I need a 24bit ADC. The AD7779 & AD7771 look great, but the Farnell site seems to indicate that these are not for new designs. I also note that the AD7779 evaluation bard is no longer available from Farnell. I want to avoid choosing the wrong ADC, so I have put my requirements below in the hope recommendations could help me narrow down the Analog Devices ADC options. Then I can sift through the data sheets.
24bits of noise free data
Minimum of 4 channels (8 would be good)
The channel reads must be simultaneous. It must not use a multiplexer.
Precision simultaneous reads across all channels is our goal. The chip price is less important.
The read rate can be quite low, 100 Hz or as low as 50 Hz, so a sigma-delta type ADC is expected. We absolutely need simultaneous reads across all channels and all at 24bits of noise free data, or as close as we can get to this precision. If it is also capable of higher read rates that is a bonus. That would mean we can use it for other tasks as well.
We are measuring single voltage points with reference to an overall ground plane. So we are not performing traditional pairs of differential reads.
The AD7779/AD7771 has a Programmable gain amplifier (PGA) per channel. I would want a PGA for each channel.
If we can exceed 24bits of noise free data that would be a huge bonus as long as it’s a simultaneous read across all channels.
Thanks in advance if you can assist.
I would say that the parts that you mentioned AD7779 and AD7771 as well as AD7770 will fit your requirements. These are still recommended for new designs so ADI recommends utilization of these products. You can check stocks with DIGI-KEY or Mouser, these could probably available there.
Thank you for your reply. That is excellent news, as the AD777x chips look excellent. I will drop a note to Farnell UK to let them know these chips are good for new designs.