I am looking to select a couple of data converters for an instrument I am designing. The company I work for has glacial product development life cycles so whatever I parts I pick need to be supported for the long haul (the previous generation of their products was designed in the '90s). I know that Analog Devices is buying Linear Tech which doesn't give me warm fuzzies about any part in either companies portfolio right at the minute. Don't force me to go to TI for this now.
ADC 1: One channel, 18 bit, high DC precision, 100 to 250 KHz sample rate, differential inputs, and a SPI interface. A SAR is what I am looking for. The SAR we most recently used was the AD7691 and we found it's performance acceptable. However, I really don't want to base a new family of products on a part that might be obsolete in 3 years.
ADC2: One channel, 24 bit, high DC precision, ~10 Hz output rate, differential inputs, and a SPI interface.. This will just about have to be a delta-sigma part.
I am also looking for 16 bit voltage output DAC as well. SPI, +/-10V, 10 uS settling time or better. The AD5761R looks interesting, but again longevity is a key characteristic more so than cost.
Let me know if anybody has any insight into what Analog Devices is planning to do with their and Linear Tech's portfolio of parts.
The AD7691 is part of a 10 pin SAR family that are pin and package compatible. You can see this in the parts table in the AD4003 datasheet (table 8). The most recent release in this 10 pin compatible family is the AD4003 which was released last Nov. So even though there is no risk of the AD7691 being obsoleted for a very long time you can always upgrade to the AD4000/3 family. In the next year we plan to release the rest of the products in the AD4000 family which will include lower throughput versions like the AD4011 (LFCSP package only) which is 500ksps. The only difference with these parts from the AD7691 is that they require a fixed 1.8V VDD. As long as you have the capability of adjusting the VDD supply to 1.8V then you can upgrade or change parts at a later date to the AD4000 family without respinning your PCB.