Other Parts Discussed in Thread: ADS1258, PGA281, PGA280, ADS1261EVM, LM27762
I'm trying to find an appropriate ADC for a data logger system I'm working on...
For my application I need a 24-bit ADC that can take a total of 8 single-ended/16 differential inputs. These may be from a variety of sources of varying magnitude, so I also need a configurable PGA. I will be taking readings from sensors like this (among others), whose output can go negative, so I'm also trying to figure out if I need a bi-polar input range or if the differential inputs remove the need for that. The maximum sample rate I'd need on any one input is 20SPS, but I may wish to oversample. I'm okay with losing a few effective bits due to the PGA/sample rate.
I've come across a few potential ADCs (one being the ADS1256), but none which offer 24-bit resolution and a PGA also offer the number of inputs I require. I'm now thinking the possible routes are:
- Use two 4/8 channel ADCs (possibly SPI daisy chained)
- Use a single ADC with 8 channel 2:1 analogue multiplexer
- Use a larger ADC without PGA, and find external PGAs
If I'm honest I'm very rusty on the AFE side of things and it's been a while since I've needed a dedicated ADC, so I need some advice.
- In general, what would be the best approach/architecture here?
- Can I daisy chain the ADS1256 or is it easiest to just use in parallel?
- Do I need a Bi-polar ADC or do the differential inputs remove this need?
- Is there anything else I need to consider for the AFE?