16 Channel ADC breakout card with serial interface

[engr_joni_ee]

Hi, I am looking for 16 channel 12bit ADC card with serial interface like I2C or SPI for Microcontroller. I have found MCP 3208 but this is 8 channel. Any suggestion for 16 channel ?

 

[KlausST]

Hi,

You get 187 ADConversion results per second.

So if you have just 1 channel you get 187 conversion results per second of this channel
But if you have two (or more) channels then you have to multiplex them.
This means: Convert channel 0, convert channel 1, convert channel 0, convert channel 1 ... and so on.
So still the ADC converts 187 times per second,
but only 83 times channel 0 and 83 times channel 1

If you have 48 channels, then it conversts: ch0, ch1, ch2, ch 3, ch4 ... ch47, ch 0, ch 1, ...
Still the Adc converts 187 times per second,
but ch 0 (and any other channel) is converted just about 3.9 times per second. About 4 times per second.

****
Stop reading here if deep AD details are likely to confuse you.

Indeed the "187" is not the sampling rate here.
This is because we are talking about a "DelSig" = delta sigma ADC.

Tutorial Sigma-Delta ADCs | Maxim Integrated

A detailed tutorial on Sigma-Delta analog-to-digital converters and modulators. Learn more about over-sampling, noise shaping, and decimation filters.

www.maximintegrated.com

A Delta sigma ADC uses oversampling and a digital modulation filter inside.
So indeed here the 187 is the "data rate". The true sampling rate is maybe 128 times higher ( 187 1/s x 128 = 24k samples/s) .. or much more higher. It depends on the internals of the DelSig.

Other ADCs:
* SAR = successive approximation converter ... typically have no oversampling, thus dataRate = samplingRate
* FLASH ADC .. the same: dataRate = samplingRate
* some audio ADCs use internal oversampling, thus the sampling rate is not the data rate.
(nowadays most audio ADCs are DelSig ADCs)

The benefits of an DelSig:
* cheap
* good linearity
* high resolution
* simple anti aliasing filters
Drawbacks:
* slow
* maybe need additional care when multiplexing input (dummy samples until the internal sigma delta modulator has fully adjusted to the new channel)


Klaus

 

[danadakk]

The conversion rate in this part (PSOC) being discussed, the 12 bit SAR looks like :

Background :

https://www.analog.com/media/en/training-seminars/tutorials/MT-021.pdf

With respect to the DelSig the 187 SPS is the "effective" sample rate. The clock running it
looks like :

Particulars for both found in the architecture manual.

Basic DelSig overview :

https://www.analog.com/en/technical-articles/behind-the-sigma-delta-adc-topology.html

Regards, Dana.