ADC Channel-to-Channel isolation

Anatoliy Kumpan

Other Parts Discussed in Thread: ADS8681

Hello,
Question regarding proper isolation method with following application requirements:
Voltage measurement
20 channels
Solutions for:
+-5 & +-10 V
800 & 1600 Hz sample rate
8 & 16 bit resolution
Reading from Multiple isolated power rails
High density system
EMI EN55022/32 B or better
Reading voltage from high current sensors distributed all over, the sensors are not isolated.
each sensor provides at least one, ac or dc signal, and a return line.
signal cables are a few meters long.
I currently think that channel to channel isolation is required to eliminate ground loops and receive true differential readings which are not cross biased through ground.
What are your opinions?

over 6 years ago

0 Keith Nicholas over 6 years ago

TI__Mastermind 46200 points

Hi Anatoliy,

Channel to channel isolation will provide the best overall performance, but it depends on the common mode voltages. You mention high current sensors, which implies there may be quite a bit of high frequency noise in your system. If this is expected, then channel to channel isolation is probably the best approach.

Take a look at the ADS8681 family. This is a single channel 16b ADC with programmable input ranges supporting +/-5V and +/-10V ranges, as well as others.

There is also a reference design using the ADS8681 that walks through the process of designing an isolated input channel.

16-Bit 1-MSPS Data Acquisition Reference Design, Isolated for High-Voltage Common-Mode Rejection

Regards,
Keith N.
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