Using Sigma-Delta Converters

hi_china59

Analog Devices Application Note AN-388: Using Sigma-Delta Converters

Sample Question:

Q: From your explanation it seems that if I apply an ac signal to the
converter I do not have to worry about idle tones?
A: Well, any ac signal generally has a dc component associated with
it, which will have to be represented by the modulator output,
so the explanation above still applies. But if the total dc input
offset (i.e., internal converter offset plus external offsets) in
your system is exactly 0, the tones will be at dc (0 Hz).
There is another source of idle tones in lower-order «3rdorder)
modulators. The order of the modulator (number of
integrations) is a measure of how much quantization-noise shaping
takes place. Second-order modulators can actually exhibit
bit patterns that show up directly in the baseband, even if
voltage-reference modulation is not occurring. This is one of the
reasons why sigma-delta converters from Analog Devices that
are designed for ac applications use higher-order (~3) sigmadelta
modulators.

sssh

thx 4 sharing

herrgeothe

your sharing is appriciated by us all.

jeffej

Analog Devices Application Note AN-388 Using Sigma-Delta Converters