Selecction of Analog MUX for a 16bit DAS

[jebaspaul]

Hi,

I am designing a DAS system which needs a board level precision of 14 bits. So, I have decided that it is better to go with 16bit precision in component level.
Input signal frequency : 200Hz (max)
Archtecture : Differential

I need some suggestions from the experience.

For argument we consider an analog MUX from Analog Devices, ADG1207.

There are several parameters to be considered. I start the discussion with OFFisolation.

OFF isolation


In the above curve, OFFisolation Vs Frequency, at lower frequencies there is a flatness. Can any body tell me Why it is flat at lower frequencies. I have gone through so many MUX datasheets. In all datasheets the lower frequency OFFisolation is around -90db.
Since, I am intented for 16bit precision I need atleast -96dB of attenuation at my maximum input frequency (200Hz). Is there any analog MUX available in the market which supports 16 bit precision interms of OFFisolation. Is that interpretation is correct.


Thanks,
Jebas.

 

[crutschow]

The isolation is mainly determined by the stray capacitance between channels, thus it flattens at low frequencies. Since crosstalk is also circuit dependent, depending upon the load impedances, you may have to do a measurement to determine if the device has sufficient crosstalk isolation in your particular configuration.