much 1/f noise? I can see that the R-2R and/or feedback resistors are likely to be the main noise contributors (ignoring references and buffers) but I would have expected silicon diffused resistors to have some excess (1/f) noise?

 

What would be a good choice for a very low noise, especially LF noise, 16 bit DAC? Stability of linearity with temperature is very important as is cost but speed isn't (a few hundred SPS at max). It doesn't have to be R-2R but support for a 10V reference would be a definite advantage. Bipolar is preferred, but again is not essential. The AD5760 looks good but is a bit pricey.

 

Thanks, Tony H

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